A P I M o d e l 1 6 0 8

R e c o rd in g C o n s o le
O p e r a t o r 's M a n u a l

= F E
R

Important Safety Instructions

1.

Please read these instructions

2.

Keep this Manual in a safe place

3.

Do not use this console near water

4.

Clean only with a dry cloth

5.

Do not block any ventilation openings

6.

Do not install near any heat sources such as radiators, heat registers, stoves, or other devices
(including the power supply) that produce heat

7.

Do not defeat the safety purpose of the polarized or grounding type AC plug

8.

Protect both the AC power cord to the power supply and the DC cable between the supply and the
console from being walked on or pinched

9.

Use only attachments/accessories specified by the manufacturer

10.

Unplug this device during lightning storms or when unused for long periods of time

11.

Refer all service to qualified personnel

ATTENTION: Exposure to extremely high noise levels may cause

permanent hearing loss or damage. Individuals vary considerably in
susceptibility to noise-induced hearing loss, but nearly everyone will lose
some hearing if exposed to sufficiently intense noise (or even music) for a
period of time. Be safe.

WARNING To reduce the risk of

fire or electric shock, do not
expose this apparatus to rain or
moisture.

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Introduction
Thank you for choosing APIs 1608 analog mixing console. Whether you are a
newcomer to API or are already a part of the nearly 40-year tradition of API excellence, we
appreciate your purchase.
The 1608 small format recording console is based on the designs of the original API
1604 built in the 70s and early 80s. The success of the 1604 and the continued demand
for a small footprint, high quality console has produced the 1608.
API takes great pride - and great care - in the hand assembly of all our professional
audio products. Above all, we appreciate our loyal users those who create, track, mix,
engineer, master, and produce - who have made the Company what it is today.

API Users Manual v1.3 01-09

API part # 910-0500

Written for Automated Processes Incorporated by Dan Pfeifer 2008 All Rights Reserved

Table of Contents
1.0

Overview

2.0

548B Channel Module

2.1
440B Fader Module
2.2
Mute/Solo Section
2.3
Preamp Section
2.4
Echo/Auxiliary Sends
2.5
Routing and Output Section
2.6
550A Equalizer
2.7
560 Equalizer
2.8
548B Connections

3.0

E1608
3.1
3.2
3.3
3.4

4.0

168B Summing Bus Sub-master Module

4.1
Summing Bus Sub-masters
4.2
168B Connections

5.0

268B Program Bus Output Master and Monitor Output Module

5.1
Program Bus Output Masters
5.2
440B Stereo Master Fader Module
5.3
Monitor Output Controls
5.4
268B Connections

6.0

845B Control Room Monitor Module

6.1
Control Room Monitor Controls
6.2
Control Room Monitor Source Selectors
6.3
845B Connections

7.0

840B Central Facilities Module

7.1
Headphone Amplifier
7.2
Talkback
7.3
Mute Group
7.4
Aux Pre = Mute
7.5
Solo Master
7.6
Channel Meter Control
7.7
Peak Threshold
7.8
Oscillator
7.9
840B Connections
7.10
Headphone Jack

8.0

Meter
8.1
8.2
8.3
8.4
8.5

Echo Send/Return Module

Echo Send Section
Echo Return Section
Echo Return 500 Slots
E1608 Connections

Bridge
Channel/Bus Meters
Left and Right Program Meters
Echo Send/Return Meters
Power Supply Voltage Indicators
Talkback Microphone

9.0

Rear Panel
9.1
548B Channel Module Connections
9.2
E1608 Echo Send/Return Connections
9.2.1 Echo Sends
9.2.2 Echo Returns
9.2.3 Echo Return 500 Slots
9.3
168B Summing Bus Sub-master (ACA) Connections
9.3.1 Summing Bus Sub-master Outputs
9.3.2 Program Bus Mix Inputs
9.4
268B Program Bus/Master Output Connections
9.5
268B Control Room Monitor Output Connections
9.6
845B 6-Track Playback Input Connections
9.7
840B Ancillary Connections
9.7.1 Talkback Remote Port and Oscillator Output
9.7.2 Stereo Headphone Output
9.8
Expander Port
9.9
PSU Connection

10.0

Application Guide
10.1
Multitrack Recording
10.2
Multichannel Mixing
10.3
DAW Hybrid
10.4
E1608 Echo Send Applications
10.5
E1608 Echo Return Applications
10.6
168B Summing Bus and Sub-master Applications
10.7
Echo Return 500 Slot Applications
10.8
Rear Panel DB25 Connection Diagrams

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1.0

Overview

Building on API's rich heritage of extremely high quality recording consoles, we are proud to introduce
the new Model 1608, a full featured small format recording console based on the vintage API 1604
console, which has held its demand and value for over three decades.
The 1608 gives all of the advantages of the 1604 Vintage Consoles while adding new, modern features
valuable to today's Engineers, Producers and Musicians.
Features

16 Input Channels each with Mic Pre and Equalizer

Accepts up to eight API 500 Series Modules

8 Main Buses

8 Auxiliary Buses

1 Stereo Bus

8 Echo Returns with main and stereo bus assign

Full Center Section Control

Analog Metering

5.1 Center Section Monitoring

Comprehensive Rear Patch Connections

The 1608 is built to the same exacting API build standards as our Vision consoles, Legacy consoles, and
modular products.
The standard fit of a 1608 Console is:
16
12
4
8
1
16
1

548B Inputs with Mic/Line and Direct Output

550A Equalizers
560 Equalizers
Echo Returns
Complete Central Facilities Section
Manual Faders
Stereo Fader

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2.0

548B Channel Module

The 548B Channel module provides a single audio path for bringing signals into
the console for mixing and/or routing to external destinations. Together with the
440B Fader, it provides a comprehensive audio path for a variety of applications:

Microphone/instrument/line preamplifier

Equalizer

High-pass filter

Balanced insert

Eight (8) Echo/Auxiliary Sends

Fully featured mute and solo section

Pan-pot

Direct Output

Program and Summing Bus assignments

All eight echo/aux sends can be routed either pre or post-fader. Echo/aux Sends
7/8 can be routed to feed the Summing Buses.
The basic signal flow through the 548B Channel module is as follows:
input preamplifier -> equalizer -> insert -> fader/mute -> output
routing

2.1

440B Fader Module

The 440B Mono Fader is the primary output level control for the channel.
The channel Fader controls the output to the:

Direct Output

Summing Buses

Program Bus

Post-fader Echo/Auxiliary Sends

When the Fader is set to 0dB, the level is at unity gain

Each 440B Mono Fader module contains eight mono Alps 100mm faders and
supports the eight channel modules mounted above it

2.2

Mute/Solo Section
The 548B Channel module provides a comprehensive set of solo and mute controls including:

Channel on/off switch

AFL, PFL, and SIP Solo functions

Solo Safe

Mute Group assignment

The controls for the 548B Mute and Solo function as follows:
SOLO: Activates the selected solo function

The following solo functions may be selected via the 845B

Central Facilities Module:
o Pre-fader Listen (PFL): Non-destructive, mono
o After
Fader
Listen
(AFL):
Non-destructive,
mono/stereo
o Solo-In-Place (SIP): Destructive, panned, post-fader

Illuminates in yellow when engaged

NOTE: PFL is the default solo mode.
NOTE: Channels and Echo Returns must be assigned to the
Program Bus for Solo-In-Place for their mutes to activate when
other channels or Echo Returns are soloed.

SAFE: Activates the Solo Safe mode for that channel

The SAFE button protects that channel from being muted when the Solo-In-Place
function is active and another channel or an Echo Return is soloed.

Illuminates when engaged

MUTE: Cuts the primary audio output

The MUTE button is the on/off switch for the primary channel output and is located postfader in the signal flow

The MUTE button is the numbered button located just above each fader

Illuminates in red when engaged

10

MUTE GRP (Mute Group): Assigns the channel to the master Mute Group

All channels assigned to the master Mute Group will mute when the MUTE GROUP
button on the 845B Central Facilities Module is pressed

Illuminates when engaged

NOTE: If the channel MUTE GRP button and the AUX PRE=MTE button on the 845B
Central Facilities Module are engaged, all pre-fader Echo/Auxiliary Sends will be muted
when the master MUTE GROUP button is engaged.
2.3

Preamp Section
The Preamp section of the 548B provides three audio input options:

Line Input

Microphone Input

Instrument Input
A Peak Indicator is located at the output of the Preamp. The MIC
button serves as the Peak Indicator and turns red when peaks cross
the threshold set on the 840B Central Facilities Module.
Note: The Peak Indication
INSTRUMENT mode.

LED

functions

in

MIC,

LINE

or

Line Input: Accepts balanced, low-impedance, line-level signals from the LINE INPUT connector.
The Line Input has the following features:

-6 dB Pad

Peak Indicator

Polarity Inverter (phase reverse)

Note:

Line Input is the default channel input.

Microphone Input: Accepts balanced, low-impedance, microphone-level signals from the MIC
INPUT connector. Its the classic API 212L microphone preamplifier with the following features:

+65dB of gain

-20 dB Pad

Peak Indicator

Polarity Inverter (phase reverse)

48v Phantom Power

Note:
Note:

The MIC button must be engaged to use this input.

The signal from the Microphone Input is replaced with the signal from the
Instrument Input when a 1/4 plug is inserted in the Instrument Input jack.

Instrument Input: Accepts unbalanced, high-impedance, instrument-level signals from the 1/4"
INSTRUMENT INPUT connector. The Instrument Input reduces the need for separate Direct
Injection (DI) boxes and has the following features:

+45dB of gain

Peak Indicator
Note:

The MIC button must be engaged to use this input.

Note:

The Instrument Input jack is a switching jack. The signal from the Microphone
Input is replaced with the signal from the Instrument Input whenever a 1/4 plug is
inserted in the Instrument Input jack.

Note:

The Pad and Polarity Inverter (Phase Reverse) do not apply to the Instrument
Input. If these functions are needed, the use of an external Direct Injection (DI)
box connected to the Microphone Input is suggested.

11

The controls for the 548B Preamp section function as follows:

No Buttons Engaged: Line Input selected
MIC: Selects the Microphone Preamp as the input for the channel

The MIC button must be engaged for the Instrument Input to

be used

Illuminates in blue when engaged

The MIC button provides a peak Indicator by turning red

whenever the peak threshold is crossed
Note: The signal from the Microphone Input is replaced when a
1/4 plug is inserted in the Instrument Input jack.
GAIN: Provides up to +65dB of gain for the Microphone and +45dB for the Instrument Inputs
Line Input: The gain control does not affect the Line input
48V: Provides 48 Volt Phantom Power to the MIC INPUT XLR connector on the rear panel

Illuminates in red when engaged

PAD: Inserts a -20 Pad for the Microphone or a -6dB pad for Line inputs

Illuminates when engage

: Inserts a Polarity Inverter (Phase Reverse) for the Microphone and Line inputs

Illuminates when engaged

12

2.4

Echo/Auxiliary Sends
The 548B Channel module provides eight fully functional echo/auxiliary sends,
four mono (Sends 1-4) and two stereo (Sends 5/6 and 7/8). Accordingly, the
1608 is equipped with eight balanced Auxiliary Buses and outputs.

Each mono Echo/Auxiliary Send has an individual level control and an

on/off switch

Each stereo Echo/Auxiliary Send has a stereo level control, a pan-pot,

and an on/off switch

Sends 7 and 8 can be routed to feed the 1-4 Summing Buses only in
addition to their Auxiliary Buses

The controls for the 548B mono Echo/Auxiliary Sends 1-4 function as follows:
1 and 2 Level: Individual level controls for Sends 1 and 2
1/2 PRE: Routes the pre-fader signal to Sends 1 and 2

Sends 1 and 2 are fed post-fader when the PRE button is

not engaged

Illuminates when engaged

1 and 2 (buttons): Individual on/off switches for Sends 1 and 2

Illuminates when engaged

3/4 Level: Individual level controls for Sends 3 and 4
3/4 PRE: Routes the pre-fader signal to Sends 3 and 4

Sends 3 and 4 are fed post-fader when the PRE button

is not engaged

Illuminates when engaged

3 and 4 (buttons): Individual on/off switches for Sends 3 and 4

Illuminates when engaged

The controls for the 548B stereo Echo/Auxiliary Sends 5/6 and 7/8 function as follows:
5/6 LVL: Stereo level control for Sends 5 and 6
5/6 PAN: Pan-pot for Sends 5 and 6
5/6 PRE: Routes the pre-fader signal to Sends 5 and 6

Sends 5 and 6 are fed post-fader when the PRE button is

not engaged

Illuminates when engaged

5/6 (button): On/off switch for Sends 5 and 6

Illuminates when engaged

7/8 LVL: Stereo level control for Sends 7 and 8
7/8 PAN: Pan-pot for Sends 7 and 8
7/8 PRE: Routes the pre-fader signal to Sends 7 and 8

Sends 7 and 8 are fed post-fader when the PRE button is

not engaged

Illuminates when engaged

7/8 (button): On/off switch for Sends 7 and 8

Illuminates when engaged

13

TO BUS: Routes the output of stereo Send 7 and 8 directly to the Summing Bus 1-4 assignment
section. When TO BUS is engaged the send functions as follows:

Auxiliary Buses 7 and 8 are fed in addition to the Summing Bus 1-4 assignment section

Auxiliary Sends 7 and 8 cannot access the Program Bus from the channel module

The 7/8 on/off button is bypassed for the feed to the Summing Busses, but is still active for
the feed to Auxiliary Buses 7 and 8

The 7/8 PRE button may be used

The 7/8 stereo level control and pan-pot are active

The channel output pan-pot is bypassed for Summing Bus assignments from Send 7/8

Illuminates when engaged

2.5

Routing and Output Section

The routing and output section of the 548B Channel module provides a
comprehensive set of routing and output functions including:

Insert

High-pass filter

Switchable panning

Bus assignments

Direct Output
The output section provides three simultaneous audio output options:

Direct Output: Direct balanced line output

Summing Buses: Any of eight summing buses (ACA)

Program Bus: The Left and Right stereo Program Bus (PGM)

Direct Output: The Direct Output feeds the channel output signal to the DIRECT OUTPUT on the
rear panel. The Direct Output has the following features:

The Direct Output is fed post-fader

The Direct Output is always active except when the channel MUTE is engaged

Balanced, line-level output at the DIRECT OUTPUT XLR connector

Summing Buses: The channel output may be assigned to one or more of the eight Summing
Buses or Active Combining Amplifiers (ACA). Some possible applications of the Summing Buses
include:

Multitrack channel assignments

Multitrack summing

5.1 mixing

Additional channel outputs

Additional echo/auxiliary sends

Sub-grouping
The summing buses (ACA) include the following features:

Individual Summing Bus assignments from the 548B modules

Switchable Odd/Even Summing Bus panning on the 548B modules

Routing from Echo/Auxiliary Sends 7 and 8 on the 548B modules

Individual on/off, calibration, trim, solo, and Program Bus assignment controls on the
168B module

Balanced, line-level outputs at the BUS OUTPUT 1-8 (ACA OUTPUT) sub-D connector
Program Bus: The channel output can be routed to the Program Bus (also ACA) for stereo
mixing and for the Left and Right channels of a 5.1 mix. The Program Bus includes the following
features:

Program Bus assignment from the 548B modules

Program Bus Insert via the 268B module and rear panel connections

440B Stereo Master Fader

Individual Left and Right program channel on/off, calibration, and trim controls

Balanced, line-level outputs via the LEFT and RIGHT PROGRAM OUTPUT XLR connectors

14

The controls for the 548B Routing and Output section function as follows:
PAN (pan-pot): Provides continuous panning control

Stereo panning between the Left and Right Program Buses

Odd and Even panning between Summing Buses (when

engaged)
PAN (button): Activates Odd/Even panning between the assigned
Summing Buses

The PAN button must be engaged to enable summing bus

panning

The PAN button only applies to summing bus panning and does
not affect Program Bus Left/Right panning

Illuminates when engaged

PGM (Program): Assigns the channel output to the Program Bus

The Program Bus is fed post the channel pan-pot

Illuminates when engaged

FLTR (Filter): Activates the channel output high-pass Filter

-3 dB at 50Hz

6 dB/octave slope

Illuminates when engaged

The channel output Filter is located post the Fader wiper and pre the Fader amplifier
Note: An additional band-pass filter is available on channels equipped with 550A Equalizers.
INS (Insert): Activates the channel Insert Return

The Insert Send is fed pre-fader from the output of the Equalizer

The Insert Send is always active

The Insert Send is a balanced, line-level signal routed to the INSERT SEND
(EQUALIZER OUTPUT) 1/4 tip-ring-sleeve jack on the rear panel

The Insert Return accepts a balanced, line-level signal from the INSERT RETURN
(FADER INPUT) 1/4 tip-ring-sleeve jack on the rear panel

The Insert Return is located post-EQ and pre-fader

The Insert Return is active only when the INS button is engaged

Illuminates when engaged

Trim-pot: The trim-pot below the channel pan-pot calibrates the FADER IN to the DIRECT
OUTPUT stage so the path is exactly at unity gain with the channel fader set to 0dB.
Summing Bus (ACA) Assignment 1-8: Assigns the channel output
to one or more of the eight Summing Buses (Active Combining
Amplifiers).

Assignments to the Summing Buses can be made on an

individual basis

Summing Buses are fed post-fader or post the channel panpot when its engaged

Summing Bus assignments are only active when engaged

Switchable Odd/Even Summing Bus panning

The Summing Buses 1-4 can be fed pre or post fader from
Echo/Auxiliary Sends 7 and 8

15

2.6

550A Discrete 3-Band Equalizer

The legendary API 550A Equalizer is installed on channels 1-12 in the standard 1608
configuration.

Features

3 bands of classic API equalization

Each band offers 7 API selected frequency centers
Reciprocal and repeatable filtering
maximum 12 dB of boost/cut per band
EQ Band 1 and 3 offer shelf/peak switching
"Proportional Q" narrows filter Q at extremes
Traditional API fully discrete circuit design
High headroom +30 dB clip level

Few equalizers enjoy the respect and admiration of the coveted API 550A.
Designed by the now legendary Saul Walker in the late 60's, the discrete
550A was first used as a modular OEM equalizer. As the industry rapidly
embraced the sonic quality of the 550A, it quickly found its way into many
custom console designs of the era. Many of these consoles are still in use
today.
Forty years later, the 550A remains the standard against which other EQs
are measured, and it has played a major role in the recording industry for
decades. Still copied but never duplicated, the 550A became API's standard
channel module EQ when the company began manufacturing consoles in
1971. With virtually all existing units spoken for, popular demand for this EQ
resulted in API resuming production in 2004.

The 550A provides reciprocal equalization at 15 points in 5 steps of boost to a maximum of

12dB of gain at each point. The fifteen equalization points are divided into three overlapping
ranges. The high and low frequency ranges are individually selectable as either peaking or
shelving, and a band-pass filter may be inserted independently of all other selected equalization
settings. Frequency ranges and boost/cut are selected by three dual-concentric switches, and a
pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle
switch is used to insert the band-pass filter into the 550A.
The combination of Walker's incomparable 2520 op amp, and his "Proportional Q" circuitry gives
the 550A user an uncomplicated way to generate acoustically superior equalization.
With the long-awaited reissue of this unit, an EQ that has had such a part in the history of
recording is continuing to make history in today's music.

WARNING WARNING WARNING WARNING WARNING

The use of NON-VPR Alliance approved 500 series modules in the 1608 is vehemently
discouraged, and may cause operational difficulties with the console. Improper
operation, excessive current draw and poor module fit are all potential issues with
these devices.
For the most recent
www.apiaudio.com.

list

of

VPR

Alliance

approved

modules,

please

visit

API reserves the right to deny warranty claims when non-VPR Alliance 500 series
modules are used.

16

2.7

560 Discrete 10-Band Graphic Equalizer

The classic API 560 Equalizer is installed on channels 13-16 in the standard 1608 configuration.

Features

10 bands of API proprietary equalization

Familiar graphics operation on one octave centers
12 dB of boost/cut per band
"Proportional Q" narrows filter Q at extremes
Additional resolution within the 4 region
Center detent for reliable reset
Silent bypass button
Re-issue of the 1969 API 560 EQ

Originally conceived for use in API Consoles of the 60's and 70's, the API
560 is a unique device designed to accomplish tasks that no other EQ can. It
delivers that "one-of-a-kind" API sound, precision easy set filtering, and high
headroom in a very small package. Extremely fast to set and reset using
accurate zero detents, the curve shaping potential of the 560 is unmatched.
At home both in field recording and the studio environment, this "new-old"
560 is true to the original 560 with improved resolution in the critical area of
4 dB. Incorporating API's exclusive circuitry and proprietary components
(such as the legendary 2520 op-amp), the 560 artfully blends the past with
presentlayout with function.

The API 560 was created to fit all applications for the professional engineer. For most of the 70's
and 80's, every remote recording console that API manufactured used this versatile graphic EQ.
It is also ideal for studio and live sound applications, where a professional result is required. The
current 560 design has been taken from the original blue prints and spec control drawings from
the API archives.
The large number of available EQ bands make the 560 an ideal companion to parametric EQ, as
well as ideal for signal sweetening and room tuning. Not lacking in features, the 560 makes use
of API's unique "Proportional Q" design introduced by API in the 60's, intuitively widening the
filter bandwidth at lower boost/cut levels and narrowing it at higher settings. In addition, boost
and cut characteristics are identical, so previous actions can be undone.
The extraordinary headroom made possible with API's proprietary 2520 op-amp offers
predictable and wonderful "analog" performance under duress. With a wider range of 500
mounting options, the 560 is a valuable asset to your performance-critical applications.
The 560 Graphic Equalizer exhibits the reliability, long life, and uniformity which are
characteristic of API products.

WARNING WARNING WARNING WARNING WARNING

The use of NON-VPR Alliance approved 500 series modules in the 1608 is vehemently
discouraged, and may cause operational difficulties with the console. Improper
operation, excessive current draw and poor module fit are all potential issues with
these devices.
For the most recent
www.apiaudio.com.

list

of

VPR

Alliance

approved

modules,

please

visit

API reserves the right to deny warranty claims when non-VPR Alliance 500 series
modules are used.

17

2.7

548B Connections
The rear panel connections for the 548B Channel module are as follows:

DIRECT OUTPUT:

Balanced, Line-level

Male XLR

INSERT

RETURN (FADER INPUT):

Balanced, Line-level
1/4 tip-ring-sleeve switching jack
Replaces the EQ Out signal when a jack is inserted
and the INS button is engaged

INSERT

SEND (EQUALIZER OUT):

Balanced, Line-level
1/4 tip-ring-sleeve switching jack
The feed to the Insert Return (Fader Input) is
defeated when a jack is inserted

EQUALIZER INPUT:

Balanced, Line-level

1/4 tip-ring-sleeve switching jack

The Preamp Output signal is replaced with this signal

when a jack is inserted
PREAMP

OUTPUT:
Balanced, Line-level
1/4 tip-ring-sleeve jack
Half-normalled to feed the Equalizer Input

INSTRUMENT INPUT:

Unbalanced, High-impedance

Instrument-level

1/4 tip-sleeve switching jack

The Microphone Input signal is replaced with this

signal when a jack is inserted
MIC INPUT:

Balanced, Low-impedance

Microphone-level

Female XLR connector

LINE INPUT:

Balanced, Low-impedance

Line-level

Female XLR connector

18

3.0

E1608 Echo Send/Return Module

The E1608 Echo Send/Return module serves multiple
contributes greatly to the extensive flexibility of the 1608.
applications of the Echo Send/return module include:

Echo returns from reverbs and effect units

Additional line-level inputs during tracking or mixing

Audio sub-grouping

Echo send masters

Cue and foldback send masters

Mix minus matrixes

Parallel processing

functions and
Some possible

The E1608 Echo Send/Return module has two primary sections:

Echo Send

Echo Return

19

3.1

Echo Send Section

The E1608 ECHO SEND section primarily functions as an echo send

master. It can also provide grouping functions when used with the
echo sends, external inputs, and the Echo Return section.
It is possible to combine an external audio input with the Echo Bus
at the input of the Echo Send section.

The Echo Send section has the following features:

Flexible input sources (including a combined external input)

On/off switch

Level control

Solo (AFL only)

Talkback insertion for cue/foldback sends (headphone sends)

Routing to the Echo Return section

Balanced, line-level output at the ECHO SENDS OUTPUT 1-8 sub-D connector
The Echo Send section can be fed from two simultaneous sources:

Auxiliary Bus: The output of its corresponding Echo Sum Bus

and/or

External Input: ECHO SEND EXTERNAL INPUT 1/4 tip-ring-sleeve jack

Echo Send Master: The Echo Send Master is the master control level for its corresponding Echo
Send Bus.
External Audio Input: In addition to the normal feed from its corresponding Echo Sum Bus, the
Echo Send can accept a balanced, line-level input from the corresponding ECHO SEND
EXTERNAL INPUT 1/4 tip-ring-sleeve jack on the rear panel. This signal is added to the output
from the corresponding Echo Sum Bus when the EXT IN button is engaged.
IMPORTANT NOTE: When the EXT IN button is engaged, the external input is combined with the
output from the corresponding Echo Sum Bus and is fed to the input of the Echo Send section.
Regardless of the input source, the balanced, line-level output of the Echo Send is fed to the
ECHO SENDS OUTPUT 1-8 sub-D connector on the rear panel for connection to effects devices,
cue/foldback systems, and so on. This output is active whenever the corresponding Echo Send
is turned on.
The output of the Echo Send can be selected as the input to its corresponding Echo Return
section for additional routing to the Program or Summing Buses. This is done by engaging the
MIX button in the Echo Return section. This can be very useful for creating sub-groups, mix
minus cue feeds, and other applications.
The output of the Echo Send is also fed to its corresponding meter in the Meter Bridge (E1-E8).
The output of the Echo Return section can be sent to the meter instead by engaging the VU RET
button.

20

The controls for E1608 Echo Send section function as follows:

AFL: Activates an AFL solo

Illuminates when engaged

ON: On/off switch for the Echo Send

Illuminates in green when engaged

LEVEL: Controls the output level of the Echo Send

VU RET (Return): Routes the output of the Echo Return section to the meter in place of the
output from the Echo Send.

Illuminates when engaged

T/B (Talkback): Allows the Talkback microphone to feed the Echo Send when the Talkback
microphone is activated

Illuminates in blue when engaged

EXT IN (External): Mixes the ECHO SEND EXTERNAL INPUT from the rear panel with the output
from the corresponding auxiliary bus at the input of the Echo Send

Illuminates when engaged

NOTE: There are two trim-pots on the odd number Echo Send/Return sections. These are not
labeled, but trim the calibration for respective Echo Sends.
3.2

Echo Return Section

The E1608 ECHO RETURN section is an independent audio channel
with multiple input options, complete level, muting, and panning
controls, full solo capabilities, and full routing to the Program and
Summing Buses. Some possible Echo Return applications include:

Return path for external devices (multitracks, reverb/effects

units, etc.)

Input path for tracking, overdubs, and virtual instruments

Audio Sub-grouping (when used with the Echo Send section)

5.1 mixing
The Echo Return section has the following features:

Multiple input sources (including a switchable auxiliary

external input)

On/off switch

Level control

Switchable pan-pot

Solo (PFL, AFL, SIP)

Solo Safe

Patchable 500 Slot for 500 Series modules

Routing from the Echo Send section

Output assignments to the Program and Summing Buses

(ACA)
The Echo Return section can be fed from one of three sources:

Echo Returns Input: ECHO RETURNS INPUT 1-8 sub-D

connector

Echo Return Auxiliary Input: ECHO RETURNS AUX INPUT 18 1/4 tip-ring-sleeve jack

Echo Send Output: The output of the Echo Send section

21

Echo Returns Input: Accepts the balanced, line-level input from the ECHO RETURNS INPUT 1-8
sub-D connector on the rear panel.

The Echo Returns connector is the default input for the Echo Return

Echo Return 500 Slots are normalled between the Echo Returns Input connector and the
input to the Echo Return module
o The signal from the Echo Return Input connector is fed through the
corresponding Echo Return 500 Slot before being fed to the Echo Return module
input.
o If engaged, a module mounted in the slot will process the audio before it arrives
at the Echo Return module
o If a slot is empty, the signal will loop through the slot to feed the corresponding
Echo Return input when a Bypass Card is inserted into the card edge connector
of the corresponding slot. (These cards are supplied by API when the console is
delivered without 500 modules in any 500 slot)
o
o

o
Note:

The modules in the Echo Return 500 Slots may be used elsewhere by using the
ECHO RETURN 500 SLOT INPUT and OUTPUT patch points on the rear panel
Inserting a plug into the ECHO RETURN 500 SLOT INPUT jack will defeat the
signal from the Echo Return Input connector, but the output of the slot is still
sent to the Echo Return module
The Echo Return 500 Slot may be bypassed by using the Echo Return Auxiliary
Input
Please refer to section 3.3 Echo Return 500 Slots for further information.

Echo Returns Auxiliary Input: Accepts the balanced, line-level input from the ECHO RETURNS
AUX INPUT 1/4 connector on the rear panel. The Echo Return Aux Input signal will replace the
Echo Return and Echo Send (MIX) signals when the AUX IN button is engaged.
Echo Send Output: Routes the output of the Echo Send section to the input of the Echo Return
section. The Echo Send output will replace the Echo Return signal when the MIX button is
engaged.
The Echo Return section provides two simultaneous audio output options:

Summing Buses: Any of eight Summing Buses (ACA)

Program Bus: The Left and Right Program Bus (PGM).

Summing Buses: The channel output may be assigned to one or more of the eight Summing
Buses or Active Combining Amplifiers (ACA).
Program Bus: The channel output can be routed to the Program Bus (also ACA) for stereo
mixing and for the Left and Right channels of a 5.1 mix.

22

The controls for the E1608 Echo Return output section function as follows:
Summing Bus (ACA) Assignment 1-8: Assigns the Echo Return
output to one or more of the eight Summing Buses (Active
Combining Amplifiers)

Assignments to the Summing Buses can be made on an

individual basis

Summing Buses are fed post the Echo Return level control
or post the Echo Return pan-pot when its engaged

Summing Bus assignments are only active when engaged

Switchable Odd/Even Summing Bus panning

The Summing Bus assignment buttons illuminate when

engaged
LVL (Level): Controls the output level of the Echo Return
PAN (pan-pot): Provides continuous panning control

Stereo panning between the Left and Right Program Buses

(when engaged)

Odd and Even panning between Summing Buses (when

engaged)
PAN (button): Activates Left/Right panning between the Program
Buses and Odd/Even panning between the assigned Summing
Buses

The PAN button must be engaged to enable Summing and

Program Bus panning

Illuminates when engaged

Important Note: Unlike the pan-pot in the 548B Channel module, the PAN button must be
engaged to enable Left/Right Program Bus panning.
PGM (Program): Assigns the Echo Return output to the Program Bus

The Program Bus is fed post the Echo Return pan-pot

Illuminates when engaged

SOLO: Activates the selected solo function for that Echo Return

The following solo functions may be selected via the 845B Central Facilities Module:
o Solo(PFL): Non-destructive, mono, pre-fader listen (PFL). This is the default
solo mode.
o After Fader Listen (AFL): Non-destructive, mono, after-fader listen
o Solo-In-Place (SIP): Destructive, panned, after-fader listen

Illuminates in yellow when engaged

NOTE: PFL is the default solo mode.
NOTE: Channels and Echo Returns must be assigned to the Program Bus for Solo-In-Place
for their mutes to activate when other channels or Echo Returns are soloed.
SAFE: Activates the Solo Safe mode for that Echo Return

The SAFE button protects that Echo Return from being muted when the Solo-In-Place
function is active and another channel or Echo Return is soloed.

Illuminates when engaged

MUTE: Cuts the audio output from that Echo Return

The MUTE button is the on/off switch for the Echo Return output and is located post
level control in the signal flow

The MUTE button is the button with an E and a number (1-8) located in the Echo
Return section

Illuminates in red when engaged

23

AUX IN: Selects the Echo Return Auxiliary Input as the input for the Echo Return

Illuminates when engaged

NOTE: The signals from the Echo Return Input and Echo Send Output (MIX) are
defeated when the AUX IN button is engaged.
MIX: Selects the Echo Send output as the input for the Echo Return

Illuminates when engaged

NOTE: The signal from the Echo Return Input is defeated when the MIX button is
engaged.
3.3

Echo Return 500 Slots

The console is equipped with eight Echo Return 500 Slots. These 500 Slots are built to power
and interface any API 500 Series module:

512C Preamplifier

525 Compressor

550A 3-Band EQ

550B 4-Band EQ

560 Graphic EQ
Some possible applications of the 500 Slots include:

Extra microphone/instrument inputs (when equipped with a 512C Preamp)

Extra signal processing for the Echo Return inputs

Patchable signal processing for use in the channel Inserts and patch points

Patchable signal processing for use in the Program Bus Inserts

Patchable signal processing for use anywhere else (internally, externally, etc.)
When equipped with a 512C Preamp, the 500 Slot and Echo Return combine to form a powerful
input module capable of routing a microphone, instrument, or line input to the Program and/or
Summing Buses with full assignment, panning, and solo functions. This can greatly expand the
capabilities of the console for almost all applications.
When equipped with a 512C Preamp, an API EQ, and a 525 Compressor, three 500 Slots can be
used to create a single high-quality signal path for direct feed to the multitrack recorder or
DAW.
As indicated by these examples, the 500 Slots can be custom configured to add versatility and
maximize performance.
The features of the 500 Slots are as follows:

All eight 500 Slots are empty in the standard 1608 configuration and equipped with
Bypass Cards

500 Slots can deliver 48v phantom power to the Echo Return Input connector if
equipped with a 512C Preamp

The slots are normalled between the Echo Returns Input connector and the inputs to the
Echo Return modules

If engaged, the module mounted in a slot will process the audio before it arrives at the
Echo Return module input

If a slot is empty, the signal will loop through the slot to feed the corresponding Echo
Return module input

The modules in the Echo Return 500 Slots may be used elsewhere by using the ECHO
RETURN 500 SLOT INPUT and OUTPUT patch points on the rear panel

Inserting a plug into the ECHO RETURN 500 SLOT INPUT jack will defeat the signal from
the Echo Return Input connector, but the output of the slot is still sent to the Echo
Return module

The 500 Slot may be bypassed by using the Echo Return Auxiliary Input

24

3.4

E1608 Connections
The rear panel connections for the E1608 Echo Send/Return module are as follows:

ECHO SENDS EXTERNAL INPUT 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve jack

ECHO SENDS OUTPUT 1-8:

Balanced, Line-level

Female 25-Pin Sub-D connector

ECHO RETURNS AUX INPUT 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve jack

ECHO RETURNS INPUT 1-8:

Balanced, Line-level

Female 25-Pin Sub-D connector

ECHO RETURNS 500 SLOTS IN 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve switching jack

The signal from the Reverb Return Input

connector is replaced with this signal when a jack
is inserted
ECHO RETURNS 500 SLOTS OUT 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve jack

Also normalled to feed the Echo Return module

input

25

4.0

168B Summing Bus Sub-master Module

The 168B Summing Bus Sub-master Module provides control and routing for
the eight Summing Buses, also known as Active Combining Amplifiers (ACA).
The following is provided for each Summing Bus (ACA):

On/off switch

Solo (PFL and AFL only)

Trim control

ACA calibration

Individual Left and Right Program Bus assignments

Balanced, line-level outputs

26

4.1

Summing Bus Sub-masters

The Summing Bus Sub-masters (labeled SUB 1-8) are the final stage before the Summing Bus
outputs are fed to the BUS OUTPUT 1-8 (ACA OUTPUT) sub-D connector on the rear panel. The
output of the Summing Bus Sub-masters (SUB 1-8) can also be routed to the Program Bus via
individual Left and Right assignment buttons.
The controls for each 168B Summing Bus Sub-master (SUB 1-8) function as follows:
L and R PGM ASSIGN: Individual assignment of the Summing Bus
(ACA) output to the Left and Right Program Buses

The Left and Right Program Bus Assignment switches are

actually fed from the PGM BUS MIX INPUT jacks on the rear
panel
o These jacks are normalled to the output of the
Summing Buses (ACA), but break that connection when
a jack is inserted
o The normal or inserted signal present at the PGM BUS
MIX INPUT jack feeds the Left and Right Program
(PGM) Bus Assignment switches

Illuminates when engaged

NOTE: Sub-masters assigned to the Program Bus will mute if the console is in Solo-In-Place
and a channel or Echo Return is soloed.
SOLO: Activates the PFL or AFL Solo function

Illuminates when engaged

ON: On/off switch for the Summing Bus Sub-master (SUB 1-8)

Illuminates in when engaged

Provides max kill in off position with TRIM fully clockwise (this is the calibrated
position of the Send)
TRIM: Serves as a 0dB to -84dB trim control for the Bus Out application or 0dB to -30dB trim
control for Return to Program Bus

Cut only (calibrate level to infinite cut)

CAL (trim-pot): The trim-pot calibrates the output of the Active Combining Amplifier

4.2

168B Connections
The rear panel connections for the 168B Summing Bus Sub-master module are as follows:

PGM

BUS MIX INPUT:

Balanced, Line-level
1/4 tip-ring-sleeve jack
Replaces the Summing Bus output signal at the
Left and Right Program Assignment switches
when a jack is inserted

BUS OUTPUT 1-8 (ACA OUTPUT):

Balanced, Line-level

Female 25-Pin Sub-D connector

27

5.0

268B Program Bus Output Masters and Monitor Output Module

The 268B Program Bus Output Masters and Monitor Output module provides
three functions:

Program Bus Output controls

Monitor Output controls

Program Insert Control

28

5.1

Program Bus Output Masters

Together with the 440B Stereo Master Fader, the Program Bus Output
Master section of the 268B provides a fully featured stereo master
channel. Features of this master channel include:

On/off switch

Trim control

ACA calibration

Output Booster calibration

Switchable balanced insert

Balanced, line-level outputs

The Program Bus Insert Send ACA jacks are the pre-fader Outputs of
the Program Summing Buses. They normally feed the top of the fader
and are half-normalled to the Program Bus Insert Return jacks. The
Program Insert jacks feed the Master Fader and Program Bus Outputs
by engaging the Program Bus Insert switch. The Program Summing Bus
outputs will feed the Program Master fader unless the Program Insert
button is engaged. This allows insertion of external processing
equipment pre Program Fader.

The controls for the 268B Left and Right Program Bus Output Masters (PGM L and PGM R)
function as follows:
ACA CAL (trim-pot): The trim-pot calibrates the output of the
Active Combining Amplifier
BSTR CAL (trim-pot): The trim-pot calibrates the output booster
TRIM: Controls the output level of the Program Bus (ACA)

-5.5bB to +1.5dB
ON: On/off switch for the Program Bus Output Master
PRG INS (Program Insert): Activates the Left and Right Program
Insert Return

The Program Insert Send is fed pre-fader from the output of

the Program ACA

The Program Insert Send is always active

The Program Insert Send is a balanced, line-level signal

routed to the PROGRAM BUS INSERT SEND (ACA OUTPUT)
1/4 tip-ring-sleeve jack on the rear panel

The Program Insert Return accepts a balanced, line-level

signal from the PROGRAM BUS INSERT RETURN (FADER
INPUT) 1/4 tip-ring-sleeve jack on the rear panel

The Program Insert Return is located post-ACA and pre-fader

The Program Insert Return is active only when the INS button
is engaged

29

5.2

440B Stereo Master Fader Module

The 440B Stereo Master Fader feeds the Left and Right Program Outputs of
the console. It is the main stereo output and provides the Left and Right
outputs for 5.1 mixing.

At 0VU the fader is at unity gain

5.3

Monitor Output Controls

The 268B Monitor Output section supports one set of main 5.1
monitors and two sets of stereo monitors. The Monitor Output
section provides on/off switching and calibration for a 5.1 (Left,
Right, Center, Left Surround, Right Surround, and LFE) main
monitor system (MAIN) and the two stereo nearfield monitor
systems (SMALL 1 and 2). The Monitor Output section has the
following features:

On/off switch for all six Monitor Outputs

5.1 Main monitor trim control

Stereo Small 1 trim control

Stereo Small 2 trim control

Balanced, line-level outputs

The Monitor Output section is the final stage before the selected
monitor output is fed to the Control Room Output connectors on
the rear panel. There are a set of controls for each of the six
individual Monitor Outputs that support the 5.1 and stereo monitor
systems:

CR L: Control Room Left

CR R: Control Room Right

CR SL: Control Room Left Surround

CR SR: Control Room Right Surround

CR C: Control Room Center

CR LFE: Control Room LFE (subwoofer)

The controls for each 268B Monitor Output function as follows:

ON: On/off switch for the Monitor Output
MAIN CAL (trim-pot): The trim-pot calibrates the corresponding Main Monitor Output level
SMALL 1 CAL (trim-pot): The trim-pot calibrates the corresponding Small 1 Monitor Output level
(CR L and CR R only)
SMALL 2 CAL (trim-pot): The trim-pot calibrates the corresponding Small 2 Monitor Output level
(CR L and CR R only)

30

5.4

268B Connections
The rear panel connections for the 268B Program Bus Output Master and Monitor Output
module are as follows:

PROGRAM BUS INSERT SEND (ACA OUTPUT):

Balanced, Line-level

1/4 tip-ring-sleeve jack

Half-normalled to Program Insert Return

PROGRAM BUS INSERT RETURN (FADER INPUT):

Balanced, Line-level

1/4 tip-ring-sleeve jack

Replaces the Program Insert Send signal when a jack is

inserted and the PRG INS button is engaged

PROGRAM BUS OUTPUT LEFT and RIGHT:

Balanced, Line-level

Male XLR

SMALL 2 CONTROL ROOM OUTPUTS LEFT and RIGHT:

Balanced, Line-level

Male XLR

SMALL 1 CONTROL ROOM OUTPUTS LEFT and RIGHT:

Balanced, Line-level

Male XLR

MAIN CONTROL ROOM OUTPUTS LEFT, CENTER, RIGHT:

Balanced, Line-level

Male XLR

MAIN CONTROL ROOM OUTPUTS LEFT SURROUND, CENTER,

RIGHT SURROUND:

Balanced, Line-level

Male XLR

31

6.0

845B Control Room Monitor Control Module

The 845B Control Room Monitor Control module provides two functions:

Selection and volume control of the Control Room Monitor system

Selection of the Control Room Monitor input source

32

6.1

Monitor Control Section

845B Monitor Control section provides a comprehensive set of controls for up to three Control
Room Monitor systems. Features include:

Monitor volume control

Monitor cut

Control Room monitor dim with level control

Monitor system selectors

Switchable mono summing

The 845B Monitor Control section functions as follows:
MONO: Sums the Left and Right Control Room Monitor output to
mono.

The MONO button works with all monitor selections

Illuminates in red when engaged

SMALL1/SMALL2: Selects between the Small 1 and 2 Monitor
systems when the MAIN monitor button is disengaged

Supports two stereo monitor systems

Routes the Monitor feed to the Small2 when engaged

Routes the Monitor feed to the Small1 when not engaged

Only active when the MAIN button is not engaged

Illuminates in yellow when active

o Illuminates slightly brighter when engaged
MAIN: Routes the Control Room Monitor feed to the Main monitor
outputs

Supports one stereo or 5.1 monitor systems

Routes the Control Room Monitor feed to the Small monitor

selector when not engaged

Illuminates in yellow when engaged

MON CUT (Monitor Cut): Cuts the Control Room Monitor feed

On/off switch for the Control Room Monitor section

Illuminates in red when engaged

CR DIM (Control Room Dim button): Attenuates the Monitor output
by routing the Monitor feed through the DIM attenuation pot

The CR DIM level is set by the DIM pot

CR DIM is automatically engaged when:

o The TO BUS button is engaged on the Oscillator
o Any of the Talkback buttons (T/B ALL, T/B TO AUX, or
SLATE) are engaged

Illuminates in red when engaged

CONTROL ROOM MONITOR LEVEL: Controls the output level of the Monitor Control section

Volume control for the selected monitor system

The largest and most dangerous knob on the consoleplease use it wisely!

33

6.2

Monitor Source Selectors

The 845B Monitor Source Selectors (CR SOURCE) provide a choice of nine different sources to
feed the Control Room monitors. The selections are divided into three categories:

Program Bus (PGM BUS)

Echo Sends

Six Channel Playback (6 TRK PLAYBACK)

The 845B Monitor Source Selectors function as follows:

6 TRK PLAYBACK 6TKAUX, 6TK1, 6TK2, 6TK3: Routes the signal

from the selected six-track playback source to the Monitor Control
section

The input from the selected external six track playback

source connector on the rear panel is fed to the Monitor
Control section

The selected 6-Track Playback button illuminates in red when

engaged

6 TRK PLAYBACK 6TKAUX is currently inactive and is reserved

for future use

ECHO SENDS 1/2, 3/4, 5/6, 7/8: Routes the output of the selected
Echo Send to the Monitor Control section

The Echo Send output is fed to the Monitor Control section

The selected Echo Send button illuminates when engaged

PGM BUS (Program Bus): Routes the output of the Program Bus
Output Masters to the Monitor Control section

The output from the Program Bus Output Masters are fed to
the Monitor Control section post the Stereo Master Fader

Illuminates when engaged

34

6.3

845B Connections
The rear panel connections for the 845B Control Room Monitor Control module are as follows:
6 TRACK PLAYBACK 1 LEFT and RIGHT Input:

Balanced, Line-level

Female XLR connectors

Left and Right are paralleled with input with

Sub-D connector
6 TRACK PLAYBACK INPUTS 1, 2, and 3:

Left, Center, Right, Left Surround, Right

Surround, LFE

Balanced, Line-level

Female 25-Pin Sub-D connector

6 Track Playback 1 is paralleled with the Left

and Right XLR connectors

35

7.0

840B Central Facilities Module

The 840B Central Facilities provides several ancillary console functions. The
control sections are included for the following functions:

Headphone amplifier

Talkback controls

Mute Group controls

Master Solo controls

Meter control

Peak indicator controls

Oscillator

36

7.1

Stereo Headphone Amplifier

The 840B Stereo Headphone Amplifier is designed for use by the engineer or others in the
Control Room. It has the following features:

On/off switch

1/4 stereo headphone jack (located under the armrest)

Feeds the current Control Room Monitor source from Monitor Control section
o Volume follows the Monitor Control level
o Mono summing is available
o CR DIM is available
o Not affected by the MON CUT or Monitor System Selectors
The 840B Stereo Headphone Amplifier control functions as follows:

ON: On/off switch for the Stereo Headphone Amplifier

Illuminates when engaged

7.2

Talkback
The 840B Talkback section provides a complete set of Talkback routing options and controls. It
has the following features:

Talkback to all

Talkback to auxes only

Talkback microphone level

Independent Slate function with level control

Talkback Microphone in Meter Bridge

Talkback remote control port

The 840B Talkback controls function as follows:
SLATE: Routes Talkback to the Program and Summing Buses

The Left and Right Program Bus Output Masters must be turned
ON with the level up to enable Talkback to feed the Program
Buses

The eight Summing Bus masters (SUB 1-8) must be turned ON

with the level up to enable Talkback to feed the Summing
Buses

Independent Level Control

Momentary Switch

Automatically engages the CR DIM function when pressed

Illuminates in red when engaged

Note: The SLATE function does not include a tone or oscillator feed.
SLATE LEVEL: Volume control for the Talkback to the Program and
Summing Buses

Located adjacent to the SLATE button

T/B TO AUX (Talkback to Auxiliaries): Routes Talkback to the enabled Auxiliary Buses

The E1608 Echo Send T/B button must be engaged to enable Talkback to feed the
corresponding Auxiliary Bus

The Echo Send must be turned ON with the level up to enable Talkback to feed the
corresponding Auxiliary Bus

Momentary switch

Independent level control

Automatically engages the CR DIM function when pressed

Illuminates in yellow when engaged

37

T/B TO AUX LEVEL: Volume control for the Talkback to the enabled Auxiliary Buses

Located adjacent to the T/B TO AUX button

T/B ALL (Talkback to All): Activates the SLATE and T/B TO AUX functions

Routes Talkback to the Program and Summing Buses

Routes Talkback to the Auxiliary Buses

Momentary switch

Automatically engages the CR DIM function when pressed

Illuminates in yellow when engaged

T/B MIC CAL (trim-pot): Calibrates the Talkback microphone level
7.3

Mute Group
The 840B Mute Group section provides one Mute Group with the following features:

Control of the Mute switches on assigned 548B Channel modules

The pre-fader Echo/Auxiliaries of assigned channels may be added to the Mute Group
The 840B Mute Group controls function as follows:
MUTE GROUP: Mutes all channels assigned to the Mute Group

Assigned channels will be muted when the master MUTE

GROUP button is engaged

Channels may be assigned to the Mute Group on an

individual basis by engaging the MUTE GRP button

Assigned channels may be muted independently of the

Mute Group

Assigned channels may not be independently unmuted

when the master MUTE GROUP button is engaged

Illuminates in red when engaged

7.4

AUX PRE=MTE (Auxiliary Pre = Mute): Causes Channel Echo Sends in pre-Fader mode to
follow the Channel Mute

7.5

Solo Master
The 840B Solo Master section selects the solo function for the Channels and Echo Returns. The
following solo functions are provided:

Pre-fader Listen (PFL)

After-fader Listen (AFL)

Solo-In-Place (SIP
Pre-fader Listen (PFL):

The Solo Bus is fed pre-fader from the channel or echo return

Non-destructive

Mono

Solo Level Control

After-fader Listen (AFL):

The Solo Bus is fed post-fader from the channel or echo return

Non-destructive

Mono

Solo Level Control

Solo-In-Place (SIP):

Destructive (all other channels/returns will mute when the SOLO button is engaged
in this mode)

The soloed channels/returns are monitored via the Program Bus

Panned

Post-fader
NOTE: PFL is the default solo mode.

38

NOTE: Channels and Echo Returns must be assigned to the Program Bus for Solo-InPlace for their mutes to activate when other channels or Echo Returns are
soloed.
NOTE: Sub-masters assigned to the Program Bus will mute if the console is in Solo-InPlace and a channel or Echo Return is soloed.
The 840B Solo Master controls function as follows:
SOLO SUM L and R CAL (trim-pot): Calibrates the level of the Left
and Right channel contributions to the PFL and AFL solo bus
LEVEL: Volume control for PFL and AFL solos
No Buttons Engaged: PFL is the active solo function
SIP (Solo-In-Place): Selects the Solo-In-Place solo function

Illuminates when engaged

AFL (After-Fader Listen): Selects the After-Fader Listen solo
function

Illuminates when engaged

CLEAR:

Disengages all engaged channel/echo return SOLO buttons

Provides a quick and easy method to turn off channel/echo return solos
Does not clear Echo Send or Summing Bus Master solos
Momentary switch
Illuminates as a flashing light when any solo mode is engaged

Note: If Solo Clear is pushed, and the button remains flashing, there is either an Echo Send
or a Summing Bus Master solo latched
7.6

Channel Meter Control

The 840B Channel Meter section selects the source for the sixteen Channel Meters in the Meter
Bridge. All sixteen Channel Meters can display the following sources:

Channel Preamp output

Channel Direct Output

The first eight Channel Meters can also display:

Summing Bus masters (SUB 1-8) output

The 840B Channel Meter controls function as follows:
No Buttons Engaged: Meters display the output of the channel
Preamps
DIR OUT (Direct Output): Meters display the output of the channel
Direct Output

Replaces the channel Preamp output meter feed

Illuminates in when engaged

SUB MSTR (Sub-master): Meters 1-8 display the output of the Summing Bus Sub-masters (SUB
1-8)

Replaces the channel Preamp output and Direct Output meter feeds for Meters 1-8

Meters 9-16 will display the channel Preamp output

Meters 9-16 will display the channel Direct Output if the DIR OUT button is engaged

Illuminates in when engaged

39

7.7

Peak Threshold
The 840B Peak Threshold section allows the selection of one of six Peak Thresholds. When the
signal in a channel crosses the selected threshold, the MIC button on that channel turns red,
indicating a peak has been reached. There is also a selector position and trim-pot for Peak
Indicator calibration.
The 840B Peak Threshold controls function as follows:
Peak
from

Threshold Selector: Selects the Peak Indicators threshold

the following choices:
+4dBU
+8dBU
+12dBU
+16dBU
+20dBU
+24dBU
CAL

CAL (trim-pot): Calibrates the Peak Indicator

CAL must be selected on the Peak Threshold selector

7.8

Oscillator
The 840B Oscillator section provides a full-range sine wave oscillator with the following
features:

Twelve frequency selections from 20Hz to 20kHz

On/off switch

Level control

Assignment to the Program and Summing Buses

Balanced, line-level output

The 840B Oscillator controls function as follows:
Frequency Selector: Selects the Oscillator frequency from the
following choices:

20Hz

50Hz

100Hz

300Hz

500Hz

1kHz

2kHz

3kHz

5kHz

8kHz

10kHz

20 kHz

LEVEL: Controls the output level of the Oscillator

ON: On/off switch for the Oscillator output

The Oscillator output is fed to the OSCILLATOR output connector on the rear panel

Illuminates in red when engaged

TO BUS: Routes Oscillator output to the Program and Summing Buses

The Left and Right Program Bus Output Masters must be turned ON with the level up to
enable the Oscillator to feed the Program Buses

The eight Summing Bus Sub-masters (SUB 1-8) must be turned ON with the level up to
enable Oscillator to feed the Summing Buses

Automatically engages the CR DIM function when engaged

Illuminates in red when engaged

40

7.9

840B Connections
The rear panel connections for the 840B Central Facilities module are as follows:

TALKBACK: Talkback Remote Port

Pin 1 = +5 volts (fused)

Pin 2 = T/B To Echo

Pin 3 = T/B to All

Pin 4 = T/B Slate

Pin 5 = Ground

5-Pin Female XLR connector

Connect pin5 to pin 2, 3, or 4 through

an external momentary switch for
remote talkback use
OSCILLATOR: Oscillator Output

Balanced, Line-level

Male XLR connector

NOTE: The screened pinout on the rear panel of the 1608 is

actually WRONG. The CORRECT pinout is as above.

7.10

STEREO HEADPHONE JACK

STEREO HEADPHONE JACK: (under armrest on Right side of console)

Headphone amplifier output

1/4" tip-ring-sleeve jack

41

8.0

Meter Bridge
The 1608 Meter Bridge provides illuminated VU Meter display for the following outputs:

Channel Preamp

Channel Direct Output

Summing Bus Sub-master Output

Left and Right Program Output

Echo Send Output

The Talkback Microphone and Power Supply Indicators are also mounted in the Meter Bridge.

8.1

Channel/Bus Meters
The controls for the Meter Bridge are located in the Channel Meter section on the 840B Central
Facilities module. These controls select the sources for the sixteen Channel Meters in the Meter
Bridge as follows:
No Buttons Engaged: Meters display the output
of the channel Preamps
DIR OUT (Direct Output): Meters display the
output of the channel Direct Output

Replaces the channel Preamp output

meter feed

8.2

Left and Right Program Meters

SUB MSTR (Sub-master): Meters 1-8 display

the output of the Summing Bus Masters (SUB
1-8)

Replaces the channel Preamp output

and Direct Output meter feeds for
Meters 1-8

Meters 9-16 will display the channel

Preamp output

Meters 9-16 will display the channel

Direct Output if the DIR OUT button is
engaged

The large LEFT and RIGHT Meters display the stereo Program Master Output (post the Master
Fader).

42

8.3

Echo Send/Return Meters

The E1 E8 Meters display the
output of the eight Echo/Auxiliary
Send Masters (post the Echo Send
Master).

8.4

Power Supply Voltage Indicators

Blue

LED indicators are provided for the five power supply voltages:
+16V
-16V
+24V
+5V
+48V

The Power Supply Voltage Indicators are located to the left of the E5 and
E7 meters.
8.5

Talkback Microphone
The built-in Talkback Microphone is located below the Power Supply Voltage Indicators.

43

9.0

Rear Panel
9.1

548B Channel Module Connections

The rear panel connections for the 548B Channel module are as follows:

DIRECT OUTPUT:

Balanced, Line-level

Male XLR

INSERT

RETURN (FADER INPUT):

Balanced, Line-level
1/4 tip-ring-sleeve switching jack
Replaces the EQ Out signal when a jack is inserted
and the INS button is engaged

INSERT

SEND (EQUALIZER OUT):

Balanced, Line-level
1/4 tip-ring-sleeve switching jack
The feed to the Insert Return (Fader Input) is
defeated when a jack is inserted

EQUALIZER INPUT:

Balanced, Line-level

1/4 tip-ring-sleeve switching jack

The Preamp Output signal is replaced with this signal

when a jack is inserted
PREAMP

OUTPUT:
Balanced, Line-level
1/4 tip-ring-sleeve jack
Half-normalled to feed the Equalizer Input

INSTRUMENT INPUT:

Unbalanced, High-impedance

Instrument-level

1/4 tip-sleeve switching jack

The Microphone Input signal is replaced with this

signal when a jack is inserted
MIC INPUT:

Balanced, Low-impedance

Microphone-level

Female XLR connector

LINE INPUT:

Balanced, Low-impedance

Line-level

Female XLR connector

44

9.2

E1608 Echo Send/Return Connections

The rear panel connections for the E1608 Echo Send/Return module are as follows:
9.2.1

Echo Sends

ECHO SENDS EXTERNAL INPUT 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve jack

ECHO SENDS OUTPUT 1-8:

Output of the Echo/Auxiliary Masters

Balanced, Line-level

Female 25-Pin Sub-D connector

9.2.2

Echo Returns

ECHO RETURNS AUX INPUT 1-8:

Balanced, Line-level

1/4 tip-ring-sleeve jack

ECHO RETURNS INPUT 1-8:

Balanced, Line-level

Female 25-Pin Sub-D connector

9.2.3

Echo Return 500 Slots

ECHO RETURNS 500 SLOTS IN 1-8:

Fed from the Reverb Return Input

connector

Balanced, Line-level

1/4 tip-ring-sleeve switching jack

The signal from the Reverb Return Input

connector is replaced with this signal
when a jack is inserted
ECHO RETURNS 500 SLOTS OUT 1-8:

Output of the 500 Slot Balanced, Linelevel

1/4 tip-ring-sleeve jack

Also normalled to feed the Echo Return

module input

45

9.3

168B Summing Bus Sub-master (ACA) Connections

The rear panel connections for the 168B Summing Bus Sub-master module are as follows:
PGM BUS MIX INPUT:

Feeds the inputs to the Program Bus

Assignment switches on the Summing Bus Submasters 1-8

Balanced, Line-level

1/4 tip-ring-sleeve jack

Replaces the Summing Bus output signal at the

Left and Right Program Assignment switches
when a jack is inserted
BUS OUTPUT 1-8 (ACA OUTPUT):

Output from the Summing Bus Sub-masters

SUB 1-8

Balanced, Line-level

Female 25-Pin Sub-D connector

9.4

268B Program Bus/Master Output Connections

The rear panel connections for the 268B Program Bus/Master Outputs are as follows:

PROGRAM BUS INSERT SEND (ACA OUTPUT):

Balanced, Line-level

1/4 tip-ring-sleeve jack

Half-normalled to Program Insert Return

PROGRAM BUS INSERT RETURN (FADER INPUT):

Balanced, Line-level

1/4 tip-ring-sleeve jack

Replaces the Program Insert Send signal when a

jack is inserted and the PRG INS button is
engaged
PROGRAM BUS OUTPUT LEFT and RIGHT:

Fed post the Stereo Master Fader

Balanced, Line-level

Male XLR

46

9.5

268B Control Room Monitor Output Connections

The rear panel connections for the 268B Monitor Outputs are as follows:

SMALL 2 CONTROL ROOM OUTPUTS LEFT and RIGHT:

Balanced, Line-level

Male XLR

SMALL 1 CONTROL ROOM OUTPUTS LEFT and RIGHT:

Balanced, Line-level

Male XLR

MAIN CONTROL ROOM

RIGHT:

Balanced, Line-level

Male XLR

OUTPUTS

LEFT,

CENTER,

MAIN CONTROL ROOM OUTPUTS LEFT SURROUND,

CENTER, RIGHT SURROUND:

Balanced, Line-level

Male XLR

9.6

845B 6-Track Playback Input Connections

The rear panel connections for the 845B Control Room Control Monitor module are as follows:
6 TRACK PLAYBACK 1 LEFT and RIGHT Input:

Balanced, Line-level

Female XLR connectors

Left and Right are paralleled with input with

Sub-D connector
6 TRACK PLAYBACK INPUTS 1, 2, and 3:

Left, Center, Right, Left Surround, Right

Surround, LFE

Balanced, Line-level

Female 25-Pin Sub-D connector

6 Track Playback 1 is paralleled with the Left

and Right XLR connectors

47

9.7

840B Ancillary Connections

The rear panel connections for the 840B Central Facilities module are as follows:
9.7.1

Talkback Remote Port and Oscillator Output

TALKBACK: Talkback Remote Port

Pin 1 = +5 volts (fused)

Pin 2 = T/B To Echo

Pin 3 = T/B to All

Pin 4 = T/B Slate

Pin 5 = Ground

5-Pin Female XLR connector

OSCILLATOR: Oscillator Output

Balanced, Line-level

Male XLR connector

NOTE: The screened pinout on the rear panel of very early

1608s is actually WRONG (serial numbers below 020). The
CORRECT pinout is as above.

9.7.2

Stereo Headphone Output

Stereo Headphone Jack: (under armrest on the Right side of the frame)

Headphone amplifier output

1/4" tip-ring-sleeve jack

48

9.8

Expander Port
The Expander Port is interfaced with a single 90-Pin male Elco connector.
The 1608 is equipped with an Expander Port
that allows the connection of a sixteenchannel API 1608 Expander. The Expander
Port allows for complete integration of all
major console functions:

Program Bus

Summing Bus

Auxiliary Bus

Mute Group

Solo Bus

Solo-In-Place

9.9

Power Supply Unit Connection

The Power Supply Unit connection is interfaced with a single multi-pin mil spec. connector.

1608 Weights and Dimensions

Width
37.6 inches

Height
17.9 inches

Depth
33.0 inches

Weight
228 Lbs.

16 Channel
Expander

25.6 inches

17.9 inches

33.0 inches

162 Lbs.

32 Channel Console

50 inches

17.9 inches

33.0 inches

390 Lbs.

Standard 16 channel
console

49

10.0 Application Guide

The API 1608 is a highly versatile audio production console and is at home with a wide variety of
applications including:

Multitrack Recording

Overdubbing

Mixing

Broadcasting

Post

Live Sound
API realizes the owners of the 1608 are professional users, so this section of the manual is designed to
provide quick and easy setups for basic applications.
Note:

These setups are intended to be a very basic Getting Started guide and should by no means
considered to be comprehensive.

10.1

Multitrack Recording
This setup uses the 1608 as an input path to a multitrack recorder or Digital Audio Workstation
(DAW):
1) Connect the audio sources to be recorded to the channel module inputs as needed
2) Select the appropriate channel input for the sources to be recorded (microphone,
instrument, or line)
3) Connect the following to the inputs of the recorder or DAW as desired:

Channel Direct Outputs

Summing Bus Sub-master Outputs (if multiple channels need to be summed before
the input to the recordermake assignments as needed)
o Odd/Even panning is available
4) The channel input level and polarity will be set by the Preamp
5) Use the onboard filter and EQ as needed

Additional signal processors (such as a compressor) may be patched into various

places in the channel audio path via the Insert and other connections on the rear
panel
6) Connect the Direct Outputs or the Summing Bus Outputs to the desired recorder or DAW
inputs

The Direct Output is always fed by the channel Fader

Make the necessary Summing Bus assignments if needed

7) The multitrack feed will be controlled by the channel Fader and Mute

If the Summing Buses are used, the Summing Bus Sub-masters (SUB 1-8) will
provide a final output control before the recorder or DAW
8) Unused channels and echo returns can be used to create a mix of the multitrack/DAW
returns

If a DAW is used, tracks could be sub-grouped as needed before feeding the DAW
outputs
9) The mix of the multitrack returns and cue/effects sends can be created in the box (using
the DAW mix and auxiliary buses and outputs)

If a DAW is not being used, unused 1608 channels and echo returns can be used to
create the needed mixes
10) If a stereo mix is created in the DAW, it could be routed back to the console via unused
channels, echo returns, an external control room monitor input, or even the Program Bus
insert return for further processing, routing, and/or monitoring

50

Multitrack Recording Scenario #1

The diagram below shows the connections between a 1608 and a Digital Audio Workstation
(DAW) with 24 line inputs. The first 16 channels feed the DAW inputs 1-16 via the Channel
Direct Outputs. DAW inputs 17-24 are fed from the 1608 Summing Bus Outputs 1-8, providing
versatile assignment possibilities.
If the Echo Return 500 slots are fitted with 512C
Preamplifiers or outboard preamps are fed to the Echo Return inputs, the 1608 can provide 24
independent input channels and output paths to a DAW (or other multitrack recorder).

This scenario requires the engineer to sum the recorded channels to a mix within the DAW and
output this mix for monitoring. The diagram below this mix returns to the Program Bus Mix
Inputs. The signal from these jacks is routed to the 1608 Program Bus by assigning the
corresponding Summing Bus Masters to the Left and Right Program Bus on the 168B module.
This allows the DAW mix to feed the Program Bus Inserts and Master Fader.

NOTE: This scenario requires the use of a pair of Summing Bus Masters to return the stereo mix
to the Program Bus. If used for this purpose, the selected Summing Buses cannot be used as
multitrack sends.

51

Multitrack Recording Scenario #2

The diagram below shows the connections as above, except the mix return from the DAW is
routed directly to the 845B Control Room Monitor module for monitoring. In this scenario, the
Program Bus Inserts and Master Fader are bypassed.
This scenario requires the engineer to sum the recorded channels to a stereo or 5.1 mix within
the DAW and output this mix for monitoring via the 845B Control Room Monitor module.

52

10.2

Multichannel Mixing
This setup uses the 1608 as a return path and mixer from a multitrack recorder, DAW, stage, or
other sources. It can be used while tracking, overdubbing, and mixing. If used during tracking
or overdubbing, the input to the recorder or DAW might be fed by unused 1608 channels/echo
returns or an audio path thats external to the console.
1) Connect the returns (outputs) from the recorder, DAW, or other sources to the channel Line
Inputs as desired

If a DAW is used, tracks could be sub-grouped as needed before feeding the DAW
2) Additional mix inputs can be created using:

Echo Returns (see below)

Echo Send External Input (see below)

Program Bus Mix Inputs (see below)

3) Select Line Input on the channels connected to multitrack returns (the Line Input is the
default channel input, so no buttons need to be engaged)
4) Engage the PGM buttons to assign the channels (and other inputs) to the Left and Right
Program Buses (stereo mix buses)
5) The Summing Buses and/or Echo/Aux sends can be used to create the additional mix
outputs needed for multichannel mixing (LCRS, 5.1, 5.1EX, 7.1)
6) Use the onboard filter and EQ as needed

Additional signal processors (such as a compressor) may be patched into various

places in the channel audio path via the Insert and other connections on the rear
panel
7) The contribution to the mix will be controlled by the channel Fader, Mute, and Pan-pot
8) The channel Echo Sends and Auxiliary Buses can be used for:

Echo sends to feed effects units

Pre-fader cue/foldback sends (for tracking, overdubbing, broadcasting, live events)

Sub-group sends

Additional output paths for multichannel mixing (LCRS, 5.1, 5.1EX, 7.1)
9) Summing Buses can also be used as:

Multitrack summing

Additional post-fader mono auxiliary sends

Audio sub-groups sends

Additional mix outputs

Additional output paths for multichannel mixing (LCRS, 5.1, 5.1EX, 7.1)
10) Summing Buses Output Sub-masters can be used as:

Multitrack output masters

Additional post-fader mono auxiliary send masters

Audio sub-groups masters

Additional mix inputs

Additional mix output masters

Output masters for multichannel mixing (LCRS, 5.1, 5.1EX, 7.1)

11) Echo Send modules can be used as:

Echo/Auxiliary Bus Masters for feeds to effects units and cue/foldback systems

Additional mix inputs

Sub-group masters

Additional output paths for multichannel mixing (LCRS, 5.1, 5.1EX, 7.1)
12) Echo Returns can be used as:

Echo Returns for effects units and other devices

Additional mix inputs

Input channels for tracking and overdubbing

Sub-group mix returns

13) Unused channels can be used as:

Additional mix inputs

Input channels for tracking and overdubbing

Echo Returns for effects units and other devices

Sub-group returns (patching required)

14) The Program Bus Inserts can be used for additional processing of the Left and Right mix
(such as equalization and/or compression)
15) The contribution to Left and Right Program outputs will be controlled by the channel Left
and Right Program Output Masters (PGM L and R) and the Stereo Master Fader
16) Connect the Left and Right Program outputs (and other outputs if multichannel mixing) to
the mix recorder inputs

53

17) The mix of the multitrack returns could be routed back to the console via channels, echo
returns, an external control room monitor input, or even the Program Bus insert return for
further processing, routing, and/or monitoring
Mixing Scenarios
The diagram below shows the connections between a Digital Audio Workstation (DAW) with 24
line outputs and a 1608 for stereo or surround mixing. The first 16 channels are fed from the
DAW outputs 1-16 via the Channel Line Inputs. DAW outputs 17-24 are fed to the 1608 Echo
Return Inputs 1-8.

Select the Line input on channels.

For stereo mixing make assignments to the Program Bus.
For surround mixing, use Program and Summing Bus 1-4 assignments to create six mix paths
for 5.1 mixing as follows:
Left
Right
Center
Sub (LFE)
Left Surround
Right Surround

Program Bus Left

Program Bus Right
Summing Bus 1
Summing Bus 2
Summing Bus 3
Summing Bus 4

Make Program and Summing Bus assignments as need to route the channels to the appropriate
mix bus(es).
Turn ON Aux Sends 7 and 8 and engage the TO BUS button. This will allow Aux Sends 7 and 8
to act as level, mute, and pan controls for contributions to the mix via Summing Buses 1-4

54

(Center, Sub, Ls, Rs). When the PRE button is engaged, Aux Sends 7 and 8 are fed pre-fader.
This provides independent control when a channel is also assigned to the Program Bus.
The Echo Returns can be used to return additional channels from the DAW, returns from virtual
instruments, returns from outboard effects processors, or any other line-level source. If the
Echo Return 500 slots are fitted with the 550A Discrete 3-Band EQ, 550B 4-Band EQ, 560
Graphic EQ and/or 525 Compressors, the audio returning to the Echo Returns can be further
processed before contributing to the mix.
Echo Returns are assigned to contribute to the mix in the same manner as with the channels for
both stereo and surround mixing. Engage the PAN button to enable the pan-pot.
Outboard Effects Processor Connections
The diagram below shows the connections between a 1608 and outboard effects processors for
either mixing scenario above. Returning the outputs of the outboard effects processors to the
Echo Returns Auxiliary Inputs allows easy switching of the Echo Return input source between
the return of the DAW (main input) and the return from the effects processor (Aux Input)
without changing connections on the rear panel.

55

Mix Output Connections

The diagram below shows mix output connected to a DAW (or other mix recorder).

56

Basic Record and Mix Connections

The diagram below shows the connections between a 1608 and a DAW (or other multitrack
recorded) for both recording and mixing without changing connections on the rear panel.
For recording, select the Mic or Instrument input on the 1608 channels and output to the DAW
via the Channel Direct Output or Summing Bus assignments. The Echo Returns can be used as
addition input channels as needed, feeding the DAW via assignments to the Summing Buses.
During recording, a stereo mix can be created in the DAW and monitored as described in the
Multitrack Recording scenarios above.
For mixing, select the Line input on the channels and assign them to the Program Bus for stereo
mixing and the Program Bus and/or Summing Buses for surround mixing. The Echo Returns
can be assigned accordingly and used to return additional channels from the DAW or returns
from outboard effects processors.

10.3

DAW Hybrid
It is possible to use the 1608 as both the input path to a multitrack recorder or DAW and a
return path for mixing as well. This is accomplished by interfacing the recorder or DAW within
the channel signal flow. This simultaneously provides high-quality input paths for recording and
powerful analog mixing capabilities. It is best suited for use with a DAW, but could be used
with any multitrack recorder. Possible configurations include:
Preamp Output to DAW Input DAW Output to Equalizer Input:

Input Path: Preamp Only

Return Path: EQ, Insert, Fader, Filter, Panning, Output Assignments, Echo/Aux Sends
Insert Send (EQ Output) to DAW Input DAW Output to Insert Return (Fader Input):

Input Path: Preamp and EQ

Return Path: Fader, Filter, Panning, Output Assignments, Echo/Aux Sends

Additional signal processing can be added at any point in the patching if needed.
Another possible configuration is using the 1608 channels to feed the multitrack recorder or
DAW and the Echo Returns as multitrack returns (or vice-versa). This might require subgrouping the tracks before feeding the DAW outputs.

57

10.4

E1608 Echo Send Applications

Echo Send Master:

Turn the Echo Send ON

Set the level to unity gain

The Echo Send is fed by the corresponding Auxiliary Bus

The Echo Send output is fed to the Echo Sends Output connector
Mix Input:

Connect the output of the desired device (effects unit, recorder, DAW, etc.) to the Echo
Send External Input

Engage the EXT IN

Turn the Echo Send ON

Set the Echo Send level to unity gain

The Echo Send is fed by the External Input and the corresponding Auxiliary Bus
o Do not use the corresponding channel Echo sends if an isolated input is desired

Press the MIX button on the corresponding Echo Return

The Echo Send output is fed to the Echo Return and the Echo Sends Output connector

Assign the Echo Return to the Program Bus and/or Summing Buses as needed

Engage the PAN button if panning is needed

Set the Echo Return level as desired

Audio Sub-group Master:

Use channel Echo sends to feed the channels to be grouped to the desired Auxiliary
Buses
o It might be desirable to de-assign these channels from the Program Bus

Turn the Echo Send ON

Set the Echo Send level to unity gain

The Echo Send is fed by the corresponding Auxiliary Bus

Press the MIX button on the corresponding Echo Return

The Echo Send output is fed to the Echo Return and the Echo Sends Output connector

Assign the Echo Return to the Program Bus and/or Summing Buses as needed

Engage the PAN button if panning is needed

Set the Echo Return level as desired

Aux Send Multichannel Mix Output Master (LCRS, 5.1, 5.1EX, 7.1):

Use the Program Bus for the Left and Right channels

Select four channel Echo/Aux Sends for use as Center, Left Surround, Right Surround,
and LFE channels
o Using a stereo aux send for the Left and Right Surround channels is suggested
o Using a mono aux send for the Center and LFE channels is suggested

Make sure the PRE buttons are not engaged if you want the send to follow the Fader

Turn the selected channel Aux Sends ON and set the levels to unity gain or as needed

Use the channel fader to adjust the contribution to the assigned 5.1 mix channels

Turn ON the selected Echo Send modules

Set the Echo Send level to unity gain

The Echo Send module is fed by the corresponding Auxiliary Bus

The L/R mix outputs are fed to the L/R Program Output connectors

The Ls, Rs, C, and LFE mix outputs are fed to the Echo Sends Output connector

Use addition Aux Sends if additional mix outputs are needed

58

10.5

E1608 Echo Return Applications

Echo Return/Mix Input:

Connect the output of the desired device (effects unit, recorder, DAW, etc.) to the Echo
Return Input or Echo Return Auxiliary Input

Engage the AUX IN button if desired

Assign to the Program Bus

Engage PAN button to engage the Pan-pot if needed

Set the level and pan as desired

Tracking Input:

Connect the output of an external preamp or other line-level device to the Echo Return
Input or Echo Return Auxiliary Input
o If an API 512C Preamp is mounted in the corresponding Echo Return 500 Slot, it
can be used as a microphone or instrument preamp

Engage the AUX IN button if desired

Assign to the desired Summing Bus(es)

Engage PAN button to engage the Pan-pot if Odd/Even panning is needed

The Echo Return level will control the output to the Summing Bus

The Summing Bus feeds Summing Bus Sub-master (SUB 1-8)

Turn ON the corresponding Sub-master

Set the sub-master to unity gain or as needed

Connect the Bus Output connector to the input to the recorder or DAW
Audio Sub-group Return:

Use channel Echo/Aux sends to feed the channels to be grouped to the desired Auxiliary
Buses
o It might be desirable to de-assign these channels from the Program Bus

Turn the Echo Send ON

Set the Echo Send level to unity gain

The Echo Send is fed by the corresponding Auxiliary Bus

Press the MIX button on the corresponding Echo Return

The Echo Send output is fed to the Echo Return and the Echo Sends Output connector

Assign the Echo Return to the Program Bus and/or Summing Buses as needed

Engage the PAN button if panning is needed

Set the Echo Return level as desired

NOTE: Alternately the outputs from the Summing Bus Sub-masters may be patched to
the Echo Return Inputs (or Aux Inputs) to feed a sub-group to the Echo Returns.

59

10.6

168B Summing Bus Sub-master Applications

Multitrack and Audio Sub-group Master:

Use channel assignment buttons to feed the post-fader signal to the desired Summing
Bus(es)

The audio from all of the channels contributing to a summing bus will be summed at the
Sub-master

Turn ON the corresponding Summing Bus Sub-master

Set the level to unity gain or as needed

The sub-master output is fed by the corresponding Bus Output connector

Connect the Bus Output to the input of the recorder, DAW, or unused input (patching
required)
Echo Send Master:

Use channel assignment buttons to feed the post-fader signal to the desired Summing
Bus(es)

Turn ON the corresponding Summing Bus Sub-master

Set the level to unity gain

The Sub-master output is fed by the corresponding Bus Output connector

Connect the Bus Output to the input of the device to be used

Mix Input:

Connect the output of the desired device (effects unit, recorder, DAW, etc.) to the
Program Bus Mix Input

This input feeds the input to the Program Bus Assignment switches on the Summing Bus
Sub-masters 1-8

Turn the corresponding Sub-master ON

Assign to the Program Bus

Use the TRIM control to set the desired level

Summing Bus Multichannel Mix Outputs (LCRS, 5.1, 5.1EX, 7.1):

Use the Program Bus for the Left and Right channels

Select four Summing Buses for use as Center, Left Surround, Right Surround, and LFE
channels and make the appropriate assignments
o The Pan-pot may be engaged for Left and Right Surround panning

Use the channel fader to adjust the contribution to the assigned 5.1 mix channels

Turn ON the selected Summing Bus Sub-masters (SUM 1-8)

Set the levels to unity gain

The Summing Bus Sub-masters are fed by the corresponding Summing Buses

The L/R mix outputs are fed to the L/R Program Output connectors

The Ls, Rs, C, and LFE mix outputs are fed to the Buss Output connector

Use addition Summing Buses if additional mix outputs are needed

The Summing Buses and Sub-masters can also be used as additional Left and Right mix
outputs

60

10.7

Echo Return 500 Slot Applications

The console is equipped with eight Echo Return 500 Slots. These 500 Slots are built to power
and interface any API 500 Series module:

512C Preamplifier

525 Compressor

550A 3-Band EQ

550B 4-Band EQ

560 Graphic EQ
Some possible applications of the 500 Slots include:

Extra microphone/instrument inputs (when equipped with a 512C Preamp)

Extra signal processing for the Echo Return inputs

Patchable signal processing for use in the channel Inserts and patch points

Patchable signal processing for use in the Program Bus Inserts

Patchable signal processing for use anywhere else (internally, externally, etc.)
When equipped with a 512C Preamp, the 500 Slot and Echo Return combine to form a powerful
input module capable of routing a microphone, instrument, or line input to the Program and/or
Summing Buses with full assignment, panning, and solo functions. This can greatly expand the
capabilities of the console for almost all applications.
When equipped with a 512C Preamp, an API EQ, and a 525 Compressor, three 500 Slots can be
used to create a single high-quality signal path for direct feed to the multitrack recorder or
DAW.
As indicated by these examples, the 500 Slots can be custom configured to add versatility and
maximize performance.
The features of the 500 Slots are as follows:

All eight 500 Slots are empty in the standard 1608 configuration. If a slot is empty, the
signal will loop through the slot to feed the corresponding Echo Return input when a
Bypass Card is inserted into the card edge connector of the corresponding slot (These
cards are supplied by API when the console is delivered without 500 modules in any 500
slot)

500 Slots can deliver 48v phantom power to the Echo Return Input connector if
equipped with a 512C Preamp

The slots are normalled between the Echo Returns Input connector and the inputs to the
Echo Return modules

If engaged, the module mounted in a slot will process the audio before it arrives at the
Echo Return module input

If a slot is empty, the signal will loop through the slot to feed the corresponding Echo
Return module input

The modules in the Echo Return 500 Slots may be used elsewhere by using the ECHO
RETURN 500 SLOT INPUT and OUTPUT patch points on the rear panel

Inserting a plug into the ECHO RETURN 500 SLOT INPUT jack will defeat the signal from
the Echo Return Input connector, but the output of the slot is still sent to the Echo
Return module

The 500 Slot may be bypassed by using the Echo Return Auxiliary Input

WARNING WARNING WARNING WARNING WARNING

The use of NON-VPR Alliance approved 500 series modules in the 1608 is vehemently
discouraged, and may cause operational difficulties with the console. Improper
operation, excessive current draw and poor module fit are all potential issues with
these devices.
For the most recent
www.apiaudio.com.

list

of

VPR

Alliance

approved

modules,

please

visit

API reserves the right to deny warranty claims when non-VPR Alliance 500 series
modules are used.

61

10.8

Rear Panel DB25 Wiring Diagrams

The Rear panel DB25 connectors of the 1608 are wired as follows;

62

API 1608 Limited Warranty

a.

Warranty Information: This product carries a one year labor and a five year parts warranty from date of purchase. API
(Automated Processes, Incorporated) does not cover claims for damage due to alteration and/or abuse. This warranty is
limited to failures during normal use, which are due to defects in material or workmanship. If any defects are found in the
materials or workmanship, or if the product fails to function properly during the applicable warranty period, API, at its
option, will repair or replace the product.

b.

PLEASE NOTE: The design or quality of any non-authorized third party service or vendor is beyond the control of API.
Therefore, use of NON-API VPR Alliance modules in any API product including consoles may VOID this warranty.
Also, service or modification of any API unit except by an authorized API representative may VOID this warranty.

c.

API reserves the right to inspect any products that may be the subject of any warranty claims before repair or replacement is
carried out. Final determination of warranty coverage lies solely with API.

d.

This warranty is extended to the original purchaser and to anyone who may subsequently purchase this product within the
applicable warranty period. Proof of purchase may be required.

e.

To obtain service:
a.

Call API at 301-776-7879, 8:30 AM to 5 PM Monday through Friday (Eastern Time) to get a Return Authorization (RA).
Products returned without an RA number may not be accepted.

b.

Pack the defective part by wrapping in plastic and cushioning material. Seal securely in an approved shipping container.
If you do not have a sufficient shipping container, ask API for advice when calling for the RA number.

c.

Include a note explaining the problem and conditions of the service request. Include your complete return address (no
P.O. Boxes, please)

d.

Ship the product freight prepaid to:

API
8301 Patuxent Range Road
Jessup, MD 20794

IMPORTANT: Be sure the RA number is plainly written on the shipping carton

f.

This is your sole warranty. API does not authorize any third party, including any dealer or sales representative, to assume
liability on behalf of API or to make any warranty for API.

g.

THE WARRANTY GIVEN ON THIS PAGE IS THE SOLE WARRANTY GIVEN BY API AND IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS AND IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE. THE WARRANTY GIVEN ON THIS PAGE SHALL BE STRICTLY
LIMITED IN DURATION TO FIVE (5) YEARS FROM THE DATE OF THE ORIGINAL PURCHASE FROM API OR AN
AUTHORIZED API DEALER. UPON EXPIRATION OF THE APPLICABLE WARRANTY PERIOD API SHALL HAVE
NO FURTHER WARRANTY OBLIGATION OF ANY KIND. API SHALL NOT BE LIABLE FOR ANY INCIDENTAL,
SPECIAL, OR CONSEQUENTIAL DAMAGES THAT MAY RESULT FROM ANY DEFECT IN THE API PRODUCT OR
ANY WARRANTY CLAIM.

h.

This warranty provides specific legal rights and you may have other rights which vary from state to state.

63

Housekeeping:
This is a great place to write down the serial number of your
1608 console and your purchase information, just in case you
need that information someday in the future.

1608 serial Number: ________________________

Power Supply serial Number: __________________

Purchase Date: ______/________/________

64

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A P I , 8 3 0 1 P a t u x e n t R a n g e
T e l: 3 0 1 - 7 7 6 - 7 8 7 9

R o a d , J e s s u p , M D
2 0 7 9 4
w w w .a p ia u d io .c o m

In a c o n s ta n t e ffo r t to im p r o v e th e s u b tle d e ta ils o f o u r p r o d u c ts , s o m e a m o u n t o f c h a n g e is in e v ita b le .

A P I r e s e r v e s th e r ig h t to m o d ify o r c h a n g e a n y o f th e fe a tu r e s , s p e c ific a tio n s o r p e r fo r m a n c e o f its p r o d u c ts w ith o u t n o tic e o r o b lig a tio n .