Moodring 2017
FX Type: Reverb
© 2017 madbeanpedals
2.3” W x 2.95” H
Terms of Use: You are free to use purchased circuit boards for both DIY and small commercial operations. You may not offer these PCBs for resale or
as part of a “kit” in a commercial fashion. Peer to peer re-sale is, of course, okay.
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B.O.M.
Resistors Caps Diodes
R1 1M C1 100n D1 1N5817
R2 470k C2 10pF D2 Yellow
R3 1M C3 100pF D3, D4 Red
R4 10k C4 1uF Transistors
R5 10k C5 1uF Q1 J201
R6 470R C6 6n8 Regulators
R7 100k C7 330pF REG1 LM78L05
R8 10k C8 47n REG2 LM78L05
R9 1M C9 1uF ICs
R10 10k C10 1n IC1 TL072
R11 10k C11 1n IC2 BTDR-2
R12 10k C12 100n IC3 PT2399
R13 10k C13 100n IC4 TL072
R14 10k C14 15n Switch
R15 20k C15 10n DRY SPDT
R16 10k C16 1uF Trimmers
R17 10k C17 10uF VOL 50k
R18 20k C18 100n GAIN 25k
R19 1k5 C19 1uF Pots
R20 33k C20 10n SPACE 25kB
R21 100k C21 15n DWELL 100kB
R22 100k C22 1uF MOOD 100kB
R23 1k C23 1uF RING 100kB
R24 1k C24 100pF
R25 47k C25 1uF
R26 22k C26 10n
R27 1M C27 220n
R28 2k4 C28 1uF
R29 3k3 C29 10uF
R30 1k C30 100n
R31 4k7 C31 47uF
R32 10k C32 100n
R34 4k7 C33 100n
R35 10k C34 100uF
R36 10k C35 100n
R37 1k5 C36 10uF
*note – There is no R33 on this board
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Shopping List
Value QTY Type Rating
470R 1 Carbon / Metal Film 1/4W
1k 3 Carbon / Metal Film 1/4W
1k5 2 Carbon / Metal Film 1/4W
2k4 1 Carbon / Metal Film 1/4W
3k3 1 Carbon / Metal Film 1/4W
4k7 2 Carbon / Metal Film 1/4W
10k 13 Carbon / Metal Film 1/4W
20k 2 Carbon / Metal Film 1/4W
22k 1 Carbon / Metal Film 1/4W
33k 1 Carbon / Metal Film 1/4W
47k 1 Carbon / Metal Film 1/4W
100k 3 Carbon / Metal Film 1/4W
470k 1 Carbon / Metal Film 1/4W
1M 4 Carbon / Metal Film 1/4W
10pF 1 Ceramic / MLCC ~16v min
100pF 2 Ceramic / MLCC ~16v min
330pF 1 Ceramic / MLCC ~16v min
1n 2 Film ~16v min
6n8 1 Film ~16v min
10n 3 Film ~16v min
15n 2 Film ~16v min
47n 1 Film ~16v min
100n 8 Film ~16v min
220n 1 Film ~16v min
1uF 1 Film ~16v min
1uF 8 Electrolytic ~16v min
10uF 3 Electrolytic ~16v min
47uF 1 Electrolytic ~16v min
100uF 1 Electrolytic ~16v min
1N5817 1
Yellow 1 Diffused 5mm
Red 2 Diffused 5mm
J201 1 or, 2n5457, MPF102
LM78L05 2
TL072 2
BTDR-2 1 *see notes
PT2399 1
SPDT 1 Mini Switch
50k 1 Bourns 3362p
25k 1 Bourns 3362p
25kB 1 PCB Right Angle 16mm
100kB 3 PCB Right Angle 16mm
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BTDR-2H:
https://www.mammothelectronics.com/products/accubell-sound-belton-btdr-2h-digital-reverb-module-
horizontal?variant=31876478791
http://www.smallbear-electronics.mybigcommerce.com/belton-btdr-2h-reverb-modules/
(smallbear appears to be out of stock of these at this time)
http://www.pedalpartsplus.com/product-p/14000.htm
https://www.banzaimusic.com/Belton-Reverbs/
https://www.musikding.de/Delay-Reverb_1
You can also find them on Reverb and eBay
Note: There are three versions of the BTDR-2H; the short, medium and long. I used the short version in my 2017 build
and it’s what I prefer. I find that the short version still has tons of reverb on tap and seems to have a bit less of the built-in
modulation (common in the Belton bricks).
Sub-Mini SPDT:
http://www.smallbear-electronics.mybigcommerce.com/spdt-on-on-mountain-10tc410/
The sub-mini switch is preferred in this build but if you cannot get it use a regular size (solder lug) SPDT. You may need
to make a small adjustment to the drilling layout in order to fit a larger switch.
Bourns 3362p:
25k:
https://www.mouser.com/productdetail/bourns/3362p-1-
253lf?qs=sGAEpiMZZMvygUB3GLcD7vRbQqL9uMLMqIpepdvyyRc%3D
20k (fine for 25k sub):
http://www.taydaelectronics.com/potentiometer-variable-resistors/cermet-potentiometers/3362p/20k-ohm-trimmer-
potentiometer-cermet-1-turn-3362p.html
50k:
https://www.mouser.com/productdetail/bourns/3362p-1-
503lf?qs=sGAEpiMZZMvygUB3GLcD7vRbQqL9uMLMZgtO2Ks3Q%2F4%3D
http://www.taydaelectronics.com/potentiometer-variable-resistors/cermet-potentiometers/3362p/50k-ohm-trimmer-
potentiometer-cermet-1-turn-3362p.html’
Other part notes:
-2k4 is a less common value of resistor for many builders. Use 2k2 if you don’t have a 2k4.
-The yellow and two red LEDs must be diffused, but can be either 3mm or 5mm. These are not bypass/indicator LEDs.
They are to control clipping in the circuit.
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125B Drill Guide
5.52” W x 7.65” H
I use “Lumberg” style jacks on my builds, but Switchcraft style should also work fine.
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Wiring Guide
Bypass LED can be soldered directly to the PCB.
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2017 notes
I decided to discontinue the Moodring about a year ago thinking that I would only offer a more “deluxe” version of it using
the BTDR-3 module. However, over the course of 2017 so many people asked me about spare boards that it seemed like
I jumped the gun in cancelling it. So, the Moodring has been brought back. As with most projects, I can’t help but tinker
with them and I have added in some small, but very useful, improvements to the design.
The following changes were made:
1. Added output volume trimmer.
2. Switched from one LM7805 regulator to two LM78L05 regulators (one for the BTDR and one for the PT2399).
3. Added a JFET buffer in the Dwell path (IMO, this ended up making a pretty big difference in the amount of
regeneration on tap and gave it a more “ethereal” quality at high settings.)
4. Switched D2 from red to yellow. This is fairly subtle but the change of LED color seems to clip the PT2399 output
slightly less and overall made the effect sound better to me.
5. Removed the “tails” bypass. This was a consequence of the added buffer in the Dwell control. High settings of the
Dwell leads to lots of feedback and self/oscillation which will not work with a tails bypass.
6. A few other small value tweaks.
Controls
RING: The amount of reverb mixed with the dry signal.
MOOD: A tone control for the reverb.
SPACE: The amount of pre-delay before the reverb. This goes from a few ms to about 300ms.
DWELL: The amount of reverb fed back into the pre-delay/reverb section.
DRY: This switch lets you kill the dry signal so that you only have reverb going to the output.
T1: This is an adjustable gain stage. Stock setting is about ¼ up. As you turn it up further, the reverb gets louder. This will
let you fine tune just how much reverb gets fed into the RING and DWELL knobs.
VOL: This “set and forget” trimmer is used to match the effect output with the bypass signal.
Design Breakdown
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Circuit (pseudo) Analysis
Input Stage/Output Mixer: Inverted method with high input impedance low output impedance. The
implementation results in a fairly flat frequency response and minimal volume change to the inputted
signal.
Filtering: Active filtering was chosen for the pre-emphasis portion of the reverb for convenience.
Pre-Delay: The PT2399 offers an adjustable pre-delay into the reverb section. Filtering here was kept
to a minimum. The pre-delay circuit ranges from a few ms to about 300ms.
Clipping: LED clippers were used before the reverb circuit to limit excessive volume and noise from
over-saturating its input. The higher forward voltage means they only begin to clip when the Dwell
control is near maximum.
Reverb: The BTDR-2 was used here for availability, ease of use and size.
Tone: A Big Muff™ style tone control offered the best range of filter shaping on the reverb.
Gain Recovery: With the tone control, signal loss was a concern. Luckily, we have one-half of an op-
amp left over to make a simple adjustable gain recovery stage.
Feedback: Feeding the output back into the reverb proved to offer some unique settings. It helps
increase ambience and grit. It can even create drone-like settings. The Dwell and Tone control are
somewhat interactive in this respect.
Dry Kill: A simple switch to remove the dry signal turns out to be a great option. Volume swells and
light dynamics really shine.
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Notes
The BTDR-2 is the only Belton Brick that will work with this design. The BTDR-1 and 3 are not
compatible with the PCB.
The BTDR-2 has modulation built into its design, for better or worse. It cannot be “turned off” (unless
you want to disassemble the module and remove a surface mount part). From what I can tell, it
seems to be a triangle wave with a period of about a second…maybe a little more. The modulation
did not seem to pose any problems in the Moodring. 2017 note: as I mentioned before I think the
intrinsic modulation is a little less pronounced in the “short” version of the brick, which I liked in my
2017 build.
The module itself should be soldered on the bottom side of the board with the pots. It must be
soldered in the correct way to work. Pin1 is the square pin of IC2 (the BTDR-2). Since there are parts
on the top part of the PCB in that area, make doubly sure that you have used the right values,
soldered them well, etc. It will be very difficult to remove the BTDR module once it is soldered in place
(unless you have a de-soldering gun).
IMPROTANT: the module is rather thick and runs the risk of being almost (but not quite) too tall for
the PCB mounted pots. Keep your component leads trimmed close to the pads that are underneath
the module and push the pins as far through the PCB pads as you can to avoid any problem with the
module thickness.
Voltages
IC1 IC2 IC3
1 4.54 1 5.02 1 5.02
2 4.54 2 1.7mV 2 2.53
3 4.54 3 ignore 3 0
4 0 4 0 4 0
5 4.54 5 1.8mV 5 2.84
6 4.54 6 1.8mV 6 2.53
7 4.54 7 0.69
8 9.08 8 0.71
9 2.53
IC4 Q1 10 2.53
1 4.54 D 9.08 11 2.53
2 4.54 S 0.47 12 2.53
3 4.13 G 1.4mV 13 2.53
4 0 14 2.54
5 4.13 15 2.53
6 4.54 16 2.53
7 4.54
8 9.08
9.42v One Spot supply
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Build Pic
Note: I used Function F(x) soft-touch bypass switching in this build, which is not something that is available for purchase.
youTube Demo:
https://www.youtube.com/watch?v=GhXyDXNpvH4
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