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Power corrupts. Class AB not as good. Hardly!

174.51.208.68
Posted on October 21, 2013 at 19:54:51
AbeCollins
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  Since: February 2, 2002
 My last attempt with a pair of 300wpc high powered solid-state mono amps was frustrating. I tried 'fixing' the dry, clinical, and sterile sound with a nice warm tube preamp in front of them but that was an uphill battle that I finally gave up on. The tube preamp helped a lot, but I was putting way too much effort into making the system sound right and finally sold those mono amps.

Since then I've been happily running my Rogue Cronus Magnum integrated (with KT120 tubes) for over a year and a half now and have been gun shy at trying solid-state amps again.

Of course I got the bug and another pair of solid-state mono amps have made their way into my system - again. I picked up a pair of one year old 300wpc Ampzilla 2000 2nd Edition mono amps by Spread Spectrum Technologies.

These things are actually built and serviced by the folks at Wyred 4 Sound but they're not Class D. They're traditional Class AB amps that weight just over 50 Lbs each and run barely warm to the touch. Of course spreading the heat across those large heat sinks probably help too.

In any case, since I don't have a preamp, I'm running my Accuphase DP-65V CD player into the amps via XLR balanced interconnects and using the CD player's remote volume control. It's very transparent and pretty neutral as best I can tell, which is to be expected I suppose since there's no preamp, nothing, between the CDP and amp. But what surprised me is that these Ampzillas are not at all clinical or dry. In fact there's no grain at all, a slight bit of sweetness, deep tight bass, with large soundstage and ease to them like there's a ton of head room left.

The setup isn't ideal with just the CDP but already I can tell that I like these solid-state monos much more than the previous pair I had experimented with.

Ampzilla 2000 2nd Edition, 1 of 2


Accuphase DP-65V CDP. An older but very good CDP






 

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I have very fond memories, posted on October 21, 2013 at 20:38:58
mbnx01
Audiophile

Posts: 7979
Location: Eagle, Idaho
Joined: October 22, 2004
 Of the original Ampzilla and other products from G.A.S. back in the day.

Glad to hear this version is holding up the family name.



'A lie is halfway around the world before the truth gets its boots on'. -Mark Twain

 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 21, 2013 at 21:11:52
John Elison
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Posts: 24056
Location: Central Kentucky
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  Since: January 29, 2004
 I have never owned a tube power amp, but I suspect they must sound very different than solid state voltage amplifiers. The reason is obvious. Tube amplifiers have output transformers that match their output impedance to the speakers' load impedance. As a result, their output voltage will vary all over the place as the impedance curve of the speaker varies all over the place. Solid State amplifiers are basically voltage amplifiers due to their extremely low output impedance.

I own a Parasound Halo A21 voltage amplifier with a damping factor of 1100. That means its output impedance equals 8-ohms ÷ 1100 = 0.0073-ohms. It is basically a voltage source. I connected a two channel AC Millivoltmeter to my speakers' terminals and played a 20-Hz to 20-kHz sweep from a test CD. The meter needles remained rock solid throughout the entire sweep. Try that with a tube power amplifier. I suspect the meter needles will rise and fall in concert with the speakers' impedance. That would definitely create a much different sounding presentation.

Best regards,
John Elison

 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 21, 2013 at 21:51:25
Trouser Trout
Audiophile

Posts: 286
Location: New England
Joined: August 25, 2010
 You should try the preamp outs of the Rogue to the Ampzilla's.

FF

 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 22, 2013 at 06:36:09
AbeCollins
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Posts: 49475
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Contributor
  Since: February 2, 2002
 Can I run the Rogue integrated w/o speakers attached to it? I would have to do that in order to run it's preamp outputs to the solid-state amps.



 

Thanks for explaining the benefits of tube amps., posted on October 22, 2013 at 07:24:25
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Do you really believe that low output impedance "is better than" having an OPT to match the load?

 

RE: Thanks for explaining the benefits of tube amps., posted on October 22, 2013 at 07:48:25
John Elison
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Posts: 24056
Location: Central Kentucky
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  Since: January 29, 2004
 If you want a flat frequency response from a speaker, then you need a flat voltage response from your amplifier. Speakers are designed to respond to constant voltage with respect to frequency, not constant power. If you have a speaker with a ruler flat impedance curve, then it will sound basically the same with tube or solid state. However, I've never seen a speaker with a ruler flat impedance curve. My Thiel CS3.7s have fairly flat impedance above 60-Hz, but they are still not perfectly flat. If you look at the impedance curves of most other speaker, they are very much like a roller coaster.



 

Damn! Those are some "mil-spec" looking amps!!, posted on October 22, 2013 at 08:16:58
rlw
Audiophile

Posts: 3347
Location: Near West Palm Bch, FL
Joined: August 29, 2006
 They'd be right at home in the on-board AV system of an F-22 [smile]! And it seems that you very much enjoy their sound. Wow, built to the hilt amps that also sound terrific, what a concept!

BTW, if you don't mind, what did you pay for the AmpZillas?

-RW-

 

That graph surely shows...., posted on October 22, 2013 at 08:22:02
rlw
Audiophile

Posts: 3347
Location: Near West Palm Bch, FL
Joined: August 29, 2006
 Some *very* well-matched speakers, those traces are virtually identical!! I believe this is one of the things that gave the better KEFs of the late-70s/early-80s their glorious sound - the drivers were hand-matched +- 0.5 db between pairs...

-RW-

 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 22, 2013 at 08:43:54
rick_m
Audiophile

Posts: 6230
Location: Oregon
Joined: August 11, 2005
 "I like these solid-state monos much more than the previous pair I had experimented with."

Excellent!

Not only that they will probably grow on you more over time. Even stuff with essentially the same technology varies quite a bit.

I learned this decades ago when I decided, for no particular reason, that I needed a bigger power Amp. I liked the sound of my 60WPC Citation 12 but wanted a bigger one. Mmmm, bigger better!

The upshot is that I ended up lugging home most all of the SS A/B monsters within in a thirty mile radius because despite all logic and reason, they didn't sound the same. I was just looking for more power and maybe lower Zout and was really surprised to hear sonic differences at moderate levels. The story has a happy ending, I have been using the winner ever since and it's advantages transcend mere sonics: it makes a far better space heater than the old one did...

Rick

 

RE: Damn! Those are some "mil-spec" looking amps!!, posted on October 22, 2013 at 09:20:04
AbeCollins
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  Since: February 2, 2002
 All of the metalwork (except heat sinks) is of 14 Ga. powder coated steel. The power supply transformer in each monoblock is a 2000VA toroid designed in house. The line cord is 12 Ga. with "welded connectors" instead of crimped. All internal connectors are gold plated. The mono amps are dense but fairly compact at 8.25"H x 10.5"W x 15"D.

I paid $5k for the ~1 year old pair.


 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 22, 2013 at 09:45:02
Trouser Trout
Audiophile

Posts: 286
Location: New England
Joined: August 25, 2010
 Not sure on that. When trying to find the cause of the channel imbalance on my Cronus Magnum I ran the headphone out without speakers connected with no ill effects.

 

Nice, posted on October 22, 2013 at 09:54:23
G Squared
Audiophile

Posts: 9088
Location: Washington, DC Metro Area
Joined: November 16, 2004
 I love what big quality SS power can do for a system. There is no such thing as too much headroom.
Gsquared

 

Jerry Siegel of 10 Audio certainly agrees with you..., posted on October 22, 2013 at 10:17:43
jeffreybehr
Audiophile

Posts: 5791
Location: Phoenix, Arizona
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Contributor
  Since: December 13, 2004
 ...awarding the A2000II a perfect 10LPs score.

 

The same reviewer gave another SS amplifier perfect score., posted on October 22, 2013 at 10:38:10
Beef Guinness Cutie Pie
Audiophile

Posts: 136
Joined: December 29, 2011
 To my amazement, it was Bryston 7B-SST2.

Don't know about you, but with me, credibility goes out of the window right there. Is Ampzilla "perfect" in the same way as Bryston, in other words and in the real world - slightly below "mediocre"? Who knows...

One other thing - I really have a problem with the idea of $8.5K amps having captive power cords. To me, it reflects certain design philosophy, or rather belief system, which I disagree with.

 

RE: The same reviewer gave another SS amplifier perfect score., posted on October 22, 2013 at 10:48:22
AbeCollins
Audiophile

Posts: 49475
Location: Maidenhead Grid Square DM79
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Contributor
  Since: February 2, 2002
 "One other thing - I really have a problem with the idea of $8.5K amps having captive power cords. To me, it reflects certain design philosophy, or rather belief system, which I disagree with."

And what belief system might that be? And how do you disagree?

As for the 10Audio review, I suppose more than one amp can have a 10 rating and sound different. Do all amps that have the same rating have to sound alike? Just posing the question.


 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 22, 2013 at 10:56:15
AbeCollins
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Location: Maidenhead Grid Square DM79
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 Interesting. I wonder if I can pull the power tubes from the Rogue integrated to save on power and heat, and run it temporarily as just a preamp.

I think I'll give Rogue a call or quick email.

Knowing that you ran yours w/o the speakers at least suggests to me that it won't harm the amp. Thanks.

 

RE: Power corrupts. Class AB not as good. Hardly!, posted on October 22, 2013 at 13:35:10
Jack D II
Audiophile

Posts: 1535
Location: Hot Springs, AR
Joined: June 17, 2009
 Get a Marsh Sound Design spolid state amp and forget about the typical solid state sound criticisms. And almost all other criticisms, too.

 

agreed , posted on October 22, 2013 at 14:55:04
Enzo
Audiophile

Posts: 67
Joined: November 20, 2000
 The Bryston was one of the worst sounding amps of many I've auditioned, second only to a Bel Canto digital integrated.

 

RE: agreed , posted on October 22, 2013 at 15:53:17
AbeCollins
Audiophile

Posts: 49475
Location: Maidenhead Grid Square DM79
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 The 7BSST2 were much better than the older Brystons I've heard a decade or more ago. In those days, I would choose Classe over Bryston every time. The main thing I didn't get from the current Brystons were any warmth or sweetness. They were too dry and sterile for me. However, they were tight in the bass, smooth, and very dynamic. I thought I could get 'there' with a tube preamp in front but I was spending too much time and effort on it.

The Ampzillas have a very different sound compared to the Brystons.

As for the captive power cord on the Ampzillas, this is not that uncommon on higher power amps. They ensure better contact and current delivery, and protect against some audiophool putting an inadequately rated designer cord on the amp. Krell does the same on some of their higher power amps.


 

That's true, posted on October 23, 2013 at 15:03:02
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Tube amps do prefer a relatively flat electrical load. But if the impedance of the speaker stays constant and so does the voltage, then the current will vary and vice-versa.

The basic issue is speaker design here. Speakers don't have to present tortuous electrical loads to sound magnificent. Flatter and higher impedance (speaker electrical load) is always "better" for any kind of amp. Sensitivity matters less.

 

RE: That's true, posted on October 23, 2013 at 16:05:54
John Elison
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Posts: 24056
Location: Central Kentucky
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  Since: January 29, 2004
 > But if the impedance of the speaker stays constant and so does the voltage, then the current will vary and vice-versa.

I'm not sure what you mean. Current equals voltage divided by impedance. If voltage and impedance both remain constant, then current must also remain constant. They are all intimately related by the equation:

Current = Voltage ÷ Impedance

Voltage is a force that pushes electrons through a circuit.

Current is the actual flow of electrons through a circuit.

Impedance is like a restricting device that limits current flow.

If voltage remains constant and impedance varies, then current will vary. Speakers are designed to respond to constant voltage with respect to frequency. If their impedance varies with respect to frequency and the amplifier applies a constant voltage, the current through the speaker must vary. However, a speaker's frequency response is dependent on constant voltage, not constant current. A solid state amplifier will provide constant voltage regardless of how the speaker's impedance varies; a tube amplifier will not. A tube amplifier will provide constant voltage only if the speaker's impedance does not vary. Since the impedance of all speakers vary with respect to frequency, solid state amplifiers and tube amplifiers will sound different from each other.

Best regards,
John Elison

 

Sorry., posted on October 23, 2013 at 19:49:34
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 That is what I meant to say. The current swing will offset the impedance change holding voltage constant. So, in the best of all worlds, a flat electrical load is what both kinds of amps really do best with.

 

I think those power cables have welded ends. nT, posted on October 24, 2013 at 20:13:32
Vic D
 m

 

Were your previous amps..., posted on October 29, 2013 at 14:41:23
DAVID
Audiophile

Posts: 772
Joined: September 26, 1999
 ...the Ayre MX-Rs?

 

Don't know about the 2nd edition..., posted on October 30, 2013 at 13:05:39
morricab
Distributor or Rep

Posts: 9360
Location: switzerland
Joined: April 1, 2005
 But the 1st ones sounded warm and a bit muffled and were handily outclassed in clarity and tone by a number of other amps we tried them against. We were using Apogee Divas as the speakers on test. They had kind of a (bad) tube warmth but without the midrange clarity of a better tube design...at least they weren't offensive.

 

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