Do all power amps sound the same?
virtualsamana
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#1
23rd September 2008
Old 23rd September 2008
  #1
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Do all power amps sound the same?

Watt for watt and driven within their linear range it sure seems so.

So in this instance: slew rates, the type of op-amps and capacitors used, and brand name don't seem to make a difference.

Amplifier Challenge Rules


As a side note: I am curious if a similar test could be done with preamps, driven within their linear range, and what the results would be. I am assuming this test would also include stacking the same preamp to see if an audible difference was noted in that regard.
#2
23rd September 2008
Old 23rd September 2008
  #2
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Thats false.

All amps CAN sound the same to some ears in some set ups with some material..

OTOH MOST amps can be separated from eachother in level matched controled blind tests at levels well below clipping.

Most amps (and other electronics) do color the signal audibly and while I'm sure there are one or two that colors the same most will sound different. The same goes for CD players.

Line level amps are the gear that is most likely to be transparent, partly because they are transmission links and also that they drive well behaved mostly resistive loads.


/Peter
#3
23rd September 2008
Old 23rd September 2008
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The "challenge" is normal A/B tester smug nonsense ("positive identification" as opposed to audible difference and preference is the giveaway). Yes, amps DO sound different from each other - sometimes very different. Unfortunately, those differences are not easily measured by THD specs (the Worst. Spec. Ever.), slew rates, output impedances, or other things hardware can do instead of our ears.

Having gone through a period of DIY tube amp building, one thing I learned is that all amps are distorting all the time, in some way or another. A corrolary to that is that measuring an amp's behavior with a 1khz sine wave test signal is about as relevant as comparing cars by how well they drive exactly 50mph in a straight line. MUSIC, as opposed to test signals, is wildly dynamic across 20-60 decibels and ten octaves.

Another important factor is how the amp deals with back EMF from the speaker (as opposed to a resistive test load). Speakers store electrical energy as mechanical energy, and then shoot it right back into the amp's output (and hence its feedback loops) in a time-delayed and frequency-dependent manner. That's not something to just handwave away!

Of course, this doesn't mean that more expensive = better. Cheap amps can sound good, and expensive amps can sound bad. But it ain't a bad rule.

The logic of the A/B test presented extends to mic preamps, doesn't it? Same thing, devices with the same specs that supposedly sound different to us "golden ears" but the A/B crowd says must sound the same because they weigh the same or something. But mic preamp differences are one of the first things we discover when we get serious about recording. Same thing with power amps.
virtualsamana
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#4
24th September 2008
Old 24th September 2008
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Thanks for your responses guys. I find this topic rather intriguing. I am curious how so many people can hear night and day differences between amps and yet when a challenge like this comes along people can't A/B a wallmart cheapo from a McIntosh or Bryston. It's faciating isn't it?


Quote:
Originally Posted by kludge View Post
The "challenge" is normal A/B tester smug nonsense ("positive identification" as opposed to audible difference and preference is the giveaway). Yes, amps DO sound different from each other - sometimes very different. Unfortunately, those differences are not easily measured by THD specs (the Worst. Spec. Ever.), slew rates, output impedances, or other things hardware can do instead of our ears.
So how would you explain the fact that no one has yet to pass Richard Clark's challenge? Without A/B/X testing how do we separate fact from fiction? In some audiophile circles there is certainty that $5000 botique cables sound drastically different than more reasonably priced canares or mogami. Those same people eschew the A/B/X testing that shows no discernible difference between cables exists. I also see some similarities in the external clocking debates. It seems people can hear what they want to hear and it has been scientifically shown that our perception greatly influences our hearing. That is why I see some validity to the blind A/B/X testing. Especially when it comes to components that are supposed to be linear or transparent.
#5
24th September 2008
Old 24th September 2008
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Most amps won't color the sound enough to worry about - you may be able to identify which is which in some pairs, but it's still subtle (if you stay in that "linear" region).

Change speakers or their position and there will be much larger differences....




-tINY

#6
24th September 2008
Old 24th September 2008
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I've always understood that differences in power amps are the result of design flaws or inefficiencies - that two well-made amps, even of different topology should output results indistinguishable from one another.

Now some might deem some of these "flaws" as euphonically pleasing leading one to say that this amp sounds better than that amp, but theoretically, there shouldn't be a difference between amps (I don't think).

I have never A/B'd amps. I figure it's the sort of thing that you'd have to flip between a dozen times to try and distinguish, and if I have to flip that many times, what's the point?

All I know is my monitors sound better with lots of power, so I use amps with lots of power, and I'm pretty sure it's my monitors that sound better, not the amp.
virtualsamana
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#7
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by tINY View Post


Change speakers or their position and there will be much larger differences....

-tINY


That has been my experience too. Speakers, room/positioning of speakers make much more of a discernible differences.
virtualsamana
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#8
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by travisbrown View Post
I

I have never A/B'd amps. I figure it's the sort of thing that you'd have to flip between a dozen times to try and distinguish, and if I have to flip that many times, what's the point?
Totally agree. It's just that when doing sighted tests people can think they hear a big difference so much so that they would be willing to spend thousands more. This is something that is truly fascinating for me.
#9
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by virtualsamana View Post
Thanks for your responses guys. I find this topic rather intriguing. I am curious how so many people can hear night and day differences between amps and yet when a challenge like this comes along people can't A/B a wallmart cheapo from a McIntosh or Bryston. It's faciating isn't it?




So how would you explain the fact that no one has yet to pass Richard Clark's challenge? Without A/B/X testing how do we separate fact from fiction? In some audiophile circles there is certainty that $5000 botique cables sound drastically different than more reasonably priced canares or mogami. Those same people eschew the A/B/X testing that shows no discernible difference between cables exists. I also see some similarities in the external clocking debates. It seems people can hear what they want to hear and it has been scientifically shown that our perception greatly influences our hearing. That is why I see some validity to the blind A/B/X testing. Especially when it comes to components that are supposed to be linear or transparent.
Because his challenge isn't to say they're different, or that one is better than the other - it's to IDENTIFY which one is which. I won't say A/B tests are invalid - but I will say they're generally misapplied, arguing that oranges = apples because both are fruit.

I think DIY informal A/B testing is a pretty valuable thing to do for any musician, and I make a point of doing it whenever I get new gear that duplicates the functionality of old gear. It can be instructive, too... when I got my first high-end guitar cable, I immediately A/B'd it against the cables I had. It was significantly better than the others, but the surprise was what came in second - some old, cheap Rapcos I've had for ages, which are supposedly inferior to the George Ls. At first listen, the George Ls sound better because they're brighter than the Rapcos... but really LISTEN, and the George Ls sound harsh and glaring. But to hear it, clearly, I had to do a serious A/B with an even better cable (Sommer). The Sommer was clear at the high end, not rolled-off like the Rapco but not harsh like the George L. So anyway, that's an example of how weird A/B testing can make things seem, and why it's not the easy answer the rec.audio.hifi crowd would like to pretend it is.
#10
24th September 2008
Old 24th September 2008
  #10
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Quote:
Do all power amps sound the same?
No.

Steve
virtualsamana
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#11
24th September 2008
Old 24th September 2008
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Originally Posted by squeegybug View Post
No.

Steve
Time to email Richard Clark and earn your $10K and bragging rights my friend.
#12
24th September 2008
Old 24th September 2008
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I know nothing of Richard Clark's challenge but I can tell you my experience.

I am the House guy at a small room and this past year the amp for the subs shot craps. I replaced the amp with a loner and immediately noticed a difference. As an experiment I didn't tell the guy who also mixes there and was to work the next night. The whole amp rack is powered on by flipping breakers from another location, so I knew he wouldn't notice a different amp in the rack.

He called me after the first band to tell me he thought something might be wrong with the system because the low end didn't feel right. Then he described to me the same things I had felt about the sound after changing the amp.

We both felt that the low end was still loud, but somehow felt softer. Also, it felt like the notes didn't decay as fast, like there was an unnatural decay to the low end. Basically it sounded like ass.

The next time I worked I double checked DSP settings and speaker polarity and everything was right.
#13
24th September 2008
Old 24th September 2008
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I'll ditto squeegybug's answer: NO.

Test or no test...
I'm not a scientist.. just a musician with a set of ears...

they sound different, feel different.. 3d field is different... phase coherency is different.
Yes.. components matter.
#14
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by virtualsamana View Post
Time to email Richard Clark and earn your $10K and bragging rights my friend.
Don't know anything about that, don't really care. What I do know is that in audio -- everything affects everything.

Steve
#15
24th September 2008
Old 24th September 2008
  #15
The AES dedicated the 1992 NYC conference on this exact subject: do amps sound different?

The golded ears of AES concluded, no there is no difference.

Another reason I'm not with that outfit anymore.

If you don't hear differences, the AES is correct. If you do, you must be wrong.

Those that propose cash rewards for proving this is not true set up the listening enviroment, all listening gear, source material, etc. They set it up so they can't lose. It's not that easy to see through a dirty window when you are evaluating the clarity of the glass. They are not interested in advancing the art but are simply advancing their publicity. If they were serious they would set up some neutral listening tests where the entire set up can be adjusted, changed, altered to fit the scenerio with others present and public involvment without cash reward gimmicks.

Jim Williams
Audio Upgrades
#16
24th September 2008
Old 24th September 2008
  #16
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Quote:
Originally Posted by stuntbutt View Post
I know nothing of Richard Clark's challenge but I can tell you my experience.

I am the House guy at a small room and this past year the amp for the subs shot craps. I replaced the amp with a loner and immediately noticed a difference. As an experiment I didn't tell the guy who also mixes there and was to work the next night. The whole amp rack is powered on by flipping breakers from another location, so I knew he wouldn't notice a different amp in the rack.

He called me after the first band to tell me he thought something might be wrong with the system because the low end didn't feel right. Then he described to me the same things I had felt about the sound after changing the amp.

We both felt that the low end was still loud, but somehow felt softer. Also, it felt like the notes didn't decay as fast, like there was an unnatural decay to the low end. Basically it sounded like ass.

The next time I worked I double checked DSP settings and speaker polarity and everything was right.
Dampening Factor. Possibly the most important spec when shopping for sub amps.

It's why Peavey and QSC are cheaper than (most)Crown and Crest watt for watt.
#17
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by Jim Williams View Post
The AES dedicated the 1992 NYC conference on this exact subject: do amps sound different?

The golded ears of AES concluded, no there is no difference.

Another reason I'm not with that outfit anymore.

If you don't hear differences, the AES is correct. If you do, you must be wrong.

Those that propose cash rewards for proving this is not true set up the listening enviroment, all listening gear, source material, etc. They set it up so they can't lose. It's not that easy to see through a dirty window when you are evaluating the clarity of the glass. They are not interested in advancing the art but are simply advancing their publicity. If they were serious they would set up some neutral listening tests where the entire set up can be adjusted, changed, altered to fit the scenerio with others present and public involvment without cash reward gimmicks.

Jim Williams
Audio Upgrades
Hey Jim, who are you accusing there? Sorry I didn't quite get it. I'd appreciate it if you could elaborate a bit more.

Thanks.

M.
#18
24th September 2008
Old 24th September 2008
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If that challenge didn't cost anything to take, I'd totally do it, but I probably wouldn't win the money, since it's a ridiculous test for the question you're posing. If the test were to identify whether or not I'm hearing a different amp from the previous one, I'm absolutely certain that I'd be able to do it with at least some of them. If that's the case with even one of them, then the answer to your question is, "No." It's that simple.

I'm not trying to be argumentative or accusatory here, but I really would like to know how many of you guys have heard the same set of speakers in the same place in the same room through different amplifiers and not been able to hear a difference.

Chris Garges
Charlotte, NC
virtualsamana
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#19
24th September 2008
Old 24th September 2008
  #19
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Originally Posted by cgarges View Post
If that challenge didn't cost anything to take, I'd totally do it, but I probably wouldn't win the money, since it's a ridiculous test for the question you're posing. If the test were to identify whether or not I'm hearing a different amp from the previous one, I'm absolutely certain that I'd be able to do it with at least some of them. If that's the case with even one of them, then the answer to your question is, "No." It's that simple.
Why do you think the test is ridiculous? The test is to identify whether you are listening to amp A or B. The FAQs state you get to supply the amps, monitors and source material. You can take as long as you like, and review your selection as often as needed before you submit your answer. I don't even think they would object to treating the space acoustically to your liking with some 703 panels before taking the test. Doesn't sound ridiculous at all to me, infact it sounds like they are trying to make it as objective as possible.

The problem with identifying whether or not you are hearing a different amp in only some of the trials is that it wouldn't be statically significant.

Clark says that in large groups he never observed variation more than 51/49%. Essentially the same as tossing a coin.
#20
24th September 2008
Old 24th September 2008
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Quote:
Originally Posted by virtualsamana View Post
Why do you think the test is ridiculous?
Because there's a huge difference in being able to correctly identify a number of specific amps and being able to tell if there's a difference. Those are two entirely different concepts. That's sort of like asking ten people to do an impression of WC Fields and then saying that because you can't tell who's doing which impression, there's no difference in the impressions.

I'm not even sure why I'm bothering to discuss this. I feel sorry for anyone making records that can't hear that there's a difference in a Crown XLS202 and a Bryston 4B. I can't make someone hear that difference, but I'm certainly not going to hire someone who can't to record something for me.

Chris Garges
Charlotte, NC
virtualsamana
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#21
24th September 2008
Old 24th September 2008
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Originally Posted by cgarges View Post
Because there's a huge difference in being able to correctly identify a number of specific amps and being able to tell if there's a difference.
Do you understand for the challenge you only have to identify the difference between TWO amps of your choosing? The FAQs state you could bring in a Crown XLS202 and a Bryston 4B and only need to identify which is which. Not identify other amps.
#22
25th September 2008
Old 25th September 2008
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Quote:
Originally Posted by cgarges View Post
I feel sorry for anyone making records that can't hear that there's a difference in a Crown XLS202 and a Bryston 4B.
I hear that.

One more thing; M-A-R-A-N-T-Z

Wow, wish I had one.
#23
25th September 2008
Old 25th September 2008
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Before I got my Brystons (I now have 3) I spent a lot of time trying to fix problems that weren't really there.
#24
25th September 2008
Old 25th September 2008
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The Swedish audio society LTS has done controled blind tests for decades on hifi and audio gear. There is only one amp (of hundreds) that have been impossible to hear in a before/after test. It was a beefy bryston after modification of the filtering.

Bryston did the modification to the amp after LTS reported that it could be picked out in a level matched blind test with statistical singificance.

That should be read as almost all amps that exists (and other gear as well) color the signal audibly.

Clarke and "AES" are simply wrong on this matter.


/Peter
#25
25th September 2008
Old 25th September 2008
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I'm so confused. If preamps can be different can't power amps be different?
virtualsamana
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#26
27th September 2008
Old 27th September 2008
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Originally Posted by audiostout View Post
I'm so confused. If preamps can be different can't power amps be different?
From Richard Clark's website:

"of course there are differences--some amps cost more because they are built better--perhaps they will last longer--or play longer without overheating--or have better resale value because they have more "brand appeal" or do more because they have more features--all I ever said was that WHEN THEY ARE COMPARED EVENLY THE SONIC DIFFERENCES BETWEEN AMPLIFIERS IS BELOW THE AUDIBLE THRESHOLD OF HUMAN HEARING"

Also, as Jim Williams stated previously, AES evaluated the question of sonic differences between power amps and came to the same conclusion as Clark.
#27
27th September 2008
Old 27th September 2008
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Originally Posted by virtualsamana View Post
... as Jim Williams stated previously, AES evaluated the question of sonic differences between power amps and came to the same conclusion [that there was no audible difference] as Clark.
Which was when, unless I misinterpret, Jim concluded that the ears of the AES weren't so golden after all.
#28
27th September 2008
Old 27th September 2008
  #28
Quote:
Originally Posted by Brent Hahn View Post
Which was when, unless I misinterpret, Jim concluded that the ears of the AES weren't so golden after all.
I've been testing and comparing power amps for years and it's rare if one doesn't have a sonic signature, yes, they do all sound different. The first test I would do is once gain levels were matched up I would connect one amp to left, another to the right. There was always a difference between the two. The test for the listener was to watch their heads. They would turn towards the better sounding amp.

Jim Williams
Audio Upgrades
PDC
#29
27th September 2008
Old 27th September 2008
  #29
PDC
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Quote:
Originally Posted by dykstraster@gmai View Post
Dampening Factor. Possibly the most important spec when shopping for sub amps.

It's why Peavey and QSC are cheaper than (most)Crown and Crest watt for watt.
Unfair over generalization. It is amp specific. There are some Peavey amps that were Crest designs. There are some Crown amps using switching technology that suck for bass too. What you said is all blonds suck worse than brunettes.
PDC
#30
27th September 2008
Old 27th September 2008
  #30
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Quote:
Originally Posted by Brent Hahn View Post
Which was when, unless I misinterpret, Jim concluded that the ears of the AES weren't so golden after all.
And the wonderful AES once said that jitter was non existent, and even if it did exist, it was not a major contributor to poor digital audio. Whatever. It's political. Whoever has the connections and the money invested in a product gets to push their agenda.

Take a walk through an audiophile store and you will here major differences between amps for various reasons.
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