Double Blind tests *did* show amplifiers to sound different

[MakeMineVinyl]

It seems like you're leading the witness..

As the witness is dragged out of the courthouse screaming, kicking and yelling about supposed conspiracy theories about listening to something....

 

[NTK]

No, but I don't believe they just throw up their first design either.

They get to "measure" it thoroughly, but not a "listen".

 

[MakeMineVinyl]

I have to be cheeky with respect and apologies - any UK made gear in that?

Nope, just US made stuff. I do have a pair of Wharfedale W60D speakers though. Both the midrange and tweeters in both speakers failed.

 

[MakeMineVinyl]

They get to "measure" it thoroughly, but not a "listen".

Actually, in a previous job in which I was designing a miniature camera for instrumentation, we hired an optical engineer who designed the "correction" lens for the Hubble telescope. He told some pretty horrendous stories of how the original engineers did all sorts of measurements and still screwed the pooch with an essentially useless lens system.

 

[NTK]

Actually, in a previous job in which I was designing a miniature camera for instrumentation, we hired an optical engineer who designed the "correction" lens for the Hubble telescope. He told some pretty horrendous stories of how the original engineers did all sorts of measurements and still screwed the pooch with an essentially useless lens system.

Of course mediocre engineers can't pull it off.

How did they come up with the correction system? Did they get to prototype it and test it? No. Again from theories, data from the messed up images, and prior measurements.

 

[MakeMineVinyl]

Of course mediocre engineers can't pull it off.

How did they come up with the correction system? Did they get to prototype it and test it? No. Again from theories, data from the messed up images, and prior measurements.

I have no idea how he did the Hubble correction. We hired him to design a lens for us, not so we could interview him.

 

[Frank Dernie]

Your future as an amplifier designer is guaranteed (to be short lived). But at least you can say you had it your way...while it lasted. Just don't expect me to fly on an airplane you designed.

I think you will find Serge had a pretty long career in audio electronics but failed somewhat as a hifi dealer since he told people the truth, which they had not heard before, and things like "you don't need to upgrade your amplifier it is already audibly transparent" to a potential customer, instead of assuring them the latest item would "blow what they had out of the water" and recommending expensive cables to go with their new purchase.

 

[sergeauckland]

Your future as an amplifier designer is guaranteed (to be short lived). But at least you can say you had it your way...while it lasted. Just don't expect me to fly on an airplane you designed.

Although I never designed equipment for consumer HiFi, I designed several pieces of pro equipment for tape duplication, recording and broadcasting studios and some Test & Measurement equipment. In no case did we ever do any subjective listening tests, nor did our customers on acceptance. They simply ran a set of standard measurements and then passed the equipment as fit for use.

I was fortunate in my career that my customers were experienced engineers who knew exactly what they were buying and why. When I tried to be a HiFi dealer I was spectacularly unsuccessful as I applied the same criteria to selling amplifiers as I had previously to broadcast infrastructure, and couldn't understand why my customers were different.

S.

 

[Vasr]

I only have first-hand experience with Halo. I would suggest that there's no sound shaping of any sort.

Depends on what you interpret sound shaping as. Halo amps/pre-amps are based on the Curl design philosophy part of which holds higher harmonics are bad and engineered for it. Typically you will find that these designs have relatively higher second and third harmonics which are more tolerated in that philosophy (how audible they are is a different question) and the higher order harmonics pattern sharply attenuated.

Not different from the design philosophy whether you agree with it or not that negative feedback should be minimal in other designers at the cost of higher distortion.

In Class A/B amps, designers also express their individual goals by utilizing different thresholds of Class A and Class AB operation trading off crossover distortion for longer range of cleaner Class A at lower levels. Will they be caught in a higher power output measurement, no. Can the characteristics be caught in a measurement at different power levels? Certainly, it is not voodoo magic. But will some users observe a difference and prefer some amps at the levels they listen to because of it? Absolutely. That is the point of the design choice.

If you interpret sound shaping as amps applying some "Harman curve" to the sound, no that was not what I am talking about.

There is a wide spectrum of characteristics between a Benchmark AHB2 pattern and a cheap Behringer PA amp pattern with very audible distortion. Some of these are engineering mistakes, some of these are by intention.

So, amps as compromise designs can be designed to different goals of distortion (levels or patterns) than the absolute goal of low distortion. I was identifying amps that have such design goals by intention.

 

[SIY]

Depends on what you interpret sound shaping as. Halo amps/pre-amps are based on the Curl design philosophy part of which holds higher harmonics are bad and engineered for it. Typically you will find that these designs have relatively higher second and third harmonics which are more tolerated in that philosophy (how audible they are is a different question) and the higher order harmonics pattern sharply attenuated.

Curl's huckstering claims aside, the distortion spectra look pretty typical, i.e., good. I've yet to measure an amp that didn't have 2nd and 3rd as the predominant harmonics. Mine on the JC5 will be published shortly, but here's Stereophile's measurements of another model. I don't see anything here that would be atypical for old-school AB amps or anything likely to be audible.

 

[MakeMineVinyl]

Although I never designed equipment for consumer HiFi, I designed several pieces of pro equipment for tape duplication, recording and broadcasting studios and some Test & Measurement equipment. In no case did we ever do any subjective listening tests, nor did our customers on acceptance. They simply ran a set of standard measurements and then passed the equipment as fit for use.

I was fortunate in my career that my customers were experienced engineers who knew exactly what they were buying and why. When I tried to be a HiFi dealer I was spectacularly unsuccessful as I applied the same criteria to selling amplifiers as I had previously to broadcast infrastructure, and couldn't understand why my customers were different.

S.

I've designed some pro gear too, and in those cases never did any listening tests beyond making sure it didn't have buzz/hum or noise when connected to other gear in a real world studio situation. Different industry.

 

[sergeauckland]

I've designed some pro gear too, and in those cases never did any listening tests beyond making sure it didn't have buzz/hum or noise when connected to other gear in a real world studio situation. Different industry.

But should it be? What's the difference between a piece of pro-audio equipment and a piece of consumer audio equipment? Why should the criteria for design and manufacturing be different?

I accept that some people may prefer a solid aluminium box, hewed from the solid as opposed to a black 19" rack mount case, but apart from the cosmetic, what distinguishes pro from consumer? (other than Bullshit)

S

 

[Vasr]

Curl's huckstering claims aside, the distortion spectra look pretty typical, i.e., good. I've yet to measure an amp that didn't have 2nd and 3rd as the predominant harmonics. Mine on the JC5 will be published shortly, but here's Stereophile's measurements of another model. I don't see anything here that would be atypical for old-school AB amps or anything likely to be audible.

Sorry, you are missing my point. It isn't a binary of "good" vs "bad". So, I will just leave it at that disagreeing with you.

 

[SIY]

It isn't a binary of "good" vs "bad".

I'd agree- it's not "good" vs "bad," but rather, it's "transparent" vs "colored." And the vast majority of modern electronics are "transparent." The kayfabe is to try to differentiate in a parity market.

 

[Feanor]

I think you are confused. The ABX test is the easy environment in which to distinguish one amp from another. If this test is failed it defies common sense that there will be actual perceptible differences that will be discovered in everyday use. The latter presents profound obstacles to making any kind of comparison between audio gear that has similar performance specs.

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There are well established reasons for why you perceive that amps sound different. In almost all real world playback environments two amps will never sound exactly the same.

What people don't acknowledge is that the perceptual biases that cause us to hear audio differences when none truly exist is that they actually do make things sound different. The perception of difference is not an 'illusion' or an 'imagined perception' it is a real, actual perceptual difference.

Even playing back the exact same passage on the exact same system will lead to different perceptions of sound. Our minds are constantly adjusting our perception and focus.

Couple this with the many objective reasons why comparing two amps in the real-world will lead to the conclusion that they sound different:
- Unless the amps have some kind of super calibrated gain structure, playbacks levels between amps will be actually different
- the problem of level matching is compounded by the different gain structures and resolution of the volume knobs.
- one amp might not be operating to spec
- tube amps or vintage amps can have a non-flat frequency response
- if tone controls are available on either amp, this can seriously compound efforts to understand how the amp sounds.

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This discussion is the 'vampire debate' of audio and it's about as settled as anything can be that competently designed amps are sonically in-distinguishable under specified conditions. This has been proved over and over with ABX testing.

To decide whether the results of such ABX testing are meaningful to us, potential user of an amplifier, requires interpretation and an analysis of how the conditions for these ABX tests relate to 'real-world' listening concerns.

Richard Clark ran a relatively famous $10k challenge for anyone who can distinguish two amps in a blind ABX test. Nobody ever claimed the prize after 100s of iterations. (If you've never read about this, it is truly a fascinating experiment worth learning about https://www.stevemeadedesigns.com/board/topic/193850-richard-clark-10000-amplifier-challenge/)

He had some strict conditions (strict in the sense that they must be met, not that they imposed unrealistic expectations on the amps or listeners)

- amps must be commercially available from reputable companies
- amps must be working (functioning at spec)
- test is performed on dynamic speakers (as opposed to something like an electrostatic design)
- amps level must be kept under either clipping or 2% THD 20Hz to 10kHz
- must be level matched to .05 db (on both speakers)
- absolute polarity and L/R are consistent between amps
- if the amps have a different frequency response then one must have some EQ applied to make them the same
- amplifiers must be brand name, standard production, linear voltage amplifiers
- program material must be commercially released music

Within these constraints are a wide range of possibilities and parameters under which the test could be conducted!

Contenders could:

- pick any two amps to compare (including car amps, tube amps)
- use any speakers
- use any music
- control the level of the playback
- can take as long as they want and switch between amp A and B as many times as they want
- if EQ is applied to equalize frequency response they can pick which amp gets the EQ

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The question for a potential user of an amp is: do the conditions and results of a test like the Richard Clark $10k Amp Challenge provide meaningful guidance on the selection of an amp suitable for purpose?

I argue that this provides a ton of useful, practical information for a consumer. It eliminates the worry about aspects of amp performance that are very difficult to impossible to evaluate in normal listening environment.

Thank you. A very learned and well reasoned treatist.

I don't find much to debate except that audiophiles do not evaluated amplifiers (or other components) in the highly constrained environment of that Blind ABX test. Therefore it doesn't seem axiomatic or common sense to me that the Blind ABX test would reveal all sonic differences.

Audiophiles tend to evaluate in "real world" environments and conditions. But this is not to say that audiophiles ignore "real world" difference altogether; on the contrary, most make quite some efforts to ensure that the component being evaluated is in an "all else equal" situation.

The bottom line for me is that I hear differences between amplifiers, (preamps, DACs, etc.), more often than not. There was a time, but it's the case no longer, that I worried about tiny differences -- which indeed could be my imagination or mood -- but nowadays I tend to the most the more significant differences only. For me, (if not for you), this implies that these "significant" differences are more likely to real than not. In my recent review of ICEpower 200ASC, (https://www.audioasylum.com/forums/amp/messages/23/235714.html ), I made three definitive statements about the ICEpower versus the 12X more expensive Pass Labs X150.5 amp: (i) the former is as detailed & transparent as the latter, (i) the former is a bit bright on the top end, and (iii) the former was slightly less "warm" than the latter in the mid-range. In all other aspects I simply said that the two were comparable. Oh, and I also said that both the ICEpower and Pass were basically better than the Class A Audio amp in all respects.

Incidentally, re. the Class D Audio amp, this amp was soundly trashed in his review & measurements of the essentially identical SDS-450 model. Amir didn't, however, to so far as to say the the that amp was broken. I guess I wonder by folks here care so much about impeccable measurements when this Class D Audio amp, not being "broken", ought to sound indistinguishable from say, the Benchmark amp.

But some may have noticed that I promised SIY that I would submit to blind testing if I could control certain parameters of the test: this promise stands.

 

[Sal1950]

Does the amplifier clip off sound when it enters sleep? Does it clip off sound when it wakes up? Does the amplifier make strange noises or pops when it wakes up/goes to sleep? These things can only be determined by critical listening. If I just measured things, and shoved it out the door, I'd be toast.

Good point of outside the box things I didn't think of. Checking for things that can happen when the amp isn't inside it's normal operating envelop. Don't seem that bursts of noise or volume changes sound like anything that would require "critical" listening though.. And having some measurement gear hooked up to it would reveal the issues under these circumstances as well as a speaker.

 

[Sal1950]

I made three definitive statements about the ICEpower versus the 12X more expensive Pass Labs X150.5 amp:

Measurements of Pass amps have shown that he tweaks them to sound a particular way and doesn't shoot for total transparency.
If that is so, then we would expect there to be a audible difference.

 

[SoundAndMotion]

I don't find much to debate except that audiophiles do not evaluated amplifiers (or other components) in the highly constrained environment of that Blind ABX test.

I’m afraid you’ve been misinformed or you misunderstood. There is no requirement for ABX tests that a highly constrained environment be used. There are some requirements, but you can listen the way you normally do in your home.

 

[MakeMineVinyl]

Good point of outside the box things I didn't think of. Checking for things that can happen when the amp isn't inside it's normal operating envelop. Don't seem that bursts of noise or volume changes sound like anything that would require "critical" listening though.. And having some measurement gear hooked up to it would reveal the issues under these circumstances as well as a speaker.

You'd be surprised at how critically you have to listen for little noises and responses from the amplifier during situations like this. It literally takes hours with all sorts of program material to finally be able to sign off the design. There's no test equipment on Earth that can evaluate the subjective sound of leaves blowing in a soundtrack and how it relates to an amplifier not clipping those sounds as it goes to sleep. Things like the integration time of the circuit which listens to the audio and a lot of other details. And of course failing to catch these things would be extremely critical if a customer calls to complain about it!

 

[MakeMineVinyl]

But should it be? What's the difference between a piece of pro-audio equipment and a piece of consumer audio equipment? Why should the criteria for design and manufacturing be different?

I accept that some people may prefer a solid aluminium box, hewed from the solid as opposed to a black 19" rack mount case, but apart from the cosmetic, what distinguishes pro from consumer? (other than Bullshit)

S

Pro audio gear is more utilitarian. That's not to say there's some progear like microphone preamps don't have a lot of voodoo mystique in their marketing. They do.