Blind Testing Amps

[AJ Soundfield]

Perhaps, they have found in listening, unexpected results. Once observed, a test was made that uncovered the source.

Yes, a measurement. That was obviously missed the first time. It happens.

I believe that everything that can be heard can be measured, but not everything heard is necessarily measured.

Correct. Electro-acoustic measurements can only measure electro-acoustics. They can't measure imagination, emotions, voices in head, feelings, etc, etc. One has to quantify what is to be measured.

Simply reciting, that everything can be heard is measured is simplistic.

See above,

Obviously, amps have different design goals and will measure to assure that they achieve them.
This is the nature of product development.
There are many "objectivists" in audio that have made up their minds and can be every bit as intransigent as those the pure subjectivist.

There are many who believe any measured differences bolster their "heard" differences in totally invalid listening tests, falsely presuming that any/all measured differences are audible, which they are not.

Personally, I want more and better measurements.
The "working within their limits" is near meaningless statement that cannot be determined.
Many amps wont accurately display when they are clipping, soft clipping, current limiting a transient, etc.
An AVR amp has a measurement goals but also, perhaps more important, reliability goals.
It is critical that these products operate and sound good to the target audience.
Those leaning objectivist (as I am), still need to probe the conditions of the listening session. There are weaknesses to all and any finding have limitations and may not provide meaningful efficacy for all systems.
- Rich

Start with better aka valid listening tests. If/when one finds something, that should prompt further investigation.
Until then, its all classic Wishful Thinking fallacy. A recursive, pervasive issue in audio.

cheers

 

[RichB]

Yes, a measurement. That was obviously missed the first time. It happens.


Correct. Electro-acoustic measurements can only measure electro-acoustics. They can't measure imagination, emotions, voices in head, feelings, etc, etc. One has to quantify what is to be measured.


See above,


There are many who believe any measured differences bolster their "heard" differences in totally invalid listening tests, falsely presuming that any/all measured differences are audible, which they are not.


Start with better aka valid listening tests. If/when one finds something, that should prompt further investigation.
Until then, its all classic Wishful Thinking fallacy. A recursive, pervasive issue in audio.

cheers

Likewise, wishing for all amplifiers to sound that same does not make it true.
It is human though.

- Rich

 

[AJ Soundfield]

Quick switching has known benefits and clearly an aspect of blind.
Did I say it was blind? NO.

Then whatever differences you thought you heard were also "non-blind".

Instantaneous switching is a hell of a lot better, then multi-day or even one minute change over.

Precisely what the AVA does, but with a critical aspect you're missing, randomized, not AB

Over where? I posted this information on ASR, I am not a coward as you infer.

No one inferred that and apologies if I missed. Link?

 

[AJ Soundfield]

Likewise, wishing for all amplifiers to sound that same does not make it true.
It is human though.

No its daft, since all don't and no rational person says/believes that.

 

[RichB]

No its daft, since all don't and no rational person says/believes that.

Benchmark believes and built an amp that is provably transparent by accepted science below the audible threshold of 0 dBFS.

Let's see what the non-daft know:

• All amplifiers do not behave the same into reactive loads
• Numerous Stereophile measurements show amps, even SS amps that vary greater than .1 dB. The accepted audible threshold.
• Amplifier design thresholds are not understood and fully characterized
• Not all amplifiers are measured equally and do not measure equally.

Do you know this or are you daft?

- Rich

 

[AJ Soundfield]

Do you know this or are you daft?

I know that all amps don't sound the same as some would daftly claim

 

[AJ Soundfield]

Numerous Stereophile measurements show amps, even SS amps that vary greater than .1 dB. The accepted audible threshold.

Do you know this or are you daft?

- Rich

0.1db is an absolute threshold limit, frequency bandwidth dependent and only with isolated headphones, so zero relevance to said loudspeaker in real room amps.
What was the second question again?

 

[RichB]

0.1db is an absolute threshold limit, frequency bandwidth dependent and only with isolated headphones, so zero relevance to said loudspeaker in real room amps.
What was the second question again?

No further question, the defense rests.

- Rich

 

[RichB]

I know that all amps don't sound the same as some would daftly claim

Honestly, apply some specifications to these claims. SINAD, distortion, topology, linearity into load, output impedance, etc.. Otherwise, it's carnival barking really.

- Rich

 

[AJ Soundfield]

Likewise, wishing for all amplifiers to sound that same does not make it true.

it's carnival barking really.

Kinda. But really a strawman argument.

 

[AJ Soundfield]

Numerous Stereophile measurements show amps, even SS amps that vary greater than .1 dB. The accepted audible threshold.

No further question, the defense rests.

Cite your evidence for this claim.
I have AES and ASA membership
Thanks

 

[Mike-48]

"It"?

"It" in this context in a statistical discussion means the postulated effect, if it is nonzero.

 

[AJ Soundfield]

"It" in this context in a statistical discussion means the postulated effect, if it is nonzero.

Ok we're on the same page. IOW zero "it" has been demonstrated...and thus "missed" in the test, statistically or otherwise.
Think we agree chasing negative proof isn't wise.

cheers

 

[Mike-48]

Ok we're on the same page. IOW zero "it" has been demonstrated...and thus "missed" in the test, statistically or otherwise.
Think we agree chasing negative proof isn't wise.

It seems we're on the same page in general, but I do not agree with your wording. Formally, a zero effect never can be demonstrated. One can't prove that unicorns (say) don't exist. All one can say is that none have been detected yet. Maybe one will, given better instrumentation or a more thorough survey. (We have, in fact, located living examples of species previously thought extinct.)

So chasing negative proof isn't just unwise, it's logically impossible. No one can demonstrate that any factor in audio is zero, just that we haven't been able to detect that effect, which may or may not be zero. Since audio is meant to be listened to, detectability is inextricably tied up with not just what we measure or listen to, but with the listener's abilities.

I am grateful that some individuals use listening to improve their measurement suites, just as I'm grateful that some use measurements to improve sound. I'll leave it there.

Cheers!

 

[Sonnie]

My philosophy, albeit far from expert (probably better labeled my opinion), is that since no one has proven there are differences in amps if used within their designed limits (not sure why anyone would want to use them outside of their designed limits), and that thus far there is at least some proof presented that there are no differences in those same amps, causes me to lean to the side that there are no differences for me to chase after, until those proofs change appropriately.

I fully agree that there may be some differences in amps out there, and when someone can prove to me (other than by their human ears) that it's a worthwhile audible difference that will improve my listening pleasure (outside of flashing warning lights and power), if it's within my financial abilities, I'll certainly give it a go.

For those that claim they hear differences and it causes them to buy one amp over another, I say to them... congratulations... get after it... spend the money. I spend it for reasons that others might think is silly to them. People buy various things because of different reasons. If it creates or improves audio nirvana for you, by all means... get it... just do it, and forget what anyone else might say about it.

The only thing audio that I can 100% say has made a significant difference to me is speakers... after that is equalization equipment/methods. Otherwise... amps (provided they have the power), cables and sources... sound all the same for me. Never heard any of the latter ever make an improvement in my systems.

 

[AJ Soundfield]

So chasing negative proof isn't just unwise, it's logically impossible.

Exactly as I said and agree. Thus zero need to do so.

No one can demonstrate that any factor in audio is zero, just that we haven't been able to detect that effect, which may or may not be zero.

What "that effect"?? This is the "It" again. Its either demonstrable, or a wishful thinking fallacy. I'll ask again, how is "that" and "it" being detected? Using what specific, valid only method of detection?

Since audio is meant to be listened to, detectability is inextricably tied up with not just what we measure or listen to, but with the listener's abilities.

Absolutely agree. So yes, if you claim to "hear" "that", "it", etc, or run faster than Usain Bolt, then you must be able to demonstrate so. Simply claiming that you can, cannot be taken seriously by anyone familiar with science, logic, burden of proof, etc. Hopefully we agree there. So when someone claims detection of difference between 2 SS amps that there is zero reason for there to be a difference, we have a possible N-rays/Cold Fusion scenario. Either an extraordinary discover, or...

I am grateful that some individuals use listening to improve their measurement suites, just as I'm grateful that some use measurements to improve sound. I'll leave it there.

100% agree, with the caveat that these said individuals furnish/publish either their valid and/or N ray results for peer review, not just "rumors" of they did this, heard that. If youre from the scientific field as I suspect, we should be in 100% agreement there too.
So much respect for Dr Toole et al.

cheers

 

[RichB]

Cite your evidence for this claim.
I have AES and ASA membership
Thanks

Demanding evidence but supplying none.
A paid membership does not lend credence to an argument.

- Rich

 

[AJ Soundfield]

.1 dB. The accepted audible threshold.

Demanding evidence but supplying none.
A paid membership does not lend credence to an argument.

Ok, so you made that up. Thanks.

 

[RichB]

Cite your evidence for this claim.
I have AES and ASA membership
Thanks

My philosophy, albeit far from expert (probably better labeled my opinion), is that since no one has proven there are differences in amps if used within their designed limits (not sure why anyone would want to use them outside of their designed limits), and that thus far there is at least some proof presented that there are no differences in those same amps, causes me to lean to the side that there are no differences for me to chase after, until those proofs change appropriately.

There are amps that have indicators to alert users when they are outside their limits.
Here are a couple videos from Audioholics that covers the topics of amplifiers sound differently.
Admittedly, there are amplifiers that sound similarly good.
This is the EE, real-word, and IMO balanced viewpoint.

There are no perfect amplifiers but there are perfect enough.
As an end user, we do not know the design of every amp, it's behaviors as a perfect voltage source.

I don't think you have to be an expert to understand the concepts of voltage source, limiting when amps are not clipping, output variance into reactive load.

I think we all write with assumptions in mind. For example, you could compare a inexpensive Yamaha receiver with 90 WPC driving your ML 15As. If you keep at 2.83 volts, would still be under 10 watts. So, not clipping. I suspect you will hear a difference. I suspect the Yamaha protection circuitry will limit the output and it is absolutely working within its designed limits.

Stereophile provides interesting measurements into load with data you cannot get from the specs or a white paper.
Parasound Halo A 21+ power amplifier Measurements | Stereophile.com
This is beefed up version of the A21. These tests are at 2.83 volts, they do not include distortion measurements.
The A21+ is down .75 dB over the entire spectrum into a 2 Ohms resistive load.

Sterephile's measurements of the AHB2 show better but not perfect performance.
Benchmark Media Systems AHB2 power amplifier Measurements | Stereophile.com
The AHB2 varies from .25 for most of the range dropping down .75 dB at 20 kHz.

You will find this on many amps and the number can, but don't always. get large on tube/valve amps.
There is merit the the your findings about amplifiers but absolutes statements are not defensible, though some here think it is the other way around.

- Rich

 

[AJ Soundfield]

There is merit the the your findings about amplifiers but absolutes statements are not defensible,

Like sighted tests

 

[RichB]

Ok, so you made that up. Thanks.

Juvenile.

I have no the time to site it now, I work for a living. There have been studies that .1 is established to be the lowest level where tests have proven that volume differences can be consistently identified.

The accepted standard for amplifier level matching is .1 dB and that has been out there forever.

- Rich

 

[Sonnie]

There are amps that have indicators to alert users when they are outside their limits.
Here are a couple videos from Audioholics that covers the topics of amplifiers sound differently.

There is no proof there that amps don't sound the same. He has a Dayton amp that is not properly designed to drive a 4 ohm load and it was rolling off in the highs. While it may be spec'd to handle 4 ohms, what he proved was that it was NOT in fact designed properly. A perfect example of an amp operating outside of its limits. Very deceiving video for the title.

IIRC... again HTS deleted the graphs, but all of the amps we measured had identical frequency response. If you include an amp that has a rolled off frequency response, you get into comparing apples to oranges... it's a different product.

I think we all write with assumptions in mind. For example, you could compare a inexpensive Yamaha receiver with 90 WPC driving your ML 15As. If you keep at 2.83 volts, would still be under 10 watts. So, not clipping. I suspect you will hear a difference. I suspect the Yamaha protection circuitry will limit the output and it is absolutely working within its designed limits.

See... for me... an amp that has its protection circuitry kick in to limit the output, and keeps on allowing output is not really performing within its limits. We compared an inexpensive Denon AVR with all those amps we tested. It clearly was not capable of, nor designed to handle ESL speakers at loud volumes, so we could hear it compressing the sound at super loud volumes. Kept within how the AVR should really be used, no one present could hear any differences... it literally had to be cranked up to extremely uncomfortable levels to hear it struggling. A proper designed amp that is intended to be used with an ESL will not do that... otherwise it is not designed for it.

Once again... I am NOT saying you or anyone else can not hear differences in amps. I am simply saying no one has provided any proof of it... ever... that I have read or witnessed. Someone simply saying it does not provide proof.

 

[RichB]

There is no proof there that amps don't sound the same. He has a Dayton amp that is not properly designed to drive a 4 ohm load and it was rolling off in the highs. While it may be spec'd to handle 4 ohms, what he proved was that it was NOT in fact designed properly. A perfect example of an amp operating outside of its limits. Very deceiving video for the title.

IIRC... again HTS deleted the graphs, but all of the amps we measured had identical frequency response. If you include an amp that has a rolled off frequency response, you get into comparing apples to oranges... it's a different product.


See... for me... an amp that has its protection circuitry kick in to limit the output, and keeps on allowing output is not really performing within its limits. We compared an inexpensive Denon AVR with all those amps we tested. It clearly was not capable of, nor designed to handle ESL speakers at loud volumes, so we could hear it compressing the sound at super loud volumes. Kept within how the AVR should really be used, no one present could hear any differences... it literally had to be cranked up to extremely uncomfortable levels to hear it struggling. A proper designed amp that is intended to be used with an ESL will not do that... otherwise it is not designed for it.

Once again... I am NOT saying you or anyone else can not hear differences in amps. I am simply saying no one has provided any proof of it... ever... that I have read or witnessed. Someone simply saying it does not provide proof.

There is proof that they measure differently into load. If you included clear reduction of output into load, there is evidence. I am not sure what is proof. Benchmark did some ABX testing of sinewaves and reports to have been able to identify cross-over distortion when listening at -70 dB. I don't think they are lying. Is this proof that crossover distortion is present.

If a group of people in a blind that find no audible differences did they prove that all amplifiers in all rooms, with all speakers behave this way.
It may well satisfy you and that's great. I suppose where you come down on the burden of proof matters.
Obviously, there is a range of performance and numerous variables.

My brother-in-law owned the Pioneer SC-7 class-D ICE amp AVR. It did not sound right to me driving his B&W CM10

The –3-dB point is at 49 Hz, and the –6-dB point is at 37 Hz. Impedance reaches a minimum of 3.72 ohms at 115 Hz and a phase angle of –69.15º at 69 Hz. —MJP

Bowers & Wilkins CM10 Loudspeaker Test Bench | Sound & Vision (soundandvision.com)

We upgraded his system to use an Oppo UDP-105 (I was a beta tester so got him a deal) and a pair of Outlaw M2200 monoblocks and we thought is sounded better.
It was later that Gene measured the SC-07 and reported the issue driving 4 Ohms loads.
There is no proof, but I we might be right

My last point, is one of human nature.
What then do we actually buy. Well, most who frequent amp threads don't AVRs for their main/music systems, regardless of speakers.
Some have tube amplifiers, I suppose you could buy these amps for aesthetics, to hear your room, or perhaps, you think they sound different even while professing that they do not
My dealer once told me that he has observed that amplifiers appear to be almost exclusively a male obsession.

I purchased the AHB2s for these reasons:

• A friend brought one over for an audition and I loved the detailed sound, obviously subjective.
• They measurements are SOA.
• Respected reviewers (those that buy good measuring gear) and not only liked them but bought them (a good sign).
• No transformers - My AT6000s had hum that could be heard from the listening position.
• No buzz - My Parasound A31 buzxed from the center and rear channel and could be heard from some listening positions.
• They weigh 13 lbs.
• They idle at 12 watts (measured) and allowed me to remove some Gelid fans, that I could also hear even when driven at 5 volts.
• They drive the Salon2s at sufficient volume for me and my family.

Every other amps I have owned has either had buzz or transformer hum: ATI, Parasound, Outlaw (ATI), Sunfire.

- Rich

 

[AJ Soundfield]

There have been studies that .1 is established to be the lowest level where tests have proven that volume differences can be consistently identified.

Then simply cite the studie(s). My AES/ASA membership will allow me to view the entire paper with details.
If its not there, cite your source. I'm not aware of any such paper. You are.

 

[AJ Soundfield]

I am not sure what is proof.

We know, but its published for peer review results of blind test, preferably double, using methods like ABX, Triangle, MUSHRA, etc.
Sighted "tests" are not.

Benchmark did some ABX testing of sinewaves and reports to have been able to identify cross-over distortion when listening at -70 dB. I don't think they are lying. Is this proof that crossover distortion is present

No, it's proof of belief, well known. If they have proof of such, they can publish for peer review, hopefully including all details, maybe using some music too.

If a group of people in a blind that find no audible differences did they prove that all amplifiers in all rooms, with all speakers behave this way.
It may well satisfy you and that's great. I suppose where you come down on the burden of proof matters.

Nope, this has been well covered, it proved only that no differences were detected under those conditions, which were valid. Adding to the evidence for. Since there is no against, then one can safely assume this to be true...unless shown otherwise, which like the Unicorns on dark side of moon, remain elusive.

My brother-in-law owned the Pioneer SC-7 class-D ICE amp AVR. It did not sound right to me driving his B&W CM10

We upgraded his system to use an Oppo UDP-105 (I was a beta tester so got him a deal) and a pair of Outlaw M2200 monoblocks and we thought is sounded better.

That sort of bias/belief preconditioning explains your sighted A/B test results perfectly. You got the results you wanted. Hence an AVA box would throw a wrench into that. Thanks for explaining.

cheers