Can you hear a difference in Sound between Audio Amplifiers?

[PENG]

You too? I am not advocating sighted comparisons either. I think they're both ineffective. (With the exception of the idle hiss that both you and I have experienced with some products.) I think we're stuck with measurements.

Finally, I can fully agree with you on this. People should focus much more on measurements that include more metrics that have impact on audible sound quality differences. Frequency response, THD and power output at 1 kHz into 8 ohms, SN ratio, XT and damping factors are probably not enough.

 

[Swerd]

People should focus much more on measurements that include more metrics that have impact on audible sound quality differences.

Before anyone can focus on any measurement that may or may not impact on audible sound quality, it is necessary to first establish that varying a measured parameter actually does have an audible effect. There is only one way to do that – with listening tests – properly controlled listening tests.

You simply cannot measure audibility with volt-ohm meters, oscilloscopes, or other lab bench test instruments. You must first make a clear positive correlation between a measured parameter and audibility.

If I have to repeat this until everyone gets it, I will.

 

[Irvrobinson]

If I have to repeat this until everyone gets it, I will.

Wake me when it's over.

 

[PENG]

Before anyone can focus on any measurement that may or may not impact on audible sound quality, it is necessary to first establish that varying a measured parameter actually does have an audible effect. There is only one way to do that – with listening tests – properly controlled listening tests.

You simply cannot measure audibility with volt-ohm meters, oscilloscopes, or other lab bench test instruments. You must first make a clear positive correlation between a measured parameter and audibility.

If I have to repeat this until everyone gets it, I will.

I always want to compare a good mix of music signal input to several preamp, and power amp (from entry level to high end) with the output signal from the same preamps, and power amps using a highly precise spectrum analyzer. The quantified difference can then be used in conjunction with listening tests.

Say the differences are not audible under specific conditions, people can still go with amps that compare well to the one measured best just for peace of mind. I trust such input/output signal waveform comparisons that should provide quantifiable overall results than the measurements of individual parameters such as THD, IMD, slew rate etc. I guess that's something I can only dream about because people who are qualified, and have the necessary equipment are likely not audiophiles/audiohoics, or can't justify doing such tests over what they are employed/paid to do.

 

[auronihilist99]

In regard to the blind test with Parasound amps and Crown XPS Series amps and the noise floor being higher with the Parasound, I would think it should have been the other way around due to the fact that the Crown XLS Series amps are 'Pro' amps designed for PA and not music. I'm a little disappointed with Parasound.

 

[AcuDefTechGuy]

In regard to the blind test with Parasound amps and Crown XPS Series amps and the noise floor being higher with the Parasound, I would think it should have been the other way around due to the fact that the Crown XLS Series amps are 'Pro' amps designed for PA and not music. I'm a little disappointed with Parasound.

When I auditioned the B&W 800D & 802D at the dealer, they were powered by Classe amps. I could hear the hiss noise clearly from 3 feet away.

Hiss noise and "noise floor" bothers me too.

None of my ATI amps have hissing noise from any distance.

But I don't think the hissing noise from Classe, Parasound, or other amps significantly adversely affects the sound quality once the volume level was up to 60dB and higher.

 

[Swerd]

I always want to compare a good mix of music signal input to several preamp, and power amp (from entry level to high end) with the output signal from the same preamps, and power amps using a highly precise spectrum analyzer. The quantified difference can then be used in conjunction with listening tests.

Say the differences are not audible under specific conditions, people can still go with amps that compare well to the one measured best just for peace of mind. I trust such input/output signal waveform comparisons that should provide quantifiable overall results than the measurements of individual parameters such as THD, IMD, slew rate etc. I guess that's something I can only dream about because people who are qualified, and have the necessary equipment are likely not audiophiles/audiohoics, or can't justify doing such tests over what they are employed/paid to do.

Peng – When you say it that way, it's perfectly reasonable.

I can get bent out of shape over how people word or mis-word things. When I was younger I used to get dinged by scientific paper editors over sloppy or ambiguous wording. They wouldn't reject a paper, but would insist on some specific language changes. I eventually learned how to avoid that.

I did the same thing about lab bench tests vs. listening tests. One measures electrical parameters (volts, ohms, etc.) and the other measures whether listeners report hearing a difference. They are different, but I do run into some stubborn resistance about this. So I occasionally get tough about it. I must have been tired last night.

I wish RichB and Irvrobinson were submitting papers for which I was an editor or reviewer. I would have a grand time stepping all over their statements .

 

[jinjuku]

You too? I am not advocating sighted comparisons either. I think they're both ineffective. (With the exception of the idle hiss that both you and I have experienced with some products.) I think we're stuck with measurements.

Thanks for the clarification.

 

[RichB]

This is an often cited article. The proposed "Amplifier Power Sink Test" is an interesting proposal for measurement with reactive loads (aka speakers):

The biggest problem is that no-one really knows what an amplifier will do when a reactive load reflects some of the power back into the amp's output. We can hope (without success) that the effects will be negligible, or we can try to make speakers appear as pure resistance (again, without success).
A test method already exists for this, and uses one channel of an amp to drive a signal back into the output of another. The passive amplifier is the one under test. It is also possible to use a different source amplifier altogether, since there is no need for it to be identical to the test amp. Use of a "standard" amplifier whose characteristics are well known is useful, since the source will be a constant in all tests. Differences may then be seen clearly from one test to the next.

- Rich

 

[auronihilist99]

When I auditioned the B&W 800D & 802D at the dealer, they were powered by Classe amps. I could hear the hiss noise clearly from 3 feet away.

Interesting. I own a Classe amp from the 90's and the only noise I hear is very slight hum if I place my ear directly against the speaker, otherwise, the amp has always been dead quiet. As far as future purchases, I'm still interested in the ATI power amps or the Crown XLS Series II amps.

 

[PENG]

This is an often cited article. The proposed "Amplifier Power Sink Test" is an interesting proposal for measurement with reactive loads (aka speakers):



- Rich

Few speakers will be so reactive to present phase angles of higher than 60 degrees at any significant part of its frequency response range. Even at 60 degrees, as long as the power amp is used well below it's rated output, say less than half, it will do fine. Note that cosine 60 degree=0.5. If the amp does get hot, just add a little external quiet fan on top. IMO if one needs 100W under the worst conditions (loudest one would listen to, allow for the highest dynamic peaks, etc.), get a 200W amp, then forget about the amp and focus on enjoying the music.

 

[jinjuku]

In regard to the blind test with Parasound amps and Crown XPS Series amps and the noise floor being higher with the Parasound, I would think it should have been the other way around due to the fact that the Crown XLS Series amps are 'Pro' amps designed for PA and not music. I'm a little disappointed with Parasound.

Amp circuitry is simply built around taking an input and spinning it up. Where things start to diverge is heat-sinking, active vs passive cooling etc... These are items that make a pro audio amp a pro audio amp.

 

[mtrycrafts]

This is an often cited
The proposed "Amplifier Power Sink Test" is an interesting proposal for measurement with reactive loads (aka speakers):
- Rich

David Rich at The Audio Critic used what is called a power cubed testing device.
This was varied from 8 Ohms to 1 Ohm and 60 degree inductive load to 60 degree capacitive load with a measure of the rail voltage sags. Some did terrible even with a big name, other like the behringer A500 did very well indeed.
Yes, voltage sag is a good indicator of things, how it would handle speakers.
http://www.biline.ca/audio_critic/audio_critic_web2.htm#dc2
Scroll down from that, 2nd article, you'll see the powercube result.

 

[Irvrobinson]

I wish RichB and Irvrobinson were submitting papers for which I was an editor or reviewer. I would have a grand time stepping all over their statements .

For a cultist, you have a mighty high opinion of yourself.

So you really think we need double-blind tests for audibility of artifacts 80-120db+ down from the fundamentals?

 

[Tulsa]

Looking for answers concerning pioneer elite VSX-LX301 receiver. Trying to connect speaker selector to zone 2 for outside speakers

 

[Swerd]

So you really think we need double-bind tests for audibility of artifacts 80-120db+ down from the fundamentals?

Absolutely not. No one can hear different sounds where one is 0 db+ and the other is 80-120 db down.

But if someone insisted on ruling out the possibility of hearing such things at higher levels, say ~25-40 db down, a blinded listening test would do it.

Making such a test double blinded is unnecessary and would add nothing to the results.

 

[herbu]

audio memory is a factor, unless you're switching in a matter of seconds.

That's why I said my imagined DBT would have "immediate" switching. Not a matter of "seconds". I'm finding it hard to understand why you don't believe this would be useful.

All the problems seem to be technical issues with providing a truly balanced and equal double-system that can immediately be switched back and forth. Is that really your objection? If such a double-system could be executed, would you still say it has no value to the consumer in selecting a featured component?

 

[Irvrobinson]

Absolutely not. No one can hear different sounds where one is 0 db+ and the other is 80-120 db down.

But if someone insisted on ruling out the possibility of hearing such things at higher levels, say ~25-40 db down, a blinded listening test would do it.

Making such a test double blinded is unnecessary and would add nothing to the results.

That's not what you seemed to be saying before, but whatever.

 

[Irvrobinson]

That's why I said my imagined DBT would have "immediate" switching. Not a matter of "seconds". I'm finding it hard to understand why you don't believe this would be useful.

All the problems seem to be technical issues with providing a truly balanced and equal double-system that can immediately be switched back and forth. Is that really your objection? If such a double-system could be executed, would you still say it has no value to the consumer in selecting a featured component?

For modern electronics, IMO, no value at all. If an amplifier has audible artifacts they will be easily measurable, and the amp should be avoided. I don't think comparative listening tests have any value for electronics.

Speakers are another matter altogether, but speakers vary so much that I prefer to compare to a reference than to each other.

 

[jinjuku]

For a cultist, you have a mighty high opinion of yourself.

So you really think we need double-blind tests for audibility of artifacts 80-120db+ down from the fundamentals?

Irv, I believe it's totally acceptable and reasonable to test peoples claims. As an example you have paid hacks like Micheal Lavorgna espousing 'night and day' and 'readily apparent' differences in the audibility of Ethernet cables where none can actually exist.

Now I KNOW that either SBT / DB ABX are totally worthless because there is zero difference. But then again I'm not testing a cable at this point. I'm testing them and their claim.

Claims are indeed testable: