Can you hear a difference in Sound between Audio Amplifiers?

[RichB]

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.

The test proposed intended to test amplifier performance driving a reactive load. I don't believe the power-cube is multi-tone reactive and also does not include distortion measurements; Nor does it measure linearity when below maximum power.

- Rich

 

[Irvrobinson]

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.

Heh, heh, well, you've got me on this one. I think that idiot should be sentenced to pay for a 1000 participant DBT, and 10 hours of instruction on how to properly interpret the results from Swerd.

 

[RichB]

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.

It's anecdotal but a few years back, my right Salon1 speaker did not sound right. IRV suggested using pure tones straddling the crossover frequencies, sure enough, there were artifacts 40 DB down. I replaced the driver and measured again. Problem solved. So yeah, it seems that 40 DB down is audible.

Gene has reviewed amps which bench well but have had observable differences in bass response driving his 8T's. I believe him

Long term listening has value.

Does that make me a @Swerd/@Irv love child? (yuck).

- Rich

 

[jinjuku]

Gene has reviewed amps which bench well but have had observable differences in bass response driving his 8T's. I believe him

Long term listening has value.

Does that make me a @Swerd/@Irv love child? (yuck).

- Rich

Not surprising as low frequencies require much more of an amps power supply.

If you were a love child product of those two you would have horns.

 

[jinjuku]

Heh, heh, well, you've got me on this one. I think that idiot

I figured I had you check-mated with that one

 

[Swerd]

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

I made an effort to say things completely and avoid shorthand. That always seems to help.

 

[mtrycrafts]

The test proposed intended to test amplifier performance driving a reactive load. I don't believe the power-cube is multi-tone reactive and also does not include distortion measurements; Nor does it measure linearity when below maximum power.

- Rich

Well, I am sure they measure those parameters the way others measure it. See figures 2 through 6.
The power cube is strictly the amps response to loads and phase shifts caused by speakers.
Yes, it seems to be at one frequency that may of may not be sufficient but it does show behavior that no others do.

 

[3db]

I reread the last couple of pages of this thread and there seems to be some re-occuring points made:

1. testing of amplifiers is far from being accurate or complete.
2. Not enough testing/modelling done of amplifier specific parameters (ie slew rate, crossover distortion, etc) and how it correlates to a perceived difference in sound.

The points below are my pet peaves and are not necessarily due to this thread but the so called "audiophile golden ear" attitude. (I'm not pointing at you Rick [ your ears are actually more fleshy in appearance than golden ] as you are not exhibiting that typical behavior and should be commended for being open minded and civil. )

1. Not enough value/importance given to blind listening test comparisons.
   
2. Close to the above point but subtly different... sight bias and its effect on our hearing perception is totally scoffed at by the audiophile community.
   
3. Too much value given to sighted listening tests.

Its been my experience from listening to similarily powered amps driving the same speakers in the same acoustic setting and well within their power envelope that I could not detect any difference in sound between the different amps.

 

[Swerd]

I reread the last couple of pages of this thread and there seems to be some re-occuring points made…

I share your thoughts on this. You said it well, probably a lot better than I have recently. Thanks.

 

[RichB]

I reread the last couple of pages of this thread and there seems to be some re-occurring points made:

1. testing of amplifiers is far from being accurate or complete.
2. Not enough testing/modelling done of amplifier specific parameters (ie slew rate, crossover distortion, etc) and how it correlates to a perceived difference in sound.

I agree with this statement completely.
Crossover distortion occurs in speakers too

The points below are my pet peaves and are not necessarily due to this thread but the so called "audiophile golden ear" attitude. (I'm not pointing at you Rick [ your ears are actually more fleshy in appearance than golden ] as you are not exhibiting that typical behavior and should be commended for being open minded and civil. )

That Rick character thanks you, whoever he is

Its been my experience from listening to similarily powered amps driving the same speakers in the same acoustic setting and well within their power envelope that I could not detect any difference in sound between the different amps.

I expect this is the norm.

Since I have speakers that dip below 4 ohms, I wonder if the manufacturer statement "stable into 2 ohm loads" really tells speaks to the linearity and distortion levels when driving difficult reactive loads.

- Rich

 

[3db]

I agree with this statement completely.
Crossover distortion occurs in speakers too


That Rick character thanks you, whoever he is



I expect this is the norm.

Since I have speakers that dip below 4 ohms, I wonder if the manufacturer statement "stable into 2 ohm loads" really tells speaks to the linearity and distortion levels when driving difficult reactive loads.

- Rich

I happen to agree with you and thought the "Rick character" funny.

 

[brad1138]

Yes.

 

[steve64]

Yes! My speakers are a nominal 4 ohm load, MTMWW
design. originally, I powered them with a set of Emotiva
XPA 1-l class A monoblocks, sounded great. Got that old itch!! Soooo, I went out and bought a new Mcintosh MC-275
tube amplifier. I now bi-amp. Emotivas for the low end. Mcintosh for the mids and tweets. To me, it sounds
" richer, fuller ". I know, it's probably the cables!!
Just joking. Could be bias. I just love looking at that amp!
However, the difference is there.

 

[3db]

Tube amps and SS amps do not perform nor do they sound the same

 

[steve64]

I know. I thought this thread needed more humor. This hobby should be both expensive,( to keep
people out of trouble ), and fun.

 

[Art Vandelay]

When you start designing and building amplifiers you soon discover that sometimes small design changes can result in significant subjective outcomes.

I used to think that small changes to the harmonic distortion profile was the cause of most of the differences we hear, but it's more complex than that, and I've subsequently discovered differently.

The use of negative feedback and the way it's applied is actually the prime cause of most of what we hear, but not due to harmonic distortion.

Our ears appear to be very sensitive to very small changes in an amplifier's impulse response, and it's the way that feedback is applied that can either lead to an underdamped or overdamped impulse response, and often it's a combination of both at the same time.

In high global and local fb amplifiers, getting frequency compensation right is paramount to good subjective performance. And you don't need to get it very wrong to end up with either a dry grainy treble, or a treble that's too sweet and smooth.

 

[steve64]

I should have known better. I am sure that I COULD NOT, in a REAL DBT, tell the difference between
any new solid state amplifier design. MAYBE, I could tell the difference between a new solid state amp and a new tube amp. But MAYBE NOT.

In the early 1970's a Japanese(?) researcher presented a paper to the AES that, apparently, actually had a " GOLDEN EARED " individual. If I remember correctly. this guy could actually hear .06% distortion in
a turntable! Well, okay. I know I sure won't brag about my ears.

Anyway, I like Swiss mechanical watches and old Cadillacs.

You're gonna die.

Spend what you got an pretty gear and you'll find it just sound great.

 

[Speedskater]

Euphonic amplifiers be they tube or solid-state do not sound the same as accurate amplifiers (be they tube or solid-state).
Nor do euphonic amplifiers sound the same as each other.

If a person enjoys the sound coloration of an euphonic amplifier or system, that's great. But it's not better than an accurate system, it's different.

 

[KEW]

Gene has reviewed amps which bench well but have had observable differences in bass response driving his 8T's. I believe him

Of course, but I am betting if you measure a bunch of amps ability to perform with a 2.6 Ohm load (which is what the 8T's dip to), you will have a very, very high correlation between lab measurements and sound quality.
These amps may all bench well by normal standards, but if you are going to subject them to abnormal loads, then you should use measurements that reflect those loads.
This is hardly a demonstration of how we can hear things that cannot be measured; it is only a demonstration of how we can hear things that were not measured.
Most of us know that if we are buying an amp for Magnepans that we need to look for performance at low impedance and not just stick with the "RMS into 8 Ohms" specification. We recognize that the Magnepans are an exception to the normal conventions/shortcuts (as in only testing for mainstream applications) used on the measuring bench. The 8T's are in the same boat.

 

[V Gautam]

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