Can you hear a difference in Sound between Audio Amplifiers?

[Johnny2Bad]

Anthem AVRs are solid products, my only observation is that they are slow for providing firmware updates. The majority of their products are assembled in Vietnam @ the same factory that originally nuilt the majority of Harman/Kardon and Marantz AVRs. We know this factory well have been sourcing from them for > 25 years, the parent company is based in Seoul, Korea.



The way the original FTC statue(73) reads..
There are primary disclosures and secondary disclosures, secondary disclosures must be in smaller font type and/or not bold. A major issue today is AVRs are distributed on a global basis so brochures, web pages have info for Euro spec products and they use terms like DIN power which confuses things even further.
Bottom line...
No one monitors/enforces these specs and the CE brands can get away with almost anything..



Just my $0.02...

Some other thread an OP was asking about a Yamaha AVR. I did a little digging, and found the North American spec sheet, no reviews (some verbatim press releases, some paraphrased press releases, some "reviews" that just look at features but no testing, and so on) which only listed single channel, 1 KHz, 6 ohm "dynamic power" or some such thing. BUT ... the EU spec sheet, for 220~240V 50 Hz operation, DID list the FTC compliant power rating. Absent from the 120V 60Hz spec sheet. Everything else was the same, so I assume it's an identical unit, performance-wise. (For reference the 6ohm pwr was 170 1 ch driven 1 KHz, the FTC compliant power was 130w 20~20KHz, 8 ohms, 0.08% THD, both channels driven*). There were no tests or listing of the full multichannel all channels driven spec.

* Not defined as such, though, so we don't know if the pre-conditioning requirement was met.

 

[AcuDefTechGuy]

same thing ..........

If the majority here are disciples of The Audio Critic (who believe that the differences in amp sound are insignificant), I wonder why 61% of the voters here think that amps do sound different?

So wouldn't that make the disciples of The Audio Critic a minority here?

 

[RichB]

If in possession of an AVR with a 4 ohm setting, it is worth listening to the amp in 2-channel mode at moderate levels (say 80DB). I have done this with the Yamaha RX-A820 driving Revel M20's.

The A820 Rated Output Power (20Hz-20kHz, 2ch driven) is 100W (8ohms, 0.09% THD).
The M20's were measured at Stereophile:

All the acoustic measurements of the Performa M20 were made using DRA Labs' MLSSA system and calibrated B&K and Mitey Mike II microphones. My estimate of the Revels' voltage sensitivity was a little lower than specified, at 84.5dB(B)/2.83V/m. Given the sophistication of Revel's measurement facilities and the agreement I had obtained between my figure and their figure for the Performa F30, I was surprised by this disparity. I rechecked my figures; no change.
The speaker's impedance was assessed using an Audio Precision System One; the results are shown in fig.1, with the tweeter-level control set to its maximum and minimum positions. The lowest impedance is with the control set to "+1," in which case the minimum magnitude is 4 ohms between 2 and 3kHz. The electrical phase angle varies quite considerably, with a worst-case combination of 5.9 ohms and 42 degrees capacitive angle occurring at 100Hz. Good 4-ohm-rated amplifiers will work best with this speaker.


Read more at https://www.stereophile.com/content/revel-performa-m20-loudspeaker-measurements#fGbPxR7bLbT1UQsP.99

The A820 sounds much better when in 6 ohm (not 4 ohm mode). Audioholics does not recommend using the 4-ohm settings in AVRs because of severe power limiting.

I find when 4-ohm mode is engaged the changes in sound is lacking dynamics. There is also likely increased distortion. I have heard amps distort when stressed but also listened to products that simply sound more compressed and not much louder when you turn up the volume. A peak that is limited is not easily identified since sound that is not produced is hard to hear.

- Rich

 

[RichB]

Perhaps other can weigh in here but here are some measurements taken of a SS 300 WPC amplifier that is available now. Stereophile uses two tone tests and perhaps that is unfair but at 100WPC there are multiple harmonics in the -35 DB range. At 1 watt the harmonics are much better at about -62 DB.

It is fair to say that this is a stress test but playing complex tones (music) could not these distortion for some amplifiers be much higher than measured using pure tones?

SS amplifiers tend to be more rigorously measured than AVR amplifiers, so I don't think there is comparable data.

- Rich

 

[ski2xblack]

If the majority here are disciples of The Audio Critic (who believe that the differences in amp sound are insignificant), I wonder why 61% of the voters here think that amps do sound different?

I don't think you're correctly interpreting what "disciples" of The Audio Critic believe. The Audio Critic never simplistically claimed that differences in amps are insignificant, or that all amps sound the same. Rather, they explicitly mentioned the caveats to amps being indistinguishable (the same caveats that are conspicuously missing from the poll, rendering the only rational response that most are giving, that they can sound different). So the 61% who responded that way to the poll are in complete agreement with what was published in The Audio Critic.

 

[AcuDefTechGuy]

So the 61% who responded that way to the poll are in complete agreement with what was published in The Audio Critic.

I don't think so.

I think the majority of the 61% voters think that all amps sound different no matter what the condition is.

I think the majority of the 61% voters think that all amps have a sound signature of their own.

And The Audio Critic does not believe that amps have a sound signature of their own.

So the real question is, do all amps have a sound signature of their own?

 

[AcuDefTechGuy]

Rather, they explicitly mentioned the caveats to amps being indistinguishable (the same caveats that are conspicuously missing from the poll, rendering the only rational response that most are giving, that they can sound different).

The poll was left 100% open-ended for a good reason - to stir responses.

Perhaps it's one of those "glass half empty" scenarios.

Per my recollection from reading The Audio Critic years ago, at the end of the day, the take home message was:

Amps don't have a sound signature of their own = All amps sound the same when comparing apples to apples and under the same exact conditions.

 

[mtrycrafts]

...

Per my recollection from reading The Audio Critic years ago, at the end of the day, the take home message was:

Amps don't have a sound signature of their own = All amps sound the same when comparing apples to apples and under the same exact conditions.

Dr. David Rich also examined all their tested amp topology to see if that can cause differences and did an AES conference paper on it. In essence, no contribution.

And, they used DBT protocols in their listening tests.

 

[AcuDefTechGuy]

Dr. David Rich also examined all their tested amp topology to see if that can cause differences and did an AES conference paper on it. In essence, no contribution.

I recall that part too.

My take-away oversimplified message from TAC was that at the end of the day, comparing apples to apples under the same exact conditions, all amps regardless of type (A, AB, H, D, etc.) sound the same because they don't have a sound signature of their own. The same goes for cables/wires, preamps, DACs, CD players.

 

[ski2xblack]

Well, it has generated a lengthy thread, even though its all old news. And yes, I suspect that a good proportion of the 61 percent are true believers of whimsical audio woo rather than Aczel-style empirical reductionist types.

The caveats haven't changed, but they are violated frequently in the real world, resulting in apples to oranges comparisons. AVR's with paltry dynamic reserves and/or low impedance load limitations get pushed beyond their clean limits, and voila, audible differences. Some class d amps have output impedance quite a bit above zero, as do opt coupled tube amps and a host of other oddball kit from the fringes, and they too will produce audible differences. It's all due to violation of the same constraints that Aczel published years ago. And there's a convincing amount of evidence that amps with low distortion, low output impedance, linear response across the audible band, and operated within their limits are audibly indistinguishable. Some folks just refuse to believe it.

 

[M Code]

If in possession of an AVR with a 4 ohm setting, it is worth listening to the amp in 2-channel mode at moderate levels (say 80DB). I have done this with the Yamaha RX-A820 driving Revel M20's.

The A820 Rated Output Power (20Hz-20kHz, 2ch driven) is 100W (8ohms, 0.09% THD).
The M20's were measured at Stereophile:



The A820 sounds much better when in 6 ohm (not 4 ohm mode). Audioholics does not recommend using the 4-ohm settings in AVRs because of severe power limiting.

I find when 4-ohm mode is engaged the changes in sound is lacking dynamics. There is also likely increased distortion. I have heard amps distort when stressed but also listened to products that simply sound more compressed and not much louder when you turn up the volume. A peak that is limited is not easily identified since sound that is not produced is hard to hear.

- Rich

Hmmm..
Very interesting...
In the 6 Ohm position the power supply secondaries are switched and current limited, however in the 8 Ohm position the amplifier will have more dynamics and power output even into 4 or 6 Ohms. If U are hearing a difference in the 6 Ohm position be sure the Parmetric EQ and Adaptive DRC are switched out as well as Speaker trims & YPAO settings are matched...

Just my $0.02...

 

[AcuDefTechGuy]

I am kind of disappointed that after almost 5 years, there are only 145 total votes.

 

[RichB]

Hmmm..
Very interesting...
In the 6 Ohm position the power supply secondaries are switched and current limited, however in the 8 Ohm position the amplifier will have more dynamics and power output even into 4 or 6 Ohms. If U are hearing a difference in the 6 Ohm position be sure the Parmetric EQ and Adaptive DRC are switched out as well as Speaker trims & YPAO settings are matched...

Just my $0.02...

I forgot to mention, I use Pure Direct mode. Which of course sounds different than Stereo mode with tone controls flat and YPAO off.

The larger point is that this is a simple experiment that many can try at home. I find the with the 4 ohm setting sound become less dynamic. Folks tend to talk about distortion and its audibility and not about compression and there are measurements out there showing the behavior of amplifiers when they clip. Clipping in some amps is more objectionable than others.

Amps clip more often than people think and when they do, the louder sounds are not produced (often bass) but other, usually higher frequencies continue to be amplified. This changes the balance.

- Rich

 

[Irvrobinson]

My amps clip more often than people think and when they do, the louder sounds are not produced (often bass) but other, usually higher frequencies continue to be amplified. This changes the balance.

- Rich

I fixed that for ya. Mr. Salon driver blower. For the rest of us, not so much. ;-)

 

[RichB]

I fixed that for ya. Mr. Salon driver blower. For the rest of us, not so much. ;-)

Rascal. Hey, those midranges were defective, I tell you.

These days I am not taxing my amps much.
I've taken in my 88 year old mother and entered hearing preservation mode.

- Rich

 

[PENG]

Perhaps other can weigh in here but here are some measurements taken of a SS 300 WPC amplifier that is available now. Stereophile uses two tone tests and perhaps that is unfair but at 100WPC there are multiple harmonics in the -35 DB range. At 1 watt the harmonics are much better at about -62 DB.

It is fair to say that this is a stress test but playing complex tones (music) could not these distortion for some amplifiers be much higher than measured using pure tones?

SS amplifiers tend to be more rigorously measured than AVR amplifiers, so I don't think there is comparable data.

- Rich

If you use a complex wave that has more than one fundamental frequency then it is going to have more harmonic distortions because a non sinusoidal wave is made up of an infinite series of harmonics. A pure tone is a pure tone, and is sinusoidal by definition, of just one single fundamental frequency so the harmonic distortions will be limited to the frequencies in multiples of that one single fundamental frequency only. I would not consider using complex tones like music signals is a stress test. Audio amps are designed to amplify such signal after all.

 

[PENG]

I forgot to mention, I use Pure Direct mode. Which of course sounds different than Stereo mode with tone controls flat and YPAO off.

The larger point is that this is a simple experiment that many can try at home. I find the with the 4 ohm setting sound become less dynamic. Folks tend to talk about distortion and its audibility and not about compression and there are measurements out there showing the behavior of amplifiers when they clip. Clipping in some amps is more objectionable than others.

Amps clip more often than people think and when they do, the louder sounds are not produced (often bass) but other, usually higher frequencies continue to be amplified. This changes the balance.

- Rich

That is obvious, Gene has emphasized the benefit of sticking to the 8 ohm setting more than once already. If you use the 4 ohm setting, most likely the amp will then reduce the rail voltage, effectively rendering the amp less powerful. A 100 W 8 ohm rated amp may then become 75 W 4 ohm, or even lower rated effectively, no wonder you sensed the loss of dynamics.

 

[PENG]

I don't think so.

I think the majority of the 61% voters think that all amps sound different no matter what the condition is.

I think the majority of the 61% voters think that all amps have a sound signature of their own.

I think the truth may lie in between. Some may actually voted yes because of the "caveats" and some, perhaps more voted yes for reason you cited. There is no way of knowing for sure, without doing another poll on the rationale.

 

[RichB]

That is obvious, Gene has emphasized the benefit of sticking to the 8 ohm setting more than once already. If you use the 4 ohm setting, most likely the amp will then reduce the rail voltage, effectively rendering the amp less powerful. A 100 W 8 ohm rated amp may then become 75 W 4 ohm, or even lower rated effectively, no wonder you sensed the loss of dynamics.

I agree, it is both obvious and easily demonstrated in any system with an AVR with a 4 ohm setting.

These discussions usually center around clipping distortion but amplitude deficiencies and changes in tonal balance are also recognizable when amplifier power is insufficient.

- Rich

 

[mtrycrafts]

I recall that part too.

My take-away oversimplified message from TAC was that at the end of the day, comparing apples to apples under the same exact conditions, all amps regardless of type (A, AB, H, D, etc.) sound the same because they don't have a sound signature of their own. The same goes for cables/wires, preamps, DACs, CD players.

Back in their day class D amps were not in consumerland. He looked at the different approach in transistor type circuits, etc mostly. Of course, they didn't go into clipping on one amp to see if that is audibly different and so on. And, if there was something David was certainly capable of troubleshooting an amp.
They still have a number of the issues available to to download or read online if someone is interested.