Audible differences between 2-channel s/s amps and AVRs, when operated below clipping? - AVS Forum
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post #1 of 127 Old 07-09-2013, 04:51 PM - Thread Starter
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Per a thread in the speaker subforum, member BufordTJustice claims that amps such as Emotiva sound better than the amps in AVRs, even when both are operated in their linear region, below clipping.

See thread here for background:
http://www.avsforum.com/t/1480699/receiver-recommend-for-ascend-cmt340ses-and-rythmik-12

I am bringing the thread to this subforum so as not to continue the off-topic discussion in that thread.

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post #2 of 127 Old 07-09-2013, 04:53 PM - Thread Starter
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Despite my attempt to move the discussion here, Buford continued to post in that thread.

For reference, here is his last post in that thread:

"The Emotiva I cited and recommended (UPA-500) is actually rated for lower wattage output levels than most of the AVR's rec'd (like the Denon 2313). Being that the UPA has a toroidal power supply transformer and the Denon has a laminated core transformer and that they are roughly the same weight, this means that we can infer that the UPA has a transformer with a higher VA rating and the ability to more efficiently pass current to the loudspeaker due the toroidal transformer (since the transformer is the heaviest component of a class A/B amplifier). A toroidal transformer of the same mass as a laminated core will always have a higher VA rating unless there has been a design error because toroidals are more efficient. So, it is highly likely that the UPA's power supply can pass current more efficiently than the Denon despite having an inferior wattage rating (which could be due to the number and type of output devices, power supply caps, among other things). Also, while having inferior rated wattage output, you can't tell me that the damping factors are identical between the two....which has a direct bearing on bass presentation as the amp interplays with the voice coils in the loudspeaker.

So, is it really that preposterous to think that they may sound different when both amps are not clipping within the context of the original post? I say no, it is not unreasonable to say that it is possible an observable difference could exist even if the limits of either amplifier are never reached."

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post #3 of 127 Old 07-09-2013, 04:56 PM
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And I last said:

"So, is it really that preposterous to think that they may sound different when both amps are not clipping within the context of the original post? I say no, it is not unreasonable to say that it is possible an observable difference could exist even if the limits of either amplifier are never reached."

The original context was when I recommended an Emotiva UPA-500 to be paired with a cheaper AVR as having optimum sound quality at all volume levels (and value) over a slightly more expensive AVR like the Denon 2313 to the OP of the linked thread.

Beave called the external amplifier a waste.

Here we are.

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post #4 of 127 Old 07-09-2013, 04:59 PM
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And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

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post #5 of 127 Old 07-09-2013, 04:59 PM - Thread Starter
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Quote:
Originally Posted by beaveav View Post

Despite my attempt to move the discussion here, Buford continued to post in that thread.

For reference, here is his last post in that thread:

"The Emotiva I cited and recommended (UPA-500) is actually rated for lower wattage output levels than most of the AVR's rec'd (like the Denon 2313). Being that the UPA has a toroidal power supply transformer and the Denon has a laminated core transformer and that they are roughly the same weight, this means that we can infer that the UPA has a transformer with a higher VA rating and the ability to more efficiently pass current to the loudspeaker due the toroidal transformer (since the transformer is the heaviest component of a class A/B amplifier). A toroidal transformer of the same mass as a laminated core will always have a higher VA rating unless there has been a design error because toroidals are more efficient. So, it is highly likely that the UPA's power supply can pass current more efficiently than the Denon despite having an inferior wattage rating (which could be due to the number and type of output devices, power supply caps, among other things). Also, while having inferior rated wattage output, you can't tell me that the damping factors are identical between the two....which has a direct bearing on bass presentation as the amp interplays with the voice coils in the loudspeaker.

So, is it really that preposterous to think that they may sound different when both amps are not clipping within the context of the original post? I say no, it is not unreasonable to say that it is possible an observable difference could exist even if the limits of either amplifier are never reached."

First, both amps have sufficiently high damping factors as to be below audibility. There was a discussion in this subforum about that very topic just in the last few days. Damping factor can be an issue with tube amps, which tend to have high output impedances, but with modern day solid state amps, damping factor is sufficiently high to not be an issue.

See this thread for info: http://www.avsforum.com/t/1479753/emotiva-xpr-1-vs-bryston-28b-sst2-anyone-ever-compare-these

Second, for the example you gave of the Denon vs the Emotiva, the Denon may have a higher power rating at 8 Ohms, but might not be able to keep up with the Emotiva at, say, a 4 Ohm load, or a 2 Ohm load. The Denon may go into shut-down (self protection mode) quicker than the Emotiva. Once again, that is a separate issue from what you claimed, yet it is about the fifth time you have brought it up.

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post #6 of 127 Old 07-09-2013, 05:01 PM - Thread Starter
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Quote:
Originally Posted by BufordTJustice View Post

And I last said:

"So, is it really that preposterous to think that they may sound different when both amps are not clipping within the context of the original post? I say no, it is not unreasonable to say that it is possible an observable difference could exist even if the limits of either amplifier are never reached."

The original context was when I recommended an Emotiva UPA-500 to be paired with a cheaper AVR as having optimum sound quality at all volume levels (and value) over a slightly more expensive AVR like the Denon 2313 to the OP of the linked thread.

Beave called the external amplifier a waste.

Here we are.

Please cite where I called the external amplifier a waste. Thanks in advance.

Next, please understand the topic: You claimed the external amp will sound better at all listening levels. I challenged that assertion. That is the topic at hand.

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post #7 of 127 Old 07-09-2013, 05:02 PM - Thread Starter
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Quote:
Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

I'm quite aware of what damping factor is. I've measured output impedance on countless audio devices as part of my past job. Now, show me a legitimate source that says damping factor makes an audible difference in modern solid-state amplifier designs.

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post #8 of 127 Old 07-09-2013, 05:44 PM
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Quote:
Originally Posted by beaveav View Post

Quote:
Originally Posted by BufordTJustice View Post

And I last said:

"So, is it really that preposterous to think that they may sound different when both amps are not clipping within the context of the original post? I say no, it is not unreasonable to say that it is possible an observable difference could exist even if the limits of either amplifier are never reached."

The original context was when I recommended an Emotiva UPA-500 to be paired with a cheaper AVR as having optimum sound quality at all volume levels (and value) over a slightly more expensive AVR like the Denon 2313 to the OP of the linked thread.

Beave called the external amplifier a waste.

Here we are.

Please cite where I called the external amplifier a waste. Thanks in advance.

Next, please understand the topic: You claimed the external amp will sound better at all listening levels. I challenged that assertion. That is the topic at hand.

Your implication was that for the purposes of increased sound quality below clipping, an external amp was unnecessary. I didn't place "waste" in quotes because it was not a quote.

Post # 11:

"Increased fidelity at all volume levels? As ArnyK would say, that's an audiophile myth. Just not true."

Post # 22:

"So, tell me again, what is your claim? Because you keep changing it. Yeah, a 22lb amp might have more current delivery capability than a 22lb receiver. So what? You claimed that the 22lb amp would sound better at all levels, didn't you? The increased current delivery capability would only come into play at high levels."


These were both in response to my post (#10):

"EDIT: I'll add that the main benefit of an external amplifier is rarely increased volume output before amp clipping...it is increased fidelity at all volume levels. The differences between a receiver and external amplifier are usually most glaring at low to moderate output levels when listening to music. If somebody wants more volume output, then they need to invest in some high efficiency speakers as even a doubling of wattage output only makes negligible increase in perceived volume. The fidelity is why I'm making my rec for an external amp."

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post #9 of 127 Old 07-09-2013, 05:46 PM
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Quote:
Originally Posted by beaveav View Post

Quote:
Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

I'm quite aware of what damping factor is. I've measured output impedance on countless audio devices as part of my past job. Now, show me a legitimate source that says damping factor makes an audible difference in modern solid-state amplifier designs.

If you read the white paper, you would see that is exactly what it states.

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post #10 of 127 Old 07-09-2013, 06:23 PM
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You know, if all solid state amps were designed and manufactured identically, I would agree with you. But they are not.

Different power supply transformers, different windings, different transformer designs (Toroidal, E-I core, U-I core, etc.), different filter caps. Damping factors differ as do amounts of negative feedback used in the design of each amp. Loudspeaker impedance (and, thus damping factor of the amp) fluctuates with frequency and with the temperature of the voice coil (even with temp increases as small as 10-15 degrees F). The crossover distortion of the devices used in that particular amplifier (and the percentage of overlap).

The quality and brand of output transistors....all of these things affect the complex musical signal being sent to the loudspeakers.

So, to reiterate my original statement: yes, it is possible that two solid state amplifiers can sound different even when operated in their linear regions.

Further, it is also possible that the Emotiva I recommended (UPA-500) sounds better (i.e. different) than the series of ~$400-$500 AVRs that were thrown on the table.

Your assertion, Beave, is that if they are operated linearly and they have essentially equivalent RMS wattage ratings, then they will sound identical. Please correct me if this is not the assertion you intended to convey.

EDIT: I haven't even mentioned the ~ +/-5% (or worse) manufacturing tolerances that are in place for electronics such as amplifiers.

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post #11 of 127 Old 07-09-2013, 06:55 PM
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An Old school read....It appears that solid state amplifiers have never even measured the same, much less sounded the same:

http://www.ka-electronics.com/images/pdf/Leinonen_Otala_Curl_TIM_Measurement.pdf

John Curl weighs-in on TIM, DIM, slew rate, and a host of other issues (and we haven't even gotten to Op-Amps!!!)

http://www.diyaudio.com/forums/solid-state/41770-whats-your-reasoning-not-whats-your-belief-2.html#post483882


NOW, for a discussion of the wild variability (which is MEASURABLE) of Op-Amps.

http://www.sg-acoustics.ch/analogue_audio/ic_opamps/index.html

Lots of material there. Lots of different measurements. Shouldn't be any different, according to your hypothesis, correct? Solid state and operating linearly......

Mayhaps your presuppositions about my original recommendation were poorly founded?

Also to weigh-in, Walt Jung (who authored this treatise):

All 210 pages from Walt's chapter on Audio amps (with focuses on op-amps, among other things)
http://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch6_final_I.pdf

It would seem that this goal of "identical" and "same" in the consumer audio industry is both untruthful and possibly unachievable.

So, "Per a thread in the speaker subforum, member BufordTJustice claims that amps such as Emotiva sound better than the amps in AVRs, even when both are operated in their linear region, below clipping."..... Yes, I claim that. And, while I may be in the minority here at AVS, I'm surely not alone in my opinions.

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post #12 of 127 Old 07-09-2013, 07:47 PM
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Quote:
Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

"Damping factor" is often thrown about as an important amplifier characteristic...and it is, to a point. The damping factor stated in a manufacturers spec sheet is not the same as the actual overall damping factor with loudspeakers connected. In fact, once you get above a damping factor of 20 or so, there is little to no difference in " actual damping factor". It's explained in more detail here:
http://www.roger-russell.com/wire/dampaugs.htm
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post #13 of 127 Old 07-09-2013, 07:55 PM
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More good stuff. Doug Self on Power amplifier design:
http://www.sg-acoustics.ch/analogue_audio/power_amplifiers/pdf/audio_power_amp_design_comments.pdf

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post #14 of 127 Old 07-09-2013, 07:57 PM
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Quote:
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Quote:
Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

"Damping factor" is often thrown about as an important amplifier characteristic...and it is, to a point. The damping factor stated in a manufacturers spec sheet is not the same as the actual overall damping factor with loudspeakers connected. In fact, once you get above a damping factor of 20 or so, there is little to no difference in " actual damping factor". It's explained in more detail here:
http://www.roger-russell.com/wire/dampaugs.htm

I agree, but it fluctuates wildly in response to several variables, including frequency-specific impedance for a given loudspeaker, the temperature of the VC of that loudspeakers' drivers, etc. All of these work to make damping factor a variable that can become more audible as power input increases. Is it THE deciding factor? I agree with you that usually, no, it's not.

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Figure 2.1 shows the crossover network as it is seen by the loudspeaker. The amplifier and speaker leads no longer exist, as they were assumed from the beginning to have zero impedance. The crossover now appears as a simple parallel LC network, with resonance tuned to the crossover frequency. For those who know what this means, the implication is obvious. For the remainder, we have a parallel tuned circuit, and with ideal components (no losses), its impedance is infinite at resonance! That means that at resonance, there is no damping whatsoever, and the "damping factor" is ... zero!
At one octave, the impedance is nominally the same as the design impedance, so for an 8Ω speaker, the network impedance is also 8Ω one octave above and below Xf. This means that the driver sees a damping factor (DF) of one! And this with a perfect amplifier, and superconducting speaker leads. This is not only unexpected, but is potentially quite unsatisfactory, as there is little to damp the loudspeaker back-EMF, so allowing perhaps significant overshoot and undershoot, with inevitable "smearing" in the time domain. Transients will not be right, as the loudspeaker is still able to contribute a significant amount of its own "signature" to the reproduced sound.
http://sound.westhost.com/biamp-vs-passive.htm
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http://sound.westhost.com/amp-sound.htm

"Some writers have claimed that all amplifiers actually sound the same, and to some extent (comparing apples with apples) this is "proven" in double-blind listening tests. I am a great believer in this technique, but there are some differences that cannot be readily explained. An amp that is deemed "identical" to another in a test situation, may sound completely different in a normal listening environment. It is these differences that are the hardest to deal with, since we do not always measure some of the things that can have a big influence on the sound. "

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post #17 of 127 Old 07-10-2013, 12:42 AM
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This comparison is, in fact, relevant.

http://www.stereophile.com/content/carver-challenge-page-2

"Bob's test hookup would show much more than frequency response differences. In fact, one of his most interesting statements, for those of the "every amplifier is the same except for frequency response" school, was that varying frequency response between the 1.0 and the reference amp made up only about 25% of the significant differences. Relative phase shift, source impedances (damping factors)—in short, every electrical difference between the amplifiers—would produce a signal at that test point between the Plus output terminals. When the amplifier outputs were identical, in all respects, there would be total cancellation—a null—of the difference signal. Bob's goal was a 70dB null, or an 0.03% difference between the two amps."

http://www.stereophile.com/content/carver-challenge-page-4

"But, as we relaxed with a Sheffield jazz record, we thought we picked up a difference between the reference and the 1.0. With the reference, the low range of the guitar was a bit ill-defined; with the 1.0, you could "count the cycles." Granted, in this respect the 1.0 was better than the reference, but that was beside the point! We were looking for duplication.

Bob reached into his bag of tricks and dropped the output of the 1.0 from 500 watts below 30Hz, to a mere 65–100W. Believe it or not, even though we were listening at subdued levels, that did the trick: the 1.0 was now a bit muddy and ill-defined through its lower range, just like the reference.

More interesting, though, and disturbing, was that the soundstaging had now changed, and the two amps were no longer the same. It turned out that Bob had to go back and diddle some more, exhausting his 48-hour limit."


"Carver claims that the original, unmodified M1.0 amplifier had been designed to sound "the way he wanted it to." If, in fact, he could make it sound any way he wished, as seemed to be proven with his success in this experiment, why then did he elect to go with a typical mid-fi "solid-state sound" instead of emulating the sound of one of the best-sounding solid-state or tubed amplifiers on the market? There were, it turns out, some good reasons.

Bob admits that he is not sure himself about the audible effects of some of the parameters he juggled to match the transfer functions of his amp to that of our reference. Had he been using this trimming technique to produce a certain desired combination of sonic qualities, using only his ears to evaluate what was going on, the task would have been quite a bit more difficult and time-consuming, the results far less predictable. This, in fact, is what he did with the 1.0 amplifier, which in his opinion still sounds excellent on the loudspeakers with which it will most likely be used (if not on the loudspeakers we used).

Secondly, Bob had never before had a chance to listen critically to a "world-class" amplifier like the one we chose as our reference, and ended up admitting that there were things about its sound that he preferred to his own amp. He might, he averred, "do some things differently in future designs.""

Emphasis mine.

It would seem that each amplifier (even SS) is left with the unique and indelible imprint of its designer with regard to its sonic character. The clear implication is certainly anything but "all SS amps sound the same when not clipped".

-Bob Carver

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Originally Posted by beaveav View Post

Please cite where I called the external amplifier a waste. Thanks in advance.

Next, please understand the topic: You claimed the external amp will sound better at all listening levels. I challenged that assertion. That is the topic at hand.

There were people in that thread (I was one) who told the OP that based on several factors pertinent to his situation an external amplifier was not necessary. Nobody said an external amplifier was a waste. Sometimes an amplifier is necessary. Whether one particular brand is necessary over another is subjective, and the topic of this conversation. Again.

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post #19 of 127 Old 07-10-2013, 06:21 AM
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Quote:
Originally Posted by beaveav View Post

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Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

I'm quite aware of what damping factor is. I've measured output impedance on countless audio devices as part of my past job. Now, show me a legitimate source that says damping factor makes an audible difference in modern solid-state amplifier designs.

If you read the white paper, you would see that is exactly what it states.

Not really. Amplifier source impedance (which we can obfuscate and unnecessarily complexify) by bringing in the artifice of damping factor) can be an audible issue for switchmode and tubed amplifiers. You need to show us where the Crown paper says it is an issue for good modern SS amplfiers, which includes AVRs with class AB or G output stages.
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post #20 of 127 Old 07-10-2013, 06:31 AM
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This comparison is, in fact, relevant.

http://www.stereophile.com/content/carver-challenge-page-1

and

http://www.stereophile.com/content/carver-challenge-page-2

etc.

"Bob's test hookup would show much more than frequency response differences. In fact, one of his most interesting statements, for those of the "every amplifier is the same except for frequency response" school, was that varying frequency response between the 1.0 and the reference amp made up only about 25% of the significant differences. Relative phase shift, source impedances (damping factors)—in short, every electrical difference between the amplifiers—would produce a signal at that test point between the Plus output terminals. When the amplifier outputs were identical, in all respects, there would be total cancellation—a null—of the difference signal. Bob's goal was a 70dB null, or an 0.03% difference between the two amps."

Most salient parameter is right at the top of the article:

"(first) Published: Oct 11, 1985"

By definition no amplifier discussed in the article is modern. It has to be using nearly 30 year old technology simply because it existed in 1985. The percentage of well-designed SS power amps on the market and in use then was significantly less 30 years ago than it is now. But amps that were good by modern standards were readily available then. They were less dominant and generally cost more $$ per watt.

Carver's criteria is excessively strict from a modern psychoacoustic viewpoint. 0.03% difference is about the same a 0.03 db difference and it is well known and generally agreed that even 0.1 dB has a generous safety margin. The technology of modern psychoacoustics arguably became generally known in the early 1990s.

Finally, the article appears to be at least partially based on sighted evaluations. Expectations can easily explain all observations and there is no evidence of control of expectation biases.

It's Stereophile and its based on subjective evaluations that have holes in them large enough to drive a Kenworth through. Everybody who is surprised should find a pointed cap and a corner to sit in! ;-)
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post #21 of 127 Old 07-10-2013, 06:38 AM
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Originally Posted by BufordTJustice View Post

And a Crown WP on damping factor.

http://www.crownaudio.com/media/pdf/amps/136224.pdf

"Damping factor" is often thrown about as an important amplifier characteristic...and it is, to a point.

One component of amplifier damping factor is speaker impedance, so saying it is an amplifier characteristic is not exactly correct. The parameter that people are searching for is source impedance, which is indeed a characteristic of amplfiiers.

Similarly, THD is often said to be a characteristic of amplifiers but it is actually a somewhat limited means for characterizing the nonlinear distortion of amplifiers. Nonlinear distortion is the relevant amplifier characteristic.
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post #22 of 127 Old 07-10-2013, 06:41 AM
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http://sound.westhost.com/amp-sound.htm

"Some writers have claimed that all amplifiers actually sound the same, and to some extent (comparing apples with apples) this is "proven" in double-blind listening tests.

Most of those writers are critics of DBT.

They are arguably just fomenting an excluded-middle argument.

DBT advocates do not generally say categorically that all amplifiers sound the same or are the same.

What they do say is that most if not all good amplifiers that are properly used in real world audio systems with reasonable recordings have no audible effect on sound quality.
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post #23 of 127 Old 07-10-2013, 12:16 PM
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I've been reading this thread today from where it started in the Speaker subforum..............

Let me see if I got this right..........

Given the parameters/ construct of the thread heading here, there's no SIGNIFICANT difference between a midpriced AVR from Denon, Yamaha, Onkyo, etc. and a 2 channel power amp from one of the "big names" ( Classe, Mark Levinson, Bryston, Carver, etc.) in terms of audio quality............

Then, if you do not need the headroom that the power amps provide over the AVR's, why buy them?
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post #24 of 127 Old 07-10-2013, 01:26 PM
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IME in most domestic situations a modern flagship AVR has enough juice to drive most speakers even if they are rated at 4 ohms nominal impedance IF you drive only two channels.

 

Nevertheless, if the room is large, lets say more than 60m3 and you like to listen to music at high volume levels, an AVR may not be enough. IMO the main reason is the PSUs of modern AVRs are not what they use to be 10-15 years ago. Modern AVRs have all the bell and whistles but they tend to be anemic. You can verify that if you open any AVR and check the fuses current rating.

 

This fact sometimes justify the use of a separate power amplifier.

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^^ I use a Denon AVR-4311 for 5 channels, the front stage does drop down to 4 ohms. I've had no problems at all at reference levels and below in a large room, 12' seating distance. In the same place I've had Anthem MCA 20 and Krell monoblocks (loaners) for front L & R, and with very casual, uncontrolled testing I couldn't tell a difference. I do acknowledge that this doesn't mean there was no difference, but it certainly was convincing enough to determine that $18k wasn't justified. For a time I had an Onkyo TX-8050 2 channel @ 80w per channel and a pair of 4 ohm Polk LSi9 that in another very large room (28' x 21' x 25' ceilings) needed more power than the Onkyo could provide before I was satisfied. I'd say your last statement is spot on.

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IME in most domestic situations a modern flagship AVR has enough juice to drive most speakers even if they are rated at 4 ohms nominal impedance IF you drive only two channels.

What evidence do you have that modern AVRs have problems when:

(1) They are not flagship models
(2) More than 2 channels are driven
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post #27 of 127 Old 07-11-2013, 11:50 AM
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What evidence do you have that modern AVRs have problems when:

(1) They are not flagship models
(2) More than 2 channels are driven

HI Arny.

 

I didn't mention any problem with AVRs. I only referred to the fact PSUs are anemic in last model AVRs, perhaps with due exception of flaghip AVRs.

 

For instance my current Yamaha RX-A2010, rated  @ 2 x 140Watts/channel, 20-20000Hz, measured like this:

 

 

It is easy to figure this out if you open the amp and find the PSUs' fuse rating at 3.5 Ampere.

 

Suppose the fuse was selected with safety factor equal to 1.2. Then you have safe 2.8 ampere to work at 127Volts, which means 355.6 watts to share between all channels and pre/pro inside the AVR.

 

My calculations are 172.8Watts @ two channels driven simultaneously, 69Watts @ 5 channels and 50 Watts @ 7 channels.

 

And this is the second AVRs in Yamaha's Aventage series. 

 

Then I opened an entry level AVR and find a 1.5 fuse in the AVR rated at 90 Watts/channel and I started guessing what the manufacturer is trying to sell...

 

Yes, I know 8-10 Watts are enough to obtain more than 90dB in a small room in stereo mode, but what happens with dynamic peaks as high as 10-15dB in a large room using speakers with 86dB sensitivity at 4 ohms nominal impedance? You need POWER to follow music dynamics... Only a flagship AVR has the guts... or you need to buy a separate amp. 

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post #28 of 127 Old 07-11-2013, 03:48 PM - Thread Starter
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If you read the white paper, you would see that is exactly what it states.

Indeed it does. It does not, however, tell you at what point damping factor is audible and at what point it is not an audible issue. That's a very important piece of the puzzle, is it not?

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post #29 of 127 Old 07-11-2013, 03:53 PM - Thread Starter
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You know, if all solid state amps were designed and manufactured identically, I would agree with you. But they are not.

Different power supply transformers, different windings, different transformer designs (Toroidal, E-I core, U-I core, etc.), different filter caps. Damping factors differ as do amounts of negative feedback used in the design of each amp. Loudspeaker impedance (and, thus damping factor of the amp) fluctuates with frequency and with the temperature of the voice coil (even with temp increases as small as 10-15 degrees F). The crossover distortion of the devices used in that particular amplifier (and the percentage of overlap).

The quality and brand of output transistors....all of these things affect the complex musical signal being sent to the loudspeakers.

So, to reiterate my original statement: yes, it is possible that two solid state amplifiers can sound different even when operated in their linear regions.

Further, it is also possible that the Emotiva I recommended (UPA-500) sounds better (i.e. different) than the series of ~$400-$500 AVRs that were thrown on the table.

Your assertion, Beave, is that if they are operated linearly and they have essentially equivalent RMS wattage ratings, then they will sound identical. Please correct me if this is not the assertion you intended to convey.

EDIT: I haven't even mentioned the ~ +/-5% (or worse) manufacturing tolerances that are in place for electronics such as amplifiers.

There are countless ways to skin a cat, so to speak. An infinite variety of parts. Different resistors, caps, transistors, etc. Yes, we know that. I know it all too well, having gone over BOMs (bill of materials) for consumer electronics until I was blue in the face.

But guess what? If they all lead to an amp with flat frequency response, low SNR, and low THD, none of those things you mention will matter to the listener.

You might have one with an SNR of 96dB and another with an SNR of 98dB. You think that's audible?

You might have one with THD < 0.05% and another with THD < 0.02%. You think that is audible?

As for your assertion that amps use +/-5% parts, show me some data to back that up, and tell me where in the schematic the parts are located (because that's a critical issue). Parts in the power supply filtering can have more than that for a tolerance and still be fine. If the parts are in the signal path and are critical to output, would they not show up in freq resp measurements? So why do you never see any solid-state amps with a poor frequency response measurement in a magazine?
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post #30 of 127 Old 07-11-2013, 03:56 PM - Thread Starter
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Quote:
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An Old school read....It appears that solid state amplifiers have never even measured the same, much less sounded the same:

http://www.ka-electronics.com/images/pdf/Leinonen_Otala_Curl_TIM_Measurement.pdf

John Curl weighs-in on TIM, DIM, slew rate, and a host of other issues (and we haven't even gotten to Op-Amps!!!)

http://www.diyaudio.com/forums/solid-state/41770-whats-your-reasoning-not-whats-your-belief-2.html#post483882


NOW, for a discussion of the wild variability (which is MEASURABLE) of Op-Amps.

http://www.sg-acoustics.ch/analogue_audio/ic_opamps/index.html

Lots of material there. Lots of different measurements. Shouldn't be any different, according to your hypothesis, correct? Solid state and operating linearly......

Mayhaps your presuppositions about my original recommendation were poorly founded?

Also to weigh-in, Walt Jung (who authored this treatise):

All 210 pages from Walt's chapter on Audio amps (with focuses on op-amps, among other things)
http://www.analog.com/library/analogDialogue/archives/39-05/Web_Ch6_final_I.pdf

It would seem that this goal of "identical" and "same" in the consumer audio industry is both untruthful and possibly unachievable.

So, "Per a thread in the speaker subforum, member BufordTJustice claims that amps such as Emotiva sound better than the amps in AVRs, even when both are operated in their linear region, below clipping."..... Yes, I claim that. And, while I may be in the minority here at AVS, I'm surely not alone in my opinions.

1. First link is old, as Arny pointed out.
2. John Curl thinks he can hear differences from one resistor to another, but has never proved that in blind testing. He's a very smart guy, but even smart people can hold beliefs that they can't prove.
3. Having implemented countless op amps in consumer electronics, I'm well aware that they can and do have measurable differences. But as I stated before, they're well below audible thresholds, so who cares? And Arny has shown that you can string together multiple op amps in series before there is any audible degradation.
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