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Low distortion in AVR vs sound quality

reg19

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Does low distortion automatically imply better, more desired sound quality? Or is the following figure not in that context?

THD is junk.png
 

ruinevil

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Per Geddes, it depends on the source and type of distortion. Distortion in electronics is much more audible than distortion in the speaker/room/headphone. IMD is more audible than THD. Last line makes sense. I would even say, you could have speaker/room/headphone distortion above above audibility threshold and still not hear it.
 

Gedeon

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Dynamics is also a factor which plays a big role and it seems difficult to measure. Some amps claims to be able to deliver 100w while others also claim those 100w, however not all A/B amplifiers are equally designed and not all have the same capacitors size.

Slew rate, peak amperes, and damping factor can also be taken in account but I haven't found reviews which measure those (or I'm unable to extract that info for the reviews), and their audible impact (if any).
 

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Dynamics is also a factor which plays a big role and it seems difficult to measure. Some amps claims to be able to deliver 100w while others also claim those 100w, however not all A/B amplifiers are equally designed and not all have the same capacitors size.

Slew rate, peak amperes, and damping factor can also be taken in account but I haven't found reviews which measure those (or I'm unable to extract that info for the reviews), and their audible impact (if any).

Agreed. + Once peak max output is reached, how the amplifier recovers from clipping completely changes its sound. This was one of the reasons valve amps often subjectively sound good, because when driven into clipping, they often just produce 2nd order harmonics, and little else. Which actually sounds quite nice. Vs a old SS amp that sounds horrendous, and recovers over seconds rather than milliseconds.

84db/1 w speakers can need LOTS of power, especially if they start dynamically compressing.

As for low distortion within the power limits of the amp, for me the top performing (Denon x3600) would barely meet the criteria for inaudible distortion with any kind of safety margin I would expect.

I don't like the use of linear phase FIR filters for EQ in AVRs as a rule of thumb either (which as I understand it most if not all are) but that's another story.
 
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reg19

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Dynamics is also a factor which plays a big role and it seems difficult to measure. Some amps claims to be able to deliver 100w while others also claim those 100w, however not all A/B amplifiers are equally designed and not all have the same capacitors size.

Slew rate, peak amperes, and damping factor can also be taken in account but I haven't found reviews which measure those (or I'm unable to extract that info for the reviews), and their audible impact (if any).

Click on this to see a study on why tube sounds better than SS

Here is a similar explanation that also adds the clipping differences

Here is PS Audio's take on it

Question is not tubes vs SS but why certain amps sound good. Given what we know about tubes vs SS, does this change what we search for in our measurements?
 

Lbstyling

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Click on this to see a study on why tube sounds better than SS

Here is a similar explanation that also adds the clipping differences

Here is PS Audio's take on it

Question is not tubes vs SS but why certain amps sound good. Given what we know about tubes vs SS, does this change what we search for in our measurements?

Although the knowledge of what the audiable differences are is valuable, in This day and age, I would suggest we can generally just throw the required power at it and make the problem moot by choosing an amp with 3-6 dB of headroom over target peak SPL.
 

RichB

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For the most part, amps are measured steady state. They are note measured into reactive loads (like speakers). Distortion can dramatically increase when driving a load. Amps with high output impedance will have output deviating from linearity with the changing load.

Tubes have higher output impedance than SS so with change the levels of playback for different frequencies. This is not traditionally considered distortion but it should be (IMO). Preferences are fine. My personal choices is to aim for neutrality (and linearity) in all components.

- Rich
 
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peng

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For the most part, amps are measured steady state. They are note measured into reactive loads (like speakers). Distortion can dramatically increase when driving a load. Amps with high output impedance will output, deviating from linearity, with the changing load.

Tubes have higher output impedance than SS so with change the levels of playback for different frequencies. This is not traditionally considered distortion but it should be (IMO). Preferences are fine. My personal choices is to aim for neutrality (and linearity) in all components.

- Rich

May be we can convince Amir to pick a speaker and use it to compare amps and AVR distortions, using the AHB2 as reference because it currently ranks top on the chart.:D May be pick a speaker that is not too hard to drive but not the easiest load either, something like Revel's, and preferably 4 ohm rated. You and I both have done something like that using REW, Omni mic for you and Umik-1 for me, but I think Amir can do the same with much better consistency and accuracy. Do you think it is something worth doing, or the results won't tell us anything?
 

RichB

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May be we can convince Amir to pick a speaker and use it to compare amps and AVR distortions, using the AHB2 as reference because it currently ranks top on the chart.:D May be pick a speaker that is not too hard to drive but not the easiest load either, something like Revel's, and preferably 4 ohm rated. You and I both have done something like that using REW, Omni mic for you and Umik-1 for me, but I think Amir can do the same with much better consistency and accuracy. Do you think it is something worth doing, or the results won't tell us anything?

I think @amirm mentioned a project to make a simulated speaker similar to Stereophile. That could be useful if applied consistently. But there is a controversy if made too demanding. Is phase +/- 45 degrees and 3.5 Ohms a good number? Maybe, but that might cause problems with some amps but a persons speakers are far more benign, would I care? Should I pay extra?

I have listened to AVR amps in the past and found them lacking driving the Salon2s at very modest listening levels, I did not measure but I assume in the mid 80 dB range. I have heard Class-G amps that sounded really good at low levels but did not care for them when turned up.

For each, it is a matter of selecting the quality and performance that matches their habits and system. I have listened to Sunfire Cinema Grand, Outlaw 7200, M2200 (older version), 7500, Parasound A21, A31, A51, ATI AT3000, AT4000, AT6000 and now Benchmark AHB2 and formed certain opinions. While I do feet the AHB2s have more apparent detail, the size, weight and heat also contributed to their selection. Plus, I really like superbly engineered products.

I don't know if the current gear can do a burst test and measure all aspects, amplitude, phase, and distortion during a barrage of on-off tones that might be a bit more like music. It seems like amp designers have different goals but seem to have the tools to achieve them.

- Rich
 
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Lbstyling

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I think @amirm mentioned a project to make a simulated speaker similar to Stereophile. That could be useful if applied consistently. But there is a controversy if made too demanding. Is phase +/- 45 degrees and 3.5 Ohms a good number. Maybe but that might cause problems with some amps but if my speakers are far more benign, would I care? Should I pay extra?

I have listened to AVR amps in the past and found them lacking driving the Salon2s at very modest listening levels, I did not measure but I assume in the mid 80 dB range. I have heard Class-G amps that sounded really good at low levels but did not care for them when turned up.

For each, it is a matter of selecting the quality and performance that matches their habits and system. I have listened to Sunfire Cinema Grand, Outlaw 7200, M2200 (older version), 7500, Parasound A21, A31, A51, ATI AT3000, AT4000, AT6000 and now Benchmark AHB2 and formed certain opinions. While I do feet the AHB2s have more apparent detail, the size, weight and heat also contributed to their selection. Plus, I really like superbly engineered products.

I don't know if the current gear can do a burst test and measure all aspects, amplitude, phase, and distortion during a barrage of on-off tones that might be a bit more like music. It seems like amp designers have different goals but seem to have the tools to achieve them.

- Rich

Salon 2's are 86.4db/1w.

That's 101.4 db at 32w.

Unless there is a severe impedance dip, almost any AVR will barely even warm up at 90db into this speaker.

I would imagine power was not the cause of the sound differences you heard.

Distortion in its many forms including ground loops, mains hum etc or EQ filters are your likely culprits.

After listening to the Bruno Putzeys interview on Jonnie Darkos podcast, there is so much you have to get right with earthing (between pre and power or usb from pc etc) before an amp performs as it measures under test conditions that I would guess very few systems out in the wild perform as they are designed anyway!
 

RichB

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Salon 2's are 86.4db/1w.

That's 101.4 db at 32w.

Unless there is a severe impedance dip, almost any AVR will barely even warm up at 90db into this speaker.

I would imagine power was not the cause of the sound differences you heard.

Distortion in its many forms including ground loops, mains hum etc or EQ filters are your likely culprits.

After listening to the Bruno Putzeys interview on Jonnie Darkos podcast, there is so much you have to get right with earthing (between pre and power or usb from pc etc) before an amp performs as it measures under test conditions that I would guess very few systems out in the wild perform as they are designed anyway!

After reading one of his interviews, it is clear that he is both clever and colorful. I have to say the description of class-D wanting to anything but amplify including catch fire, I am a bit put off on the technology, especially in a must work vacation home.

- Rich
 

Foxxy

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Does low distortion automatically imply better, more desired sound quality? Or is the following figure not in that context?

View attachment 76291
The last line makes my head hurt. Because that depends on the playback level.
Also look at those levels! 10% THD, 20% THD? This is all various grades of garbage, of course the makeup of that is hugely important. Just look at speakers.
You never want any unwanted component in the sound to go above 0.1%. And even then it's not 100%. AES tests established 0.01% as the solid value for audio transparency.

It's nice they seemingly found a way to quantisise the objectionability of noise makeup but to what end? I mean, it's been tested in the past that e.g. tubes can put out a lot more distortion before we even notice because the makeup is so nice. So we can now put a new number on it. But as I said, if you have a solid state with a distortion of 1% before we even start clipping, it's garbage anyway.

Wanna know how 10%TD (total distortion, THD+IMD) sounds? In the worst possible makeup? Completely disharmonic?
http://ethanwiner.com/audibility.html
Get the concerto-40 file and listen in.
Now imagine this being in your music, all the time. Fortunately not even intermodulation sounds that jarring but eh, also very nasty.
concerto-50 is 3.15%TD, concerto-60 is 1%TD. Finally, concerto-7 represents 0.316%TD.
Note that this is also a fixed level so unlike normal distortion components which vary with the level of the musical content this one is always loud.

Have fun, see how subtle you can hear and if you have multiple audio playback devices, see on which you can go the lowest :)
 

MerlinGS

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Salon 2's are 86.4db/1w.
That's 101.4 db at 32w.
Unless there is a severe impedance dip, almost any AVR will barely even warm up at 90db into this speaker.
I would imagine power was not the cause of the sound differences you heard.
Even assuming a speaker is a "benign" load, your assumptions are incorrect regarding power. Unless the speaker is a line source (which the Salon 2 is not), the sound level will reduce by 6 decibel for every doubling of distance; i.e. 101 db at 1 meter, 95 at two meters, 89 at 4 meters. If you are listening to classical music at sit at 12ft you are getting ~92 db peaks. I doubt the Salon 2s present a purely resistive load. If you a decent size room and you like to listen to rock or jazz with some loudness then 64w would clearly be insufficient (arguably 128 would be insufficient, and for some 256w would be insufficient). If you like to listen to orchestral pieces with decent dynamic range, 256 would be insufficient for many in a decent size room. So, whether power was the cause, it depends on the type of music, room size, listening distance and type of load, just to name a few factors (e.g. as @RichB already noted tubes have higher output impedance than SS, and this discrepancy can affect how a tube amp sounds, single ended tube amps are basically amps with unpredictable (because it is defined by the speaker's impedance) eq)
 

RichB

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Even assuming a speaker is a "benign" load, your assumptions are incorrect regarding power. Unless the speaker is a line source (which the Salon 2 is not), the sound level will reduce by 6 decibel for every doubling of distance; i.e. 101 db at 1 meter, 95 at two meters, 89 at 4 meters. If you are listening to classical music at sit at 12ft you are getting ~92 db peaks. I doubt the Salon 2s present a purely resistive load. If you a decent size room and you like to listen to rock or jazz with some loudness then 64w would clearly be insufficient (arguably 128 would be insufficient, and for some 256w would be insufficient). If you like to listen to orchestral pieces with decent dynamic range, 256 would be insufficient for many in a decent size room. So, whether power was the cause, it depends on the type of music, room size, listening distance and type of load, just to name a few factors (e.g. as @RichB already noted tubes have higher output impedance than SS, and this discrepancy can affect how a tube amp sounds, single ended tube amps are basically amps with unpredictable (because it is defined by the speaker's impedance) eq)

My seating position is 11 feet in a 15 x 30 x 10 foot room. I found that in stereo mode room gain made up for the distance loss, so 1 watt provided 86 dB. I did these measurements to explain why I never clip the Benchmark AHB2s (180 Watts @ 4 Ohms). Not that folks can and will use more power but I don't which was a surprise. As a result, I bi-amp though the option to bridge is always avaiable.

- Rich
 

peng

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I came across a good read on power amps a long time ago but couldn't find it until now.
https://sound-au.com/amp_design.htm#s5

It is a long one, but sect. 5 Measurements Versus Subjectivity sounded interesting so I am quoting it below:

"If I never hear someone complaining that "distortion measurements are invalid, and a waste of time" again, it will be too soon. I am so fed up with self-proclaimed experts (where 'x' is an unknown quantity, and a 'spurt' is a drip under pressure) claiming that 'real world' signals are so much more complicated than a sinewave, and that static distortion measurements are completely meaningless. Likewise, some complain that sinewaves are 'too simple', and that somehow they fail to stress an amplifier as much as music will.
Measurements are not meaningless, and real world signals are sinewaves! The only difference is that with music, there is usually a large number of sinewaves, all added together. There is not a myriad of simultaneous signals passing through an amp, just one (for a single channel, naturally).
Since physics tells us that no two masses can occupy the same physical space at the same time, so it is with voltages and currents. There can only ever be one value of voltage and one value of current flowing through a single circuit element at any instant of time - if it were any different, the concept of digital recording could never exist, since in a digital recording the instantaneous voltage is sampled and digitised at the sampling rate. This would clearly be impossible if there were say 3 different voltages all present simultaneously.
So, how do these x-spurts determine if an amplifier has a tiny bit of crossover distortion (for example). I can see it as the residual from my distortion meter, and it is instantly recognisable for what it really is, and I can see the difference when I make a change to a circuit to correct the problem. If I had to rely on my ears (which although getting older, still work quite well), It would take me much longer to identify the problem, and even longer to be certain that it was gone. I'm not talking about the really gross crossover distortion that one gets from an under-biased amp, I am referring to vestiges - miniscule amounts that will barely register on the meter - I use my oscilloscope to see the exact distortion waveform. I suspect that this dilemma is 'solved' by some by simply not using the push-pull arrangement at all, thereby ensuring that power is severely limited, and other distortion is so high that they would not dare to publish the results.
These same x-spurts may wax lyrical about some really grotty single ended triode amp, with no power and a highly questionable output transformer, limited frequency response and a damping factor of unity if it is lucky.
Don't get me wrong - I'm not saying that this is a definition of single-ended triode amps (for example), there are some which I am sure sound very nice - not my cup of tea, but 'nice'. I have seen circuits published on the web that I would not use to drive a clock radio speaker (no names, so don't ask), and 'testimonials' from people who have purchased this rubbish, but there are undoubtedly some that do use quality components and probably sound ok at low volume levels.
Sorry if I sound vehement (vitriolic, even), but quite frankly this p****s me off badly. There are so many people waving their 'knowledge' about, and many of them are either pandering to the Magic Market, or talking through their hats.
The whole idea of taking measurements is to ensure that the product meets some quality standard. Once this standard is removed and we are expected to let our ears be the judge, how are we supposed to know if we got what we paid for? If the product turns out to sound 'bad', should we accept this, or perhaps we should listen to it for long enough that we get used to the sound (this will happen - eventually - it's called 'burn-in' by the subjectivists). I am not willing to accept this, and I know that many others feel the same.
Please don't think that I am advocating specsmanship, because I'm not. I just happen to think that consumers are entitled to some minimum performance standard that the equipment should meet (or exceed). I have yet to hear any amplifier with high distortion levels and/or limited bandwidth sound better than a similar amplifier with lower distortion and wider bandwidth. This implies that we compare like with like - a comparison between a nice valve amp and a nasty transistor amp will still show the transistor amp as having better specs, but we can be assured that it will sound worse. In similar vein, a nice transistor amp compared against a rather poor valve amp may cause some confusion, often due to low damping from the valve amp which makes it easy to imagine that it sounds 'better'.
We need measurements, because they tell us about the things that we often either can't hear, or that may be audible in a way that confuses our senses. Listening tests are also necessary, but they must be properly conducted as a true blind A-B test or the results are meaningless. Sighted tests (where you know exactly which piece of gear you are listening to) are fatally flawed and will almost always provide the expected outcome.
"
 

RichB

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I came across a good read on power amps a long time ago but couldn't find it until now.
https://sound-au.com/amp_design.htm#s5

It is a long one, but sect. 5 Measurements Versus Subjectivity sounded interesting so I am quoting it below:

"If I never hear someone complaining that "distortion measurements are invalid, and a waste of time" again, it will be too soon. I am so fed up with self-proclaimed experts (where 'x' is an unknown quantity, and a 'spurt' is a drip under pressure) claiming that 'real world' signals are so much more complicated than a sinewave, and that static distortion measurements are completely meaningless. Likewise, some complain that sinewaves are 'too simple', and that somehow they fail to stress an amplifier as much as music will.
Measurements are not meaningless, and real world signals are sinewaves! The only difference is that with music, there is usually a large number of sinewaves, all added together. There is not a myriad of simultaneous signals passing through an amp, just one (for a single channel, naturally).
Since physics tells us that no two masses can occupy the same physical space at the same time, so it is with voltages and currents. There can only ever be one value of voltage and one value of current flowing through a single circuit element at any instant of time - if it were any different, the concept of digital recording could never exist, since in a digital recording the instantaneous voltage is sampled and digitised at the sampling rate. This would clearly be impossible if there were say 3 different voltages all present simultaneously.
So, how do these x-spurts determine if an amplifier has a tiny bit of crossover distortion (for example). I can see it as the residual from my distortion meter, and it is instantly recognisable for what it really is, and I can see the difference when I make a change to a circuit to correct the problem. If I had to rely on my ears (which although getting older, still work quite well), It would take me much longer to identify the problem, and even longer to be certain that it was gone. I'm not talking about the really gross crossover distortion that one gets from an under-biased amp, I am referring to vestiges - miniscule amounts that will barely register on the meter - I use my oscilloscope to see the exact distortion waveform. I suspect that this dilemma is 'solved' by some by simply not using the push-pull arrangement at all, thereby ensuring that power is severely limited, and other distortion is so high that they would not dare to publish the results.
These same x-spurts may wax lyrical about some really grotty single ended triode amp, with no power and a highly questionable output transformer, limited frequency response and a damping factor of unity if it is lucky.
Don't get me wrong - I'm not saying that this is a definition of single-ended triode amps (for example), there are some which I am sure sound very nice - not my cup of tea, but 'nice'. I have seen circuits published on the web that I would not use to drive a clock radio speaker (no names, so don't ask), and 'testimonials' from people who have purchased this rubbish, but there are undoubtedly some that do use quality components and probably sound ok at low volume levels.
Sorry if I sound vehement (vitriolic, even), but quite frankly this p****s me off badly. There are so many people waving their 'knowledge' about, and many of them are either pandering to the Magic Market, or talking through their hats.
The whole idea of taking measurements is to ensure that the product meets some quality standard. Once this standard is removed and we are expected to let our ears be the judge, how are we supposed to know if we got what we paid for? If the product turns out to sound 'bad', should we accept this, or perhaps we should listen to it for long enough that we get used to the sound (this will happen - eventually - it's called 'burn-in' by the subjectivists). I am not willing to accept this, and I know that many others feel the same.
Please don't think that I am advocating specsmanship, because I'm not. I just happen to think that consumers are entitled to some minimum performance standard that the equipment should meet (or exceed). I have yet to hear any amplifier with high distortion levels and/or limited bandwidth sound better than a similar amplifier with lower distortion and wider bandwidth. This implies that we compare like with like - a comparison between a nice valve amp and a nasty transistor amp will still show the transistor amp as having better specs, but we can be assured that it will sound worse. In similar vein, a nice transistor amp compared against a rather poor valve amp may cause some confusion, often due to low damping from the valve amp which makes it easy to imagine that it sounds 'better'.
We need measurements, because they tell us about the things that we often either can't hear, or that may be audible in a way that confuses our senses. Listening tests are also necessary, but they must be properly conducted as a true blind A-B test or the results are meaningless. Sighted tests (where you know exactly which piece of gear you are listening to) are fatally flawed and will almost always provide the expected outcome.
"

On ASR, I think the pure subjectivist is not encouraged.
I subscribe to the notion that, generally, better measuring products sound better. The argument then becomes at what level does distortion become audible. This has been discussed many times. We know that 0 SPL is the absolute level of inaudibility. For me, it is the probably in 15 dB SPL at low volume between .1 and 1 watt is the target.

That said, I have purchased a streaming device for Roon that measured extremely well in DAC mode. I voltage level-matched and created a zone for the streamer and the Oppo UDP-205 with Roon and found the Oppo to be superior. Cymbals sounded better defined. There is a complex chain so it may not have been the streamer, but this is my configuration so this is my personal acceptance test. In a different use case, the SINAD measurement was not, subjectively, indicative.

P.S. I will not mention the steamer brand because it was a short test and performed limited testing, so it would be unfair.

- Rich
 

lashto

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Does low distortion automatically imply better, more desired sound quality? Or is the following figure not in that context?

View attachment 76291
that is a very nice screenshot, particularly happy that it matches ~all my "HD rambling" around ASR. I would only disagree partially with the last point: good chances that it is true but AFAIK it's only an untested "maybe".

And a short answer to your questions.
Generally, better THD translates into what people describe as cleaner/clearer sound. That is both better and desired.
Depending on the HD spectrum (i.e. the kind of HD), that clean/clear sound might be anywhere between warm/musical or cold/analytical. This is all desire/preference territory: some people prefer warm, some people prefer analytical, some do not care, some hate both...
 

Lbstyling

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The last line makes my head hurt. Because that depends on the playback level.
Also look at those levels! 10% THD, 20% THD? This is all various grades of garbage, of course the makeup of that is hugely important. Just look at speakers.
You never want any unwanted component in the sound to go above 0.1%. And even then it's not 100%. AES tests established 0.01% as the solid value for audio transparency.

Not that I doubt distortions of some forms are audible below 0.1%, but do you have a link to this study?
 

peng

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On ASR, I think the pure subjectivist is not encouraged.

In my opinion that is more so the case on Audioholics.com. On ASR, it seems more like a 50/50 split.
 
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