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).
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?
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. 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 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!
The last line makes my head hurt. Because that depends on the playback level.Does low distortion automatically imply better, more desired sound quality? Or is the following figure not in that context?
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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)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)
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."
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".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.
On ASR, I think the pure subjectivist is not encouraged.