Tubes, tone, and old age.

atmaspher

12-07-2023 at 02:09pm 

And on a related note, what measurements - if there are any - show the difference in sound between SS and tubes?

Could one see this on a frequency chart?

Yes. Look at distortion vs frequency- if it begins rising much below about 10KHz you will have a brightness problem since higher ordered harmonics will be higher than the THD suggests.

The other thing to look at is the distortion profile. Smoother sounding amps have a greater degree of 2nd and 3rd harmonic than amps that tend to sound bright and harsh. This is simply because the 2nd and 3rd in the latter amps is insufficient to mask the higher orders. Our ears interpret the higher orders as harsh and bright using the same metrics that cause tone color in musical instruments.

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Thanks that's very interesting.   So we can sort of measure these subtle differences but not really.  And is the binaural nature of hearing ever part of it?  The subtle phase differences of stereo?

The scientific method requires a theory followed by testing, with reliable results to prove the theory.  Without testing, measurements are not necessarily significant.  You need a real life A/B comparison.  

Yes. Look at distortion vs frequency- if it begins rising much below about 10KHz you will have a brightness problem since higher ordered harmonics will be higher than the THD suggests.

The other thing to look at is the distortion profile. Smoother sounding amps have a greater degree of 2nd and 3rd harmonic than amps that tend to sound bright and harsh. This is simply because the 2nd and 3rd in the latter amps is insufficient to mask the higher orders. Our ears interpret the higher orders as harsh and bright using the same metrics that cause tone color in musical instruments.

Ralph...this makes me want to if there is a level of distortion below which the increase in THD+N doesn't really matter as far as harshness is concerned? 

Some examples might be the Pass XA25 where THD+noise starts to rise at 300 hz but starts from a level of .0015 and then hits .01 by 5khz and .02 by 10khz.  Or, another example could be the Benchmark AHB2 where the increase doesn't start until 2khz and starts from .0004 and rises to .001...or the NAD 298 Purifi where the increase starts at 7khz and rises from .003 to .01.  (All from Stereophile measurements).

None of these amplifiers are usually described as harsh (although some feel the AHB2 or the NAD may be a little sterile)...and yet they all have increasing THD+noise starting below 10kz...and all are predominantly 3rd harmonic dominant.

So, is it possible that if the increasing THD+distortion starts below 10khz...but is at a low enough starting point and is predominantly 3rd harmonic, then the sound might not be harsh...or am I missing something else that could explain this?