Full detailed sound at 30 - 40 - 50 dB

Maybe the Schiit-heads next EQ (Loki Maxi?) will be balanced.

Exactly!

I mentioned that here: https://forum.audiogon.com/discussions/schiit-reference-sytem-review-freya-into-yggdrasil-into-vidar... 

Given your statement, at what decibel level do you consider the volume to be something "higher" than lower volume? The essence of the question is at what power level do tubes no longer "rule" over SS because of power concerns. Thank you.

Its not so much a decibel thing as it is a distortion thing.

Take a look at the distortion curves of a typical solid state amp. At a certain lower power level, the distortion is at its minimum and as you go to lower levels the distortion can be significantly higher! This is not a given with tube amps, even push-pull amps (our amps are push-pull but distortion linearly decreases to unmeasurable as power is decreased).

So that power level is about 5-7% of full power with most solid state amps. If you've ever heard that bit about the 'first watt' being the most important, that's because its all about distortion (or in this case, the lack of it). BTW, Nelson Pass has a set of solid state amps called the 'First Watt' amps and they are so-named because they diverge from the usual solid state amps in that they too are very low distortion at low power levels. Their designs are also quite minimalist (even simpler than and not unlike tube amps in that regard) although they don't make a lot of power.

If you want good resolution so you hear everything (including good bass) at lower levels, this is what you have to do: tubes or a low powered solid state amp like a First Watt.

Now to the latter portion of the question- even at high power levels, the presentation continues to be all about distortion (or the lack of it). The thing is, the ear weights certain forms of distortion over other forms. What I mean by this is most people understand that the ear hears sound pressure on a logarithmic curve. What is considerably less understood is that the ear also detects harmonics on something that looks like a log curve. It is far more sensitive to higher orders (in particular the odd orders) than it is to the lower orders like the 2nd or 3rd harmonic. For this reason, we tolerate large amounts of lower ordered harmonic easily, but don't tolerate higher ordered harmonics well at all.

Audiophiles have terms for trace amounts of higher ordered harmonics; 'bright' and 'harsh' are common examples. This continues to be the big difference between tubes and solid state with regards to distortion! Now think about that weighting issue I mentioned: essentially, solid state amps have much **greater** amounts of distortion if you weight the distortion according to how the ear/brain system responds to it (all forms of distortion are converted to a tonality of some sort BTW). So a 7th harmonic at 0.005% is a much bigger sin in terms of coloration than a 2nd harmonic at 1%. Its a bit of an inconvenient truth.

Our measurement and testing regime is a good 40-50 years behind our understanding of physiology at this point, which is why there is still a tubes/transistors debate going on in high end audio.

@ leemaze

I'm amazed at how much deep bass I can hear at low volume after installing Cerious Technology Graphene Extreme speaker cables.  Yeah, yeah, let the flaming begin, but I've tried other cables.  In my case, I found a big difference and nice increase in being able to hear super low bass with the sound not turned up high at all.  That said, for intelligibility of vocals and higher frequencies, you do have to turn it up enough to overcome any ambient noises.

@atmasphere

I’m very appreciative of your rather detailed and informative last post herein.

I know I read from you elsewhere on the forum (and quite a while ago now and paraphrasing) that all amps distort less as their power level is decreased, but must have missed the fact that this would only by to a certain point, after which distortion increases.

Also rather interesting that you should point out the relationship distortion has with harmonics and how you consider "weighting".

Honestly your write-up is analogous to Shakespeare. You just can’t read it once and claim to understand it :) I’ll copy/paste to a word file so I can more readily refer to it.

Thank you so much.

Also rather interesting that you should point out the relationship distortion has with harmonics and how you consider "weighting".

There is always more to it...

We all know about Fletcher-Munson. The Fletcher-Munson curves show where our ears are most sensitive, which is birdsong frequencies. This is because birds are the first indication of a predator in the vicinity and their calls activate other birds to spread the alarm. It does not matter if you are predator or prey, if you can't hear birdsong you're likely hungry or eaten.

The harmonics of a good number of instruments happen to fall into this region which is up to 7KHz. So the instruments that are making the most energy in music have harmonics that fall in the range to which our ears are most sensitive. This is likely not coincidence, but it presents a daunting challenge to engineers if the goal is to get audio systems to sound like real music and not an audio system! 

Traditional engineering tends to ignore this, although we've known the Fletcher-Munson curves for decades.

One example of this is the use of loop feedback in amp and preamplifier designs. Feedback is known to bifurcate the input signal and thus generate harmonics of its own while also suppressing distortion. For this reason feedback usually contributes to brightness in all amps in which it is used; this brightness is caused by distortion rather than frequency response error. Our ears use the higher ordered harmonics to sense sound pressure, so any addition to these harmonics (or their presence where none was before) is easily heard, despite not being all that easy to measure.

The audio industry is a long ways from acknowledging this fact so we can expect amps to have a tendency to brightness for some time to come. One of the few areas where there are deviations from this norm is in high end audio. Its a weird world...