Ideal Volume level

There is no magic "o clock". All volume circuits would have to be identical in all gear. Actually, everyone would have to have identical systems.

At what volume your speakers perform best is a more likely determinant.

Same for your amplifier's output.

it's more a dynamic range issue. While said tracking differences may be an issue, I have yet to hear any preamp suffer from this effect (ie enough channel imbalance to notice center fill shifting)..that would have to be one hideous potentiometer!!!!

when you rotate the vol knob from zero sound on up you are raising the smallest parts of the signal out of the noise floor. When you do this you are increasing the dynamic range; those subtle signals give rise to microdynamic expression... ( in preamps we are paying dearly for signal attenuation and very low noise floor, if you want neutrality...if you want coloration this-ish PLUS something else)... I firmly believe this is the essence of "sweet spot". It is system dependent as others have mentioned (amp, speaker sensitivity, overall system resolution)...
I notice that my sweet spot moves to the right for every pint consumed, YMMV. TGIF!

I cannot turn the volume knob on my previous Plinius preamp past 10 o'clock or I'll destroy my ears(or burn something). I have the volume knob on my current ARC LS-16 preamp at 2 o'clock when I blast the system, well for just a short period of time of course.

Just use an SPL meter and measure the sound levels you're getting. Recommended is at 75-80db if I'm not mistaken. Listening at over 100db for prolonged hours is not recommended.

You need to think of volume in reverse. If you bypassed the volume control you would get loud full blast unrestricted sound. A lot of people would assume no sound. When you have no sound coming out, the volume control is actually on full. All a volume control does is attenuates the output of the preamp.

Everything is system dependent. The person who wants to have crystal clear blasted rock and roll is not going to build the same system as the person who wants crystal clear jazz played softly as background music.

Ryder,

I assume you mean 75-80 dB SPL with C weighting and ballistics set to slow. I find that a nice setting if I'm really listening, but I prefer 10 dB lower when I'm at my computer or reading.

A look at A weighting, a scale that attempts to incorporate hearing sensitity, shows that we perceive more at each end of the frequency spectrum, especially lower frequencies, as level is raised, yielding a better balanced sound. Many older receivers and some preamps had a loudness switch that contoured the sound as level was lowered to compensate for hearing sensitivity, usually on the basis of the Fletcher-Munson curves.

db