H Richidoo,
Oh boy, you brought alot of questions.
"I believe that a low distortion system is most enjoyable, even over romantic sweetness. 'Real' is amazing and awesome, which is where my head wants to be.
That's why I was intrigued by this thread about your 11A preamp with no sonic signature which is completely transparent except for gain. The reason I am so curious is because like many of us, my system already has too much voltage gain. My weakest source (in voltage output), SB3, has an external linear power supply making 2A @5V which enhances bass and body tremendously, as expected changing from the stock POS, oops... I mean PS...
I run SB at 3/4 throttle max. My tuna runs at 1/5 throttle, as does my phono pre, all with their own volume pots coloring things up. These are all low output impedance (~220-600Z) driving my Manley Snapper monoblocks with 450kohms input impedence directly through Grover's interconnects with very low resistance and capacitance. They all sound awesome except for some digital crap from the SB with the digital VC, and I'm not sure that's not imagination anyway. So, I can't understand how these sources would need any additional voltage or current gain to drive these amps to their potential."
It seems everyone is adding gain, but then adding circuitry adds profits. I wish the different manufacturer's of different parts of the system would just design what is required and not add the extra's.
"And Yet ! when Stereofool or Carlman bring over their Mac or AR preamps, the sound seems to be fuller. It is even a little fuller sounding than the built in 6922>6SN7 preamp in my integrated amp. Is this fullness and body that their preamps add actually a coloration deliberately added as a voicing preference of the designer, or is the fullness a function of the preamp actually enabling better signal transfer from source to amp resulting in a sound that is actually truer to the recording?"
Probably neither. They probably do just a "voicing" session with their reference systems. I don't read where they do any exotic testing of any kind. Correct me if I am wrong though.
"Passive resistive, optical and magnetic volume controls are growing in popularity because they are cheaper than high quality active stages (no expensive PS to build),"
Actually, the optical, magnetic actually need a ps to work. Power has to be supplied to the lighting circuitry in the optical and magnetics to work.
"and they provide the functionality of a controller with volume control and switching. But are passive users missing something? Concensus among cognoscenti seems to be yes. But I would like to know what a truly transparent preamp is doing to the source signal (while also attenuating it to a lower level) that makes it a "better" signal for the amplifier."
It really does nothing to the source signal, just passes it with some gain. The differences one hears is the other preamps coloring the music.
"I guess a resistive attenuator will restrict current as it lowers voltage so providing a current gain source is valuable after the VC. But with magnetics you don't have that problem, and yet Promitheus is still selling a tube buffer stage for his TVC and apparently it makes a big difference. Is it artistic voicing, or basic physics? I'm sure it sounds great whatever the reason...
"
Not a current gain as you mention earlier in the sentence. The buffer stage is probably "colored" sounding if it changes the sound. The high input Z of the amp should not load a cd player at all, unless it goes quite low.
"Even the better phono preamps where 60dB of voltage gain is really needed are often separate components now, offering their own 2V+ low impedance signal."
And how good is their buffer stage? I would check their line preamps to get an idea.
"On the other hand, the Altmann BYOB amp I have been reading about has <10k inputZ and lower gain than normal due to battery PS, so there is still a case for voltage gain in a preamp."
I wish the input Z was higher, but their design may preclude such. For instance if they use a bipolar transistor, the input Z is quite low. If they lower the current through the transistor to raise the input Z, the transistor sounds different and that is what they might want to stay away from.
"Since 11A is reviewed as one of the very best preamps available for sound quality, I'm sure you will have some insight into my confusion."
In general, I find audio becoming a mixed bag with alot of manufacturer's competing for every part of the system. If the dac has alot of gain, why; and why so much gain in the amplifier? Now phono stages are coming up with their own schemes with more gain so as to crowd the line preamp market.
Only problem is that in such configurations, how does one check these extra stages vs a straight wire? Very difficult. I wonder if the phono makers actually check out the "preamp" stage(s) first before designing the phono stage itself? I doubt it.
