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A question about system and stage gain balance.

Posted by kyle (A) on October 14, 2016 at 08:20:56

Many people use active preamps that may have output voltages of over 10 volts. Why make DIY amps that have 1 volt input sensitivities if you use a pre with that much gain and available voltage?
Would it not make more sense to have a balanced gain structure that could utilize more of the preamp's output?
As an easy example and ignoring personal tube preferences; if you make a 300B amp with a 6SN7 driver loaded with a CCS, you could run the driver tube at 250 V P-K from a 350V supply, 10mA and -6V on the grid. The 6SN7 has a mu of 20, most of which is available if CCS loaded, so it could easily drive the 300B grid to 80 volts with ~4 volts from the preamp. The curves still look good at these op points and there's no stress on the tubes.

Is there a downside to this approach? Is there another reason that DIY amps seem to have 1 or 2 volt input sensitivities?
The discussions I've found in searches are vague or very specific to individual amp/pre combos.

PS, I'd like to say in advance that I don't care about opinions on transformer wire size, mentors from ancient history, transfer whatever or tube types. Just the gain balance question. insert happy face here

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