Amps with few tubes

[Rhodesplyr]

One of the amp chassis I've been given over the past year is a Spartan/Magnavox AMP-151BB, a small chassis with one 12AX7 and two P-P 6AQ5s. From the documentation I have on it, it was apparently meant to be used with a crystal phono pickup. The 12AX7 is wired as a single amplification stage/paraphase inverter.

If DIY'ers have done so, I'm wondering how they have converted amps like this for musical instrument use since one 12AX7 is not a lot to work with. I suppose it could be used as a stand-alone output stage with preamp tubes on another chassis...

[MWJB]

You could rewire the 6AQ5 as self split, push pull, using the 12AX7 as input stage & recovery stage after volume & tone controls? Add a bypass cap to the 6AQ5 cathode resistor & you get a SE option too.