Working on a Hammond conversion, got a question.
I gutted the preamplifier of the first AO-35 chassis, taking out or rewiring mostly everything before the 2.2 meg resistor in front of the phase inverter. Now the preamp has 68k on the single input and and a 1meg grid resistor on the first triode, 1.5k at each preamp cathode. The volume and tone are between the two gain stages. I used this volume/tone
It's switchable between unbypassed preamp cathodes (good clean until 4/5 up the knob) and 1uf bypass caps, giving a good crunch as the volume increases (25uf didn't seem to give me that much more gain or more mids). It's quiet as a mouse at idle without the bypass caps and there's just a little hiss with them. I plan on adding two .001 caps in parallel with the plate resistors to roll off some treble, as the amp is on the bright end. Otherwise, it sounds pretty good.
SO -- question: Given the tiny chassis and fixed number of available triode gain stages, is there a better/less crude way of having switchable "gain" than switching those cathode caps in and out?