Design notes

(In no particular order, here are some of the things I've noticed in building and playing with this. Most are wild speculation, and subject to change.)

• • The load that a tube drives (often the volume control) affects the tone. For volume controls, 1Meg pots have more treble than 250K pots. As a general rule, I seem to prefer 500K or 1 Meg volume pots, although there may be times when rolling off some of the upper end is desirable.

  • The larger the value of the cathode resistor, the quieter the volume (without a cathode bypass capacitor). Adding the cathode bypass cap will seem to have more effect on higher value cathode resistors because it makes a larger volume increase. It appears that smaller value cathode resistors may not benefit as much from cathode bypass caps.

  • Originally I hooked the 3rd tube and cathode follower plates to the first filter capacitor. This had a lot of hum. Moving it to the present arrangement helped a lot, but a full-wave bridge rectifier solves the problem.

  • In looking at schematics, the middle stage is often set up to pass 50-60% of its signal to the next stage. I think this stage sounds better with larger value cathode resistors, and no bypass. It doesn't seem like you really want much more gain here, just a bit. The lower value cathode resistors and the addition of a bypass cap seem to make the distortion buzzy.