Convert to cathode bias

To calculate this resistor, use Ohm's law:

R=-32V / 0.088A

(remember that there are 2 tubes, each drawing 44mA). R=364 ohms. The wattage of the resistor

(power) = 0.088A * 32V = 2.8W.

To be on the safe side, double this and use a 5W resistor. You can either work up a combination of resistors to get 364 ohms, or use the closest value you can find. Check it in the circuit to see that the tubes are biased within a safe range.

A bypass capacitor will have a noticeable effect on the sound. It can be calculated using

C=1 / (2 * pi * R *f)

where f is the frequency that you'd like to start the bypass. If f=20Hz (the lowest part of the hearing range), C = 22µf. You can play with the frequency you select to change the sound of the amp. This cap can be switched in and out by inserting a resistor between it and its ground connection, and adding a switch to short out the resistor. The resistor should be about ten times the size of the cathode resistor. When the switch is open and the resistor in in the circuit, the bypass cap is effectively eliminated. Switching this way eliminates popping.

The cathode resistor will generate a fair amount of heat, so keep it away from its bypass cap and other components.

If you are building from scratch, and can't measure the bias voltage and current of the tubes, resistor values can be found in tube data sheets, or you can use trial and error. Start in the range of about 500 ohms, get a bias current reading and adjust from there.