Josh, I don't think you need to regulate at all. The class-A preamp stage will draw a fairly constant current, and the voltage is not especially critical. Just select a series resistor to drop the right amount of voltage and add an electrolytic filter cap after it for hum reduction, similar to StarTrek's suggestion.

The electrolytic should be rated at the full supply voltage, however, because there won't be any voltage drop until the preamp tube warms up and starts drawing current. Alternatively, lower the values of the voltage-drop and bleeder resistors to form a "stiffer" voltage divider that will limit the cap voltage during warm-up. Watch the power ratings on those resistors.

Note that the circuit referenced by StarTrek is not regulated... It just exhibits a lower output impedance than a simple voltage divider, and is variable.

Glass audio is a great hobby for the Winter months! [Linked Image]

[edit: Oops, wrong UBB code]

[This message has been edited by John Crighton (edited 10-05-2006).]