Tubes and power supply

[R.G. Keen]

>So I thought - I'll make a single pre-amp and a power supply which could
>vary the voltage from, say, 150V to 600V. But, all the IC's I know of
>are for voltages of up to 30V, and there are few transistors that can
>endure such a high voltage. And I'm not into regulating it directly with
>a pot. And I'm not that good with electronics (not to fool with 600V
>anyway).
>
>Does anyone have an idea how to make the above-mentioned power supply or
>could someone design it for me (I'd be eternally grateful - ok, most of
>my time using it, actually)?

Given a high enough DC bulk supply, there is a circuit for a high voltage 
regulator in the National Linear data book, using the LM317 to regulate 
hundreds of volts. The trick is that the regulator IC regulates current to 
keep a given voltage, and the high voltage is kept from blowing the 
chip by a series power mosfet which is biased 12V higher than the output 
voltage by a zener. This sounds simplistic, but it works well, I've used
it.

The power dissipation is essentially all in the power mosfet, which stands
both the series current and the difference between the regulated voltage and
the bulk DC supply.