Here's a sketch for a 1.25mA ccs suitable for your preamp. If you want to drop it to 1mA, change R1 to 1K. The reference string is set to pass 5mA through the LED voltage reference, which lowers its noise and impedance. You might want to bypass the LED with a cap- 470uF at 16V will be more than adequate.
The reference string can feed more than one ccs- if you're doing two, for example, all you need is a second pair of transistors and another R1. R2 should have a 2W rating; higher is better and wirewound will work fine. R2's value is not critical- a 47K will be just fine, as will a 51K.
Depending on your power supply, you might have to diddle the value of any series resistors to account for the extra 5mA of current burned up in the reference string. On the bright side, the LED gives a nice visual confirmation that the power supply is working. And if your supply drops under the additional 5mA, that will still be OK as long as the supply is 15 volts or more higher than the tube's plate voltage.
The transistor closest to the B+ rail does not need a high voltage rating- get a small signal PNP with a high hfe and ft. It's not critical.
(flo: bijvoorbeeld BC559)
The transistor connected to the 12AX7 plate needs to have at least a 300V rating. If its power dissipation is about 1W or higher, it will be fine without a heatsink. As before, the particular type is not critical- use what's easy to find.
(flo: bijvoorbeeld MJE350.
http://www2.conrad.nl/goto.php?artikel=156086 0,70euro)
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