Hey Rick (or anyone who wants to chime in),
I just salvaged some 5886 submini pentode/triodes and I was wondering if you might have a circuit suggestion for them. They are high gain, low voltage, and the cathode is direct heated (I think that's the correct terminology).
Hey Alex, pretty similar to 5672 in many ways, here's a pinout comparison:
5672 pin 1 = 5886 pin 1
5672 pin 2 = 5886 pin 2
5672 pin 3 = 5886 pin 3
5672 pin 4 = 5886 pin 7
5672 pin 5 = 5886 pin 4, except that it would appear that this is also the filament -ve.
The heater appears to want 1.25 volts / 10ma, an LM317 would be a good option. But my calculations suggests a 1K 1
watt resistor would drop the voltage nicely. That current draw is measly! The plate voltage is really low at 22.5 volts.
So try it out in a Pentaboost type circuit, then cascade two for a Pentadriver. Look at Delirium if you want tremolo, but you may have to tweak the 43K/47K voltage divider. All the schematics are easily accessible by the link in my signature. Have fun, expect microphonics!
I'll take this opportunity to shamelessly plug the follow-on circuit from the 5840 Boost: "Promiscuous Girlfriend"
EDIT: Also have a look at tranceracer
's 6418 build: http://www.diystompboxes.com/smfforum/index.php?topic=76388.msg624839#msg624839