fdegrove said:
Yep. I was thinking UP and typed DRD. Too busy shoving Thai food in my gob at the time.
http://www.welbornelabs.com/ultra.htm
I was thinking +24V, -12V supplies, LTP with a CCS in the tail and some nice 4:1 OPT's I have laying around. Just a thought experiment as I haven't got a use for it in my system.
Hello all-
Thanks PRR for the info in that post-- made testing a lot simpler.
The only issue I can think of is the fact that you have the tube running on +12V... When I then adjust values for the 6GM8 to run on 12V, will I need to change biasing or anything else? Thanks
EDIT: Instead of using resistor load on plate, would it be better to use a CRD so not as much voltage is lost on input? After all, the 12DL8 will mostly be a current buffer to the voltage gain from the 6GM8, and with my 300-ohm load, I may need a little bit of voltage.
Thanks PRR for the info in that post-- made testing a lot simpler.
The only issue I can think of is the fact that you have the tube running on +12V... When I then adjust values for the 6GM8 to run on 12V, will I need to change biasing or anything else? Thanks
EDIT: Instead of using resistor load on plate, would it be better to use a CRD so not as much voltage is lost on input? After all, the 12DL8 will mostly be a current buffer to the voltage gain from the 6GM8, and with my 300-ohm load, I may need a little bit of voltage.
> the 12DL8 will mostly be a current buffer to the voltage gain from the 6GM8, and with my 300-ohm load
Because of its wacky virtual cathode, the 12DL8 is not good as a cathode follower. Because of the enormous shift of bias current that happens before you get maximum output, it really is not going to like resistor or CCS loading. You'll just be disappointed.
It was designed to slot into a specific need, and is barely able to do that job. At its best is a comparative pig for power and a gross distorter.
Choke or transformer couple the 300 ohm load from the plate of the 12DL8. 800Ω plate load is good, but 300 to 2K will work. G1 tied to +12V, 10Ω cathode resistor, 100K signal grid resistor. I bet you get all the level and gain you need without any driver tube.
It may give usable output with +12 V to +16V(max) on G1, 24V or 30V B+, 500 ohm plate resistor.
Because of its wacky virtual cathode, the 12DL8 is not good as a cathode follower. Because of the enormous shift of bias current that happens before you get maximum output, it really is not going to like resistor or CCS loading. You'll just be disappointed.
It was designed to slot into a specific need, and is barely able to do that job. At its best is a comparative pig for power and a gross distorter.
Choke or transformer couple the 300 ohm load from the plate of the 12DL8. 800Ω plate load is good, but 300 to 2K will work. G1 tied to +12V, 10Ω cathode resistor, 100K signal grid resistor. I bet you get all the level and gain you need without any driver tube.
It may give usable output with +12 V to +16V(max) on G1, 24V or 30V B+, 500 ohm plate resistor.
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