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previous: John BRUCE, 5K? How about a 50K?... -- 2/29/2000 5:09 AM

Re: Varible 12ax7 cathode resistor in preamp?

2/29/2000 7:51 AM
Bruce	Re: Varible 12ax7 cathode resistor in preamp? Well once you get up that high in the cathode resistance you just about can shut the tube off. It will have a gain approaching 1-2 (or + unity) when the cathode is only half the plate load. I've used 56K cathode resistors on cathode follower tone stack drivers just for that reason. I think you'll be pretty suprised how little gain there would be even with a 25K pot. No harm in experimenting using 50K trimmer, but buy a 10K to try out too. Bruce

2/29/2000 7:51 AM

Bruce

Re: Varible 12ax7 cathode resistor in preamp?

Well once you get up that high in the cathode resistance you just about can shut the tube off.
It will have a gain approaching 1-2 (or + unity) when the cathode is only half the plate load.
I've used 56K cathode resistors on cathode follower tone stack drivers just for that reason.
I think you'll be pretty suprised how little gain there would be even with a 25K pot.
No harm in experimenting using 50K trimmer, but buy a 10K to try out too.
Bruce

Replies:

Richie I think sound city amps have a pot<... -- 2/29/2000 8:32 AM