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Vintage threads from the first ten years

previous: R.G. Re: Cathode follower drive to output tubes -- 1/11/2000 4:04 AM

Re: Ah! I wish I wasn’t so ignorant!

1/12/2000 11:10 AM
lion	Re: Ah! I wish I wasn’t so ignorant! Well, I don’t know about this. It seems to be a little more complicated than I thought at first. Sorry for being so ignorant – but I’m not sure I can take-in what difficulties I’m facing here. Hopefully – it’s just because I (as usual!) don’t understand it: >In this application, you would do the cathode resistors either from the resistance you need to bias the output tubes right or if that didn't limit you, you'd size the source resistors to keep the MOSFET dissipation down, with all that B+ above it. If you sub them for tubes, you may have to take into account the difference between the few volts negative bias a tube needs and the few volts positive that a MOSFET needs. That might be critical if you're direct coupling the sources to the grids of your output tubes and need to get the bias DC voltage right.< I have to think it over. Thanks for all the help so far. Regards Lion

1/12/2000 11:10 AM

lion

Re: Ah! I wish I wasn’t so ignorant!

Well, I don’t know about this. It seems to be a little more complicated than I thought at first.

Sorry for being so ignorant – but I’m not sure I can take-in what difficulties I’m facing here. Hopefully – it’s just because I (as usual!) don’t understand it:

>In this application, you would do the cathode resistors either from the resistance you need to bias the output tubes right or if that didn't limit you, you'd size the source resistors to keep the MOSFET dissipation down, with all that B+ above it.

If you sub them for tubes, you may have to take into account the difference between the few volts negative bias a tube needs and the few volts positive that a MOSFET needs. That might be critical if you're direct coupling the sources to the grids of your output tubes and need to get the bias DC voltage right.<

I have to think it over. Thanks for all the help so far.

Regards
Lion