I was wondering, I see so many of the F1/F3 or the A1/A3 tubes on ebay cheap and a lot are NOS. What is the difference. I know they are lower gain. Maybe grid driven? Somewhere I saw or read that the grid had to be isolated from ground? Just wondering if anyone had insight on this or could point me in the right direction to read up on this. Any help would be great.
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3cx....A3 or A1 tubes
- Thread starter Crusher
- Start date
Those tubes are low mu or low gain as you know and are typically used as modulators and oscillators that are grid driven. The A1 tubes are the lowest gain while the A3 tubes are medium. The tubes are cheap because they do not make good linear amplifier triodes.
Since you have to grid drive them to get any decent amplification factor, you also have to neutralize them if you're using them at RF frequencies. You'll also have to design a high impedance input circuit to drive the grid.
Now you have built nearly everything you need to make a super high gain tetrode amp other than the screen power supply, only to have a run of the mill triode. I'd buy the high mu triode of go the extra step of making the tetrode.
Since you have to grid drive them to get any decent amplification factor, you also have to neutralize them if you're using them at RF frequencies. You'll also have to design a high impedance input circuit to drive the grid.
Now you have built nearly everything you need to make a super high gain tetrode amp other than the screen power supply, only to have a run of the mill triode. I'd buy the high mu triode of go the extra step of making the tetrode.
Ok. Thank you Shockwave. You pretty much answered all I needed to know. I knew they were lower gain, just didn't know what was all involved. Your right. For all the extra work, stick with a #7 or just do a tetrode. More gain for the buck. Thanks again.
M
Mr Fix it
Guest
Crusher if your lookin for a tube I know a guy who has 5 econco 3cx3000f7 tubes for sale. Can give you his contact info if you want. I think he wants 50 or so for each tube. These tubes dont require a socket.
They look clean but are un tested. I was going to buy them but I have enough tubes dont need any more.
They are broadcast pulls
They look clean but are un tested. I was going to buy them but I have enough tubes dont need any more.
They are broadcast pulls
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