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Re: Pentode preamp

11/10/2000 1:27 PM
Re: Pentode preamp
I like the old Gibson Les Paul amp preamp, I think it's a 5789? That's pretty cool sounding, also I have a pedal that's a Vox AC-4 preamp, but modified to use commonly available 7-pin valves. You can try about 100 different kinds of valves in there, no sweat.  
At present I'm using a 6AG5, but it can handle 6AU6, 6BE6, all kinds of tubes. It might be worth breadboarding something up and swapping tubes until it pleases you.  
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11/10/2000 6:33 PM

Thanks Pharaoh! Anyone else?
11/10/2000 9:05 PM
Chris B

Try a 6SJ7, like the 5C1 Champ. Never tried this, but I may in the future. According to the RCA tube manual, with 300V B+, an amplification factor of 259 times the input is possible.  
Chris B
11/11/2000 2:54 AM
The 5879 based "Low-noise microphone preamp" circuit out of the back of the old RCA receiving tube manuals is a great preamp stage, when your goal is super-clean, super-quiet voltage amplification, without a lot of frequency response shaping. I built one a long time ago to boost guitar signal levels up to "line level" for trying out various oddball tube gear garage-sale finds. The preamp was very, very sweet sounding, and another "plus" is taht it requires a minimum parts count to implement it.

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