Looking for a cheap tube to try for the front tube in a vari-mu compressor for a guitar amp, not a studio. I've already done a bunch of research:
Vintage tube compressors use the $$$ 6386 tube. I think a triode strapped 6BA6 is what is generally considered the best sub for that; it's even sold on the Manley Labs site. Yet on Fred Nachbaur's site he slammed the 6BA6 as often microphonic, and said the 6BJ6 is better. He used the 6JB6 in the Li'l 4x4 amp, and a 6K7 in the Dogzilla amp. There is also PRR's DIY vari-mu compressor which uses the 12AU7, but this design supposedly runs out of steam and can't deal with higher compression rates.
In any case, I'm looking for either a specific recommendation on a tube for this app, or at least a recommendation for a (very) remote cutoff pentode to try.
Vintage tube compressors use the $$$ 6386 tube. I think a triode strapped 6BA6 is what is generally considered the best sub for that; it's even sold on the Manley Labs site. Yet on Fred Nachbaur's site he slammed the 6BA6 as often microphonic, and said the 6BJ6 is better. He used the 6JB6 in the Li'l 4x4 amp, and a 6K7 in the Dogzilla amp. There is also PRR's DIY vari-mu compressor which uses the 12AU7, but this design supposedly runs out of steam and can't deal with higher compression rates.
In any case, I'm looking for either a specific recommendation on a tube for this app, or at least a recommendation for a (very) remote cutoff pentode to try.
smoking-amp said:
Ah! I assume you mean using the 6BN6 as a "roll your own cutoff"? Sounds a bit challenging, but possibly VERY rewarding. The references to "accelerator", "limiter", and "quadrature" are somewhat intimidating. To dumb it down a bit, is there something wrong with a starting point of strapping g2 to the plate, and biasing g3 positive with a zener between it and the plate?
EDIT: thinking about it some more, couldn't you bias g3 to the point where it becomes a vari-mu expander?
"Ah! I assume you mean using the 6BN6 as a "roll your own cutoff"?"
6BN6 looks complicated. But if you can figure it out....
I was thinking more along the dual control grid tubes. (You just put a control voltage proportional to signal envelope on g3 for compressor use. Or could just try direct biased up signal on g3 [and still g1] for some really potent distortion effects.)
Or, the many other remote cutoff tubes. George (Tubelab) mentioned the 6SK7 for instance, but there seem to be a bunch of others. 6SS7 for example. You need to rummage thru the GE Essential Characteristics book for them all.
Don
6BN6 looks complicated. But if you can figure it out....
I was thinking more along the dual control grid tubes. (You just put a control voltage proportional to signal envelope on g3 for compressor use. Or could just try direct biased up signal on g3 [and still g1] for some really potent distortion effects.)
Or, the many other remote cutoff tubes. George (Tubelab) mentioned the 6SK7 for instance, but there seem to be a bunch of others. 6SS7 for example. You need to rummage thru the GE Essential Characteristics book for them all.
Don
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