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previous: Josh has anyone built or heard an amp wi... -- 7/31/2000 12:53 AM View Thread

Re: what do pentode preamps sound like?

8/5/2000 11:31 AM
RichRe: what do pentode preamps sound like?
There's a low noise microphone preamp schematic in the RCA receiving tube manuals. I built one to use as a guitar preamp (for clean tone). There is also a tone-control stage in the schematics section, which I placed in the circuit after the mic preamp.  
The mic preamp used a 5879 pentode, and I think the tone stage used a 6EU7, although a 12AX7 would be fine if you changed the pinouts.  
The preamp I built was very clean, very quiet, and never became microphonic. At the time I played a Gibson 335, and the homemade preamp was connected to the input of a Macintosh MC30 power amp (two 6L6's, 30 watts RMS) used with a JBL D130 in an open back cabinet. For Jazz and other clean playing, that rig was pretty hard to beat, with a "Magnatone" type of sound.