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Vintage threads from the first ten years

Buffer Amp

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7/13/2000 11:00 PM
Bob	Buffer Amp Does anyone know of a schematic for a op-amp based buffer amp that I can build into a steel guitar that works off a 9 volt battery? It would be preferable if it were not a bi-polar supply but I want it sound good, too. What's a good choice for the op-amp? Thanks in Adv., Bob

7/13/2000 11:13 PM
Frank Clarke	http://www.harmony-central.com/Guitar/Faqs/faq/faq.buildPreamp.txt Low current or low noise?

7/14/2000 6:26 AM
Frank Clarke	Low noise opamps: http://www.muzique.com/schem/tips.htm

7/14/2000 1:16 PM
Liam	MXR microamp. Great as a buffer for most acoustic instruments. Quite a small 9V circuit, and I think it's on Aron's stomp box page. Liam

7/14/2000 1:44 PM
Mark Hammer	Steel guitars are reknowned for there signal level (hot) and potential dynamic range (Big). You might want to stick it out with a 2-battery job just to give yourself the headroom capability over the long haul. Buffers without gain don't necessarily eat up a ton of battery juice, but them big 9-string 13th chords can sound pretty shitty when your buffer crackles. IMHO

7/14/2000 4:12 PM

Why not use one transistor? Try the buffer section of the 3tran fuzz at arons site.

input to.1uf film to base of MPSA18(low noise)
470k from +9v to base
1meg from base to ground
collector to +9v
emitter to 10k to ground
.1uf film from emitter to output 100k pulldown from out of cap to ground.

Gain of about one in z ~= 1meg||470k this should be ok

FWIW simple transistor circuits are good at this type application.

current draw should be under 1ma

make sure to use a good electro as a power supply bypass 100uf is a good value.

7/14/2000 8:27 PM
Bob	Gentlemen, Thank you for you prompt replys, excellent infomation, and insightful suggestions. Much appreciated! Bob

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