Re: Impedance converter for electric guitar


"Andre Majorel" <cheney@xxxxxxxxxxxxxxx> wrote in message news:slrng38g2p.3oe.cheney@xxxxxxxxxxxxxxxxxxx
My search engine skills must suck. I've been looking without any
success for the schematics of a DI box. The goal is to plug an
electric guitar or bass into a line input. The specs would be :
- one high impedance input (couple megohms),
- one unbalanced line output,
- unity gain,
- +/-15 V supply prefered, 9 V supply OK.
- preferably only jelly bean components. In particular, no
transformers. :-)

Would a TL072 voltage follower with a 5 M resistor to ground on
the non-inverting input do ? Or is there more to it than that ?

Thanks for your help.

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Cette supposition rappelle assez celle de ce prédicateur qui, en
pleine chaire, faisait remarquer à ses fidèles la bonté de Dieu qui
avait placé les rivières auprès des villes." -- Alexandre Dumas

A simple voltage follower as you describe would certainly work, but I have to ask:- Why no transformers, why an unbalanced output, and why such a high input impedance?

If you're taking the cable any distance, especially in an environment where there are lights and lighting controllers, I would much prefer a balanced connection. If so, then transformers have a great deal going for them, mainly in providing full galvanic isolation between the instrument and the rest of the world. A couple of megohms input impedance also seems very high, is there a reason for it?

S.



--
http://audiopages.googlepages.com

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