OT HIFI amp mod

[WeAreAs1 at aol.com]

In a message dated 6/5/00 6:37:15 AM, you wrote:

<<One of my friends is playing guitar through an old hifi amplifier. He uses

an aux input, I think. The build in radio sounds alot louder (ofcourse).

Someone told him that it would sound better if he 'bypassed' the amp (that's

what he told me, however, it probably sounds best if he just puts on the

radio... :) The amplifier is stereo, he only uses one channel at the

moment...

Now my question; what did the bypassing guy mean, and how do I do it? Any

other mods, considerations on this?>>

Hello Roel,

Congratulations on the completion of your schooling!  (and your very 
ambitious MIDI-CV project)

I think your friend needs to put a pre-amplifier between the guitar and the 
hi-fi amp.  The built-in radio has an output level that is probably much 
higher in amplitude than the output level of a guitar pickup.  Most hi-fi 
amps expect to see an input level that is somewhere near "consumer" line 
level (about 1 volt peak-to-peak), but a guitar pickup usually only puts out 
about 100mv or so.  A simple one-opamp preamp with a gain factor of about ten 
would take care of the problem.  The MXR Micro Amp circuit is very simple and 
would probably be ideal for this purpose (you can find it at one of the 
popular online FX sites, such as www.firebottle.net/stompbox).  However, 
you're probably right about it sounding best if he just puts on the radio, 
instead...

Michael Bacich

P.S. - If your friend does use a preamp to boost the guitar signal, tell him 
to be careful not to turn up too loud.  It's easy to blow up a hi-fi amp (or 
hifi speakers) with live music signals, which have much wider dynamic range 
than records or CD's.  Hi-fi amps and speakers are not designed to withstand 
such drastic dynamics.