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Safer SID

Project: Protection circuit for SID
Target : C64
Time   : 20 min
Cost   : ~1 US$
Use    : Protect the SID from overvoltage.


See figure below.


The SID cannot take more than 3Vpp or 1Veff, respectively. Therefore, if you use the SID audio input, the input voltage should be limited. The circuit below limits the input signal to about 1.4Vpp. This is done by two antiparallel silicon diodes which cut off the signal at +/- 0.7V. The resistor limits the current coming out of the audio source.



  1. Build the following circuit:

    [SID protection circuit] (Click here for ASCII version)

  2. ... and stuff it in a DIN plug for the AV jack.

Possible failures

Updated: September 30th, 1997
Created: February 3rd, 1997

Site copyright © 1997 by Marc-Jano Knopp
This document is part of MJK's Commodore 64 & LCD Page
Brought back to life by Peter Schepers, Dec 10, 2005 because I really liked this site!