Lower cost LDR alternative

Question:

Jeff – It looks like they work in pairs, alternately passing and shunting the audio.  You could probably do the same thing with a simple DPDT relay, if you can stand a hard switch.  The advantage of the LDR is the "soft" on/off action. Anyone remember the predecessor to the LDR w/LED ? The Sigma Datacell, up to 4 switches in a package, with an incadescent lightbulb as the light source. …. tom – Hide quoted text — Show quoted text – > I’m lookinf for a lower cost alternative to using LDR’s (optoisolators) for > channel switching in my guitar amp project.  The schematic calls for 4 of > them and they will total about $30, just for switching! > Enclosed is a small part of the schematic showing how the footswitch turns > these on/off. > Any ideas? > — > Jeff Stapleton >                  Name: footsw.gif >    footsw.gif    Type: Paint Shop Pro Image (application/x-unknown-content-type-PaintShopPro) >              Encoding: x-uuencode

Response:

I’ve used cheapo radio shack DPDT relays, works fine. > I’m lookinf for a lower cost alternative to using LDR’s (optoisolators) for > channel switching in my guitar amp project.  The schematic calls for 4 of > them and they will total about $30, just for switching!

– Chris Thomas

Response:

> I’m lookinf for a lower cost alternative to using LDR’s (optoisolators) for > channel switching in my guitar amp project.  The schematic calls for 4 of > them and they will total about $30, just for switching!

Jfets are a tenth the cost of LDRs and offer the same isolation ratios. We will be updating our Kit page to include an Electronic Shunt relay kit, which has a four transistor control circuit that controls any number of jfets on either control line– six are provided– wired as shunt switches. The kit will be $25 US and can be built on a circuit card. For many more switching circuits and the most complete discussion of switching in guitar amps, check out "The Ultimate Tone", with more circuits in TUT2. For more info, see our site: <http://www.londonpower.com> Have fun Kevin O’Connor

Response:

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