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opto channel switching

4/10/2000 6:11 PM
opto channel switching
Can anyone give me a quick rundown about how to use an optoisolator for channel switching? I've got a salvaged SF Bandamaster chassis that I want to rebuild as a two channel switcher. I'm going to use the trem tube as a another gain stage / cathode follower and thought that I could use the opto for channel switching. I've got a 6vdc mechanical relay, but have a sense that switching with the opto would pose fewer problems for switching noise. Is this true?  
Opto basics: What kind of voltage does the bulb require? Is this just 6.3v? Does the resistance go up and look like an open circuit or go down and look like a short when power is applied?  
My thought was to run both channels in parallel allowing the high gain channel to swamp out the clean channel when in the high gain setteing, and then shunt the lead channel to ground for clean.  
Any good articles or schems to reccommend?  
4/10/2000 10:33 PM

Basiclly this is what the SLO does (swamping the clean channel when in lead mode), however you'd most likely want to use (2) opto's. One to ground the grid on the gain stage in the lead channel right before the two channels connect. The second going to ground right before the actuall connection of the two channels. Check out the scheme for the Soldano SLO on Steve A's site.
4/11/2000 8:28 PM

Thanks Ryan. I got the schem. This is very much what I had been thinking. Do you know if the fender trem roach will work in this application? I've seen people selling the trem roach and channel switching LDRs as two different things (diffr'nt prices that is)and wondered what the difference was.  
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