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previous: Joe Looking at the slo scheme, I have a... -- 1110461870 View Thread

Re: SLO 2.2M after 3rd stage?

3/11/2005 8:29 AM
MattRe: SLO 2.2M after 3rd stage?
I'm not sure I understand your question but it looks to me like the 330k resistor from the clean channel (R18 in my schematic) is the 'load' resistor when the opto is on. The resistance in the opto when on should be in the 1k ballpark. So when the opto is on, the load on the output of the previous stage is 2M2 in parallel with ~331k (the opto resistance plus 330k). The load on the input to the following stage is 220k plus the resultant load of the 330k in parallel with 2M2 (I left out the 1k opto resistance because it's negligible compared to 2M2).  
The amp will probably work without the 2M2 there at all, I'm not really sure of it's purpose. Maybe some funky things happen to the previous stage when it has a load of around 50M and it messes with the clean channel. The opto resistance when off should be in the 50M ballpark IIRC.

joe Yeah, I pretty much wanted to know ... -- 3/11/2005 4:02 PM