There are two 12k resistors to +v....dogears said:A friend sent me this snippet, I believe its from an old Midas desk. Simple enough op amp arrangement, but I'm not sure I understand the purpose of the 12k resistors to +V?
Is it creating a higher output bias voltage since the desk is single supply?
To create the voltage divider that biases the capacitor with a DC voltage.dogears said:Makes sense... but why the 1k back across C4?
This is pretty basic stuff.... but I'll play along for now. Perhaps find a book on basic electronics to read.dogears said:Not trying to be dense, but in that case why not just omit the first capacitor altogether?
Yeah, I just didn't get it. If I were recap I'd at least start by removing the biasing and leaving the tantalum. Or measuring the offset voltage to begin with.squarewave said:Two electrolytics back-to-back with / without a bias voltage applied is supposed to reduce distortion with cheap electrolytic capacitors. Yes, you could just replace both with one tant. I think that's why it shows the tant option there. But today even the cheap electrolytics do not need this sort of jury-rigging. So this circuit is not really worth exploring for it's design. If you're trying to decide how to recap and with what, that is a different discussion.
Also this does not look like it's single-supply. Otherwise C3 would be reverse biased and the input transformer would require a cap.
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