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Originally Posted by Jim Williams Remove the 100 ohm resistors to improve crosstalk. |
Crosstalk of what exactly?
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Install a 100 uh inductor to trap rf.
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Unnecessary, it's not a 12ft long console, it's an 8 input mixer and IME the choke will cause all sorts of ringing problems.
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Replace the 10 pf feedback caps with 50 to 100 pf, stability will improve as the noise gain of the sum amp rises with the number of inputs summed. This also degrades the phase margin and can affect stability.
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It's designed to be only 8 inputs, not 48. I would not make this any bigger than 22pF unless you want to turn it into a slug - and it will depend on the opamp used too. The values shown will provide excellent square wave response with the OP275.
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If you use a low bias, low offset opamp like a Linear Tech LT1358, you can remove the coupling caps.
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As I mentioned above, the caps are there as a saftey measure to protect the opamp/transformer from DC entering the inputs.
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Put the transformer in a box so you can choose whether you want the flavor or not.
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Could be made switchable IN/OUT if desired.
Tim