API 312 470uF output cap

[JW]

This has been discussed a couple times https://groupdiy.com/index.php?topic=40582.0 but I have a couple more questions. This cap being used in series from the amp output to the output transformer, with a 47 ohm resistor in parallel with the cap.

If I were to use a polarized electrolytic cap, would the negative side go toward the transformer?

And what is the advantage here of using a bi polar cap vs a polarized one?

 

[Bo Deadly]

This has been discussed a couple times https://groupdiy.com/index.php?topic=40582.0 but I have a couple more questions. This cap being used in series from the amp output to the output transformer, with a 47 ohm resistor in parallel with the cap.

If I were to use a polarized electrolytic cap, would the negative side go toward the transformer?

It doesn't matter because polarized caps do not have a problem with a volt or two reverse bias and the output offset voltage of the OA will likely be only a few mV. But if you have to choose, the output will be positive or negative depending on the input of the OA. IIRC if the input is NPN, then usually the offset will be positive and PNP negative in which case you could orient the cap accordingly. But I could be wrong about that. There might be something about the OA you're using that would affect pos / neg offset.

And what is the advantage here of using a bi polar cap vs a polarized one?

None that I know of.

 

[NadMk]

Use a tester to find if you have positive or negative DC at the output of the OpAmp, so you can find out the polarity.