Drain resistor for virtual earth

Just a quick question. In an inverting opamp stage, if using a cap (C1) to block DC from going back to the previous stage, is a drain resistor (R2) required, as one end of the cap is already connected to a virtual earth?

And the value of R2 (if needed) doesn't affect the gain as far as I'm aware?

Thanks

R2 is absolutely NOT needed. The feedback resistor provides a DC path for that end of the cap... If anything you might add a drain resistor to the other side of the cap to prevent switch clicks (if it is switched), since if left floating the cap will discharge to 0V across it and be sitting at the input offset voltage of the opamp. 

R2 will affect the noise gain of that stage, not the audio path gain.

JR

Nice one Just for a bit of clarity on your reply though, do you mean a switch in the feedback path for gain, or a switch feeding the input of this stage? (or both). It will be fed from a pot, which would act as the pre-cap drain resistor you suggest I guess.

Thanks

When you said virtual earth, I ASSumed a summer, where multiple stems might be switched in.

If the other end of the cap is connected to a pot, that will provide it's DC path.

For simple post pot gain stages I generally use both opamp inputs to differential between the pot ground and wherever I am sending the output signal to.

JR

Well yes it is summing, but only 2 channels. I wanted to have the following setup, but it looks like that would give scratchy pots (the 5k resistors). Is there anyway to solve this without buffering?

Thanks

Those pots will only be scratchy if there is DC being sent to them.

JR

OK thanks. I've just realised that what I was saying was totally wrong, if the pots were scratching then the cap would be completely pointless. Confused myself by thinking about it too much and forgot the fact that the main function of the cap is to stop the DC in the first place. Can you suggest any resources for reading up more on when and where a drain resistor is needed?

Thanks for your help.