Volume controls and opamps Zin

[diy didi]

Hi all
I have a question with regards to an opamp feeding a volume control feeding an opamp again.
What is the min resistance I can use for R3 if the preceding 10k pot value is a given.
Is it in any way determined by the value of the 10k volume pot?
The attached circuit is in no way the actual circuit in use, but just a quick drawing I made to get my question across.
Sorry for the jpeg.
Thanks.

 

[Nigel Goodwin]

In theory it should be at least 5 times the volume of the pot.

However, if you use a linear pot for the volume you can 'make it' log by using a smaller value load resistor, I've done just that recently based on this article.

https://sound-au.com/pots.htm#chg-law

 

[crutschow]

The value of R3 also determines the value of C1 needed for the minimum frequency you want to control (typically 20Hz for audio).

 

[audioguru]

Why are the opamp circuits both inverting with such a low input resistance? A non-inverting opamp circuit can have a very high input resistance, then the volume control can also have a high resistance and a lower value coupling capacitor can be used.

 

[Nigel Goodwin]

Why are the opamp circuits both inverting with such a low input resistance?

You're not reading the posts again AG!.

The attached circuit is in no way the actual circuit in use