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Volume controls and opamps Zin

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diy didi

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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.
422522DB-5730-4C87-9AC6-63EB87EE24C5.jpeg
 
The value of R3 also determines the value of C1 needed for the minimum frequency you want to control (typically 20Hz for audio).
 
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.
 
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