[Dave_M]

Does putting a volume pot right before an inverting amp cause any problems? Looks like the series impedance of the pot will add to the value of R9 and will affect the gain. Even worse, it looks like the gain will change depending on the position of the pot.

The next stage (buffer) will invert the signal. I want to make the 1st gain stage inverting (like shown above) to keep the whole amp non inverting.

 

[flecom]

should be ok... if you want to look at non-inverting buffers there are a lot of designs on the gainclone pages

for some reason tho whenever i put that circuit into pspice it has almost no output signal... you might want to get rid of that 1 meg resistor i think

 

[Dave_M]

Quote:

Originally Posted by flecom /img/forum/go_quote.gif for some reason tho whenever i put that circuit into pspice it has almost no output signal... you might want to get rid of that 1 meg resistor i think

hmm that is not a good sign. I thought the 1M resistor is needed for it to work properly. But usually the value is lower, like 100k - 220k.

 

[Dave_M]

Maybe if R9 was made at least x10 the value of the output impedance of the pot it would work better. 120k should do it. I originally picked low value resistors for the feedback network to reduce noise. So, R9 should be 120k, R7 should be 680k to give it some gain. These values seem a little high. Could this make an audible differance?

Still not sure if having R9 = 1k would be a problem. I havn't seen any practical circuits with an inverting opamp at the input to an amp. Anyone?