You're not bothering me.OK thanks for the clarification. The potentiometer was always in circuit.
I am still at a loss then to explain why you could test various resistor values from the non-inverting input to ground (or at least in parallel with the pot wiper to ground ?) and obtain a change in output offset whilst adjusting the volume control setting had no effect at all. The latter variation in potentiometer setting is in principle equivalent to placing the various resistors across the potentiometer. If that's not the case then you seem to have discovered an interesting phenomenon that appears to be at variance with expected circuit behavior.
Unless your circuit was actually as shown in the attachment with the potentiometer orientated the other way around ....
I shan't bother you any further but leave you with that conundrum to consider.
Good luck with your project!
No, I drew the circuit correctly. The volume control is oriented just like the one in the headphone amp above...not like you posted.
Just for clarification, when trying different resistor from the inputs to ground I left the volume control near its minimum(as for volume level) position. So this would be close to 10k ohms.
Initially, when I only had the 1K resistor in series with the pot, I did vary the volume control while measuring the offset as you or someone here suggested.
Varying the pot had no effect on the offset as it was 1.6 volts anywhere I set the pot.
Based on what I see and everyone's recommendation here, I see no way to use the AD828 for amplifying audio.
I think it could be made to work as a buffer, but not much else in the audio field.
I have taken it out of my circuit and reinstalled a FET input op-amp.
Now the offset is only a few millivolts...just where it should be.
Thanks again guys!