I'm trying to build a guitar amplifier and I've run into some problems that I can't understand.
The input has an op amp to buffer and amplify the guitar signal which looks like this:
Open wires on the left are where the guitar is supposed to be connected (I'm measuring it with no input) and out will go to a tube, but I've taken it out for testing now.
My problem is that without any input I'm expecting (and the simulator agrees) the circuit to output almost exactly the voltage of the virtual ground (2.04V, from what I've measured), but I'm seeing 1.45V -- 0.6 V lower than expected. The values measured are DC; when measuring AC everything shows 0 exactly as I would expect. Also my amplifier has two identical channels and the second one shows almost identical voltages -- I think that it decreases the probabilty of the problems being caused by my soldering.
I've checked all the voltages around and tested continuity to see if there aren't any unexpected shorts, but I didn't find any other problems than this, but I've run out of ideas. Are there any obvious problems with my design? What else can I try to find the problem?