I'm trying to build a very simple headphone amplifier for my bass guitar. The bass has a built-in amplifier, meaning that unity-gain is sufficient for my amplifier, I essentially only need a voltage buffer.
To this end, I've used an LM358 (because that's what I had laying around) and a BC547 / BC557 push-pull output stage. Supply voltage is 9V which is overkill, since my signal is no more than 2 Vpp.
The problem is, that the output signal that I'm hearing is quite distorted. I can hear the clean signal but there are some undesired high-frequency components as well. Using an oscilloscope I was able to verify that the distortion is not due to clipping. However, I don't have a function generator, so I can't test if the culprit is cross-over distortion (shouldn't be though, since I've added biasing) or if there's some parasitic oscillation going on.
Anybody see a problem with the circuit right away?
Edit: I've been able to get a hold of a function generator. Here's a new scope screen capture (10kHz sinusoidal input) which seems to show some funny business around the zero-crossing. Blue = input, purple = output