[Ericus Rex]

I'm no expert on nuttin' but I'm definitely no expert on solid state stuffs. I've got this stereo bass amp I've rebuilt and one side of it is giving me this strange active distortion on the lower half of the sine wave.  What could be the cause of this?  Thanks!

[AllanS]

Curious… I’m sure that I’m less of an expert but is it just the lower half that’s distorted?  The upper half doesn’t look clean either.  It looks to me like the upper is more compressed than the lower but still showing distinct responses.  How does/do the waveform(s) compare to the other side?  Is the distortion frequency dependent?

[FullRangeMan]

My 2 cents are, Iam not a tech guy but came to mind output Transistor mismatch.

[Ericus Rex]

Here’s the other side. Looks good to me. Most of the problem is with the bottom peaks jumping around. But the top peaks look a bit pointy to me as well.

[FullRangeMan]

The lower signal are the - negative part of the wave. This is a Class B or AB amp ?

[AVnerdguy]

Oscillation. Possibly caused by poor time constants in the output feedback loop. Look for wrong value or devalued capacitors/resistors. Could be as simple as poor solder joints also. Difficult to diagnose without seeing the circuit