lm4780 crossover distortion at higher output levels

[routhun]

I just finished lm4780 amplifier based on PCB designed by Veteran. Although original PCB is for parallel operation, I am planning to use it for stereo configuration. I am encountering some weird distortion, at moderate to higher output levels. At lower levels (output is less than 500mv) there is no distortion, but it starts afterwards and stays like that. I am thinking it might be due to some oscillation, but not sure. Will post the pictures soon, anyone encountered such an issue?

Thanks,

 

[routhun]

Here is the sinewave output.

 

[Mooly]

That looks to be just lack of forward bias but is that even possible with that IC ? Oscillation would show as a thickening of the trace.

I wouldn't discount physical wiring layout/grounding scheme/arrangement too without seeing it all first hand. Is the IC running hot.