lm4780 crossover distortion at higher output levels

routhun · 17th June 2012, 05:15 AM

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 · 17th June 2012, 05:21 AM

Here is the sinewave output.

Mooly · 17th June 2012, 06:34 AM

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.

17th June 2012, 05:15 AM	#1
routhun diyAudio Member Join Date: Mar 2005 Location: Sunnyvale	lm4780 crossover distortion at higher output levels 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

17th June 2012, 06:34 AM	#3
Mooly diyAudio Moderator Join Date: Sep 2007	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. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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