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Old 17th June 2012, 05:15 AM   #1
routhun is offline routhun  United States
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Default 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?

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Old 17th June 2012, 05:21 AM   #2
routhun is offline routhun  United States
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Here is the sinewave output.
Attached Images
File Type: jpg IMG_20120616_200007.jpg (906.5 KB, 78 views)
File Type: jpg IMG_20120616_200015.jpg (947.0 KB, 68 views)
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Old 17th June 2012, 06:34 AM   #3
Mooly is offline Mooly  United Kingdom
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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.
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