I designed a stereo audio amplifier using the TI LM4766 and I’m seeing noise riding on top of the sinewave. Please see attached pictures (no noise, noise, noise plus clipping). This is a single ended, stereo (2x20W), 42V rail amplifier. Please see attached screen shots of the oscilloscope. Thank you.
The load is six ohms The audio amplifier is in the bottom of the picture labeled Audio Amp. It has the heatsink and LED’s showing. The power supply is in the same picture and on the top shelf. Issue shows up at maybe ¼ full power. Below that it’s okay
The noise is present when powered with a bench top power supply (see pictures). However, when I removed the Csn capacitors on the output (C14 and C31) it would go away. Any guidance/applications notes on the Csn values for a single ended amplifier with AC coupled outputs?
