Charge pump capacitors on A4982's sing

[jetty840]

The charge pump 0.1uF capacitors on the CP1/CP2 pins on the A4982 sing emitting a high pitch sound which can be detected by and is irritating to younger users, approximately 12-16KHz.

The charge pump operates at 52KHz, with a superimposed waveform of approximately 6-8Khz at 8V peak to peak. This causes the piezo material in the Y5V capacitor to emit sound due to the piezo electric effect at the fundamental and resonate at the 1st harmonic. Frequency can vary slightly from driver to driver according to manufacturing tolerances in the A4982 charge pump circuitry.

A 14dB improvement can be achieved by replacing these 4 caps with a X7R Kemet P/N C0805C104K1RACTU.