Noise problems with HP amp
Hello to everyone.
I've got some noise problems with a headphone amp and I'm not shure how to fix. The schematic is attached. The HP amp is driven directly by the output of another NE5532A (not shown in the schematic).
I have noise problems with some digital signals from the rest of the circuit which I can hear through the phones. The strange thing is, that the noise disappears when I touch the input pin by hand.
A 100k resistor or a 100nF-10µF capacitor connected from input pin to GNDA doesn't help. The signal GNDA is NOT connected to mains earth/chassis.
Can anyone give me a hint how to suppress that noise?
Thanx in advance!
Make sure you have bypass capacitors between the +15 rail and ground and between the -15 rail and ground. Try .1uf.
One of the chips may be oscillating.
You may want to insert a low value <100 ohm resistor on the output of the BUF534. Put it in series with the output before the R4 feedback resistor.
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