Electronic – NE5532 strange oscillations

amplifieroperational-amplifieroscillation

I am designing a small audio amp and am experiencing some weird oscillations in the first OPamp (NE5532), wich is setup as a noninverting amp. The amp is supplied with +-20V and has 100nf bypass capacitors directly at the supply-pins.

schematic

simulate this circuit – Schematic created using CircuitLab

Only the inverting input pins are oscillating at 250kHz with an amplitude of 2V.

The supply is linear regulated (LM317,LM337) and has no measureable noise/ripple.

What could be the reason?

Thanks in advance

EDIT:
I noticed, that the oscillation is quite intermittent. Then the smallest amount of signal on any pin will retrigger it.

Best Answer

Try it with 10pF-100pF across R1, to reduce the phase shift on the inverting input. Even with 100pF you'll still have fairly flat gain across the audio bandwidth.

And I'd strongly recommend dropping the supply voltage to +/- 15v, for thermal and lifetime reasons if nothing else. +/- 22v is a survival rating, not a recommended rating.

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