Question about active filter noise

[sol]

So my first attempt at making an active filter has not gone so well. The filter is generating tons of noise. I'm looking for some advice.

So far filter has two stages: an input buffer and baffle step compensation. Goal is to grow to be a 24 db Linkwitz-Riley subwoofer XO with baffle step for the high out and additional EQ on the low out.

When I connect the circuit, I get terrible noise and distortion. Noise is even present when there is no input: my two stage filter is a white noise generator.

Strange thing is each stage works fine by itself. Running signal through either stage is fine.

I'm using NE5532 opamps, 1% resistors, and Panasonic poly caps. Input is an iPod, for now. All together on a solderless breadboard. +-12v supply.

I based the design ideas on John Pomann's active filter kit site, as well as info from Eliot Sound projects, and other info I found from threads around here.

This must be something very simple that I'm missing. Any ideas?

[clem_o]

It might be oscillating. Solderless breadboards won't really give you the signal layout / grouding / good connections that you want for a high-gain opamp application.

Have you checked your power supply as well? Are the power lines properly decoupled? Have you checked your grounding scheme?

Cheers

[phase_accurate]

Are the power lines properly decoupled?

I second that and I'd like to add that you'd have to pay special attention to 78xx and 79xx voltage regulator ICs if you use such.

Regards

Charles