Help troubleshooting noise please

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sonolink

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Joined
Feb 15, 2010
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London-Madrid
I built this ab763 preamp into a stompbox with an added DI output. When using the DI out there's a lot of noise (like wind blowing). I measured the opamp and I get 4.5v pretty much on all pins except pin 4 (0v) and pin 8 (9v). I tried replacing the Opamp but no go.
Would that be a busted cap that is not filtering DC?
Any help would be greatly appreciated.
Thanks

Sorry, now the correct schem is attached...
 

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Do you have an oscilloscope to see what the dc booster is doing for B+? Switcher supplies can make interesting noises.


I do have an oscilloscope. Do you want me to check B+ with it? Just asking, but if the noise was coming from the B+ supply wouldn't it be present at both outputs? Those voltages at the opamp pins are they normal? If not, how would those 4.5vdc end up there?
Any suggestions?

Thanks
Sono
 

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