On 7/19/06, Dumitru Stama wrote: > > Because i didn't know how to make it. After two days of having the > op-amp in my head and google in front of my eyes i think a bandpass > filter is the answer. I re-made the schematics and a new eagle library > containing TL072 since i could not find it in the official suite nor > on the cadsoft site. > http://electronica.asm.ro/electret/scope.html > After removing the 10nF compensating caps and putting 100pF ones > instead the circuit works very well and the gain can be seen. Now i > have that mic-noise problem :) Since nobody is buying my noise-cancels hypothesis, why don't you split R1 into two 10k in series. Then put a cap from their junction to ground. This will filter the supply voltage to the mic. Regards, Mark markrages@gmail -- You think that it is a secret, but it never has been one. - fortune cookie -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist