MR> 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 :) MR> Since nobody is buying my noise-cancels hypothesis, why don't you MR> split R1 into two 10k in series. Then put a cap from their junction MR> to ground. This will filter the supply voltage to the mic. No problem, i don't think that by doing this i will do any harm since is just filtering of the power supply -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist