View single post by EVPfan
 Posted: Dec 10th, 2014 09:46 PM
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EVPfan



Joined: Mar 15th, 2008
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Hi Jeremy,

have you built this circuit already? What's the input impedance of the first stage? Is it very sensitive to mains hum? Is the 60 Hz notch filter effective? Usually, mains hum has a lot of harmonics, i.e. multiples of the fundamental frequency (120 Hz, 180 Hz, 240 Hz, etc.), which are hard to filter out. This is why I'm using a symmetrical input, so any kind of hum can be canceled out. In my case, this is necessary because of the very high impedance of the inputs (1 MOhms and above). The output of my preamplifier goes into a mixer which has a 2-band EQ.

BTW, better a hole in the wall than a hole in the head...! :blink::biggrin:

Stefan