Using high Z mics with 5V processor chips

[w5hro]

x

[K6IC]

Hi Brian,

K7DYY Bruce's Mic preamp uses a FET front end. The input Z, as seen by the D-104, is 6.8 Meg Ohm, IIRC. Schematic here:

http://k7dyy.com/apsch.htm

FWIW, 73 Vic

[steve_qix]

You could put an FET ahead of the whole thing - a source follower would do it very nicely. It would provide no voltage gain, but would completely buffer the hi Z mic.

Regards,

Steve

[w5hro]

x

[steve_qix]

I have used those chips (the SSM2166P) with high level inputs. I have a circuit which has an input level control (ahead of the chip). You could add a resistor in series with the input (ahead of the gain pot) for additional attenuation.

The SSM2166 is not a real good compressor chip, but it sort of works.

The schematic is at http://www.classeradio.com/mic_preamp_rev_c.pdf