Using high Z mics with 5V processor chips

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Using high Z mics with 5V processor chips

Postby w5hro » Sat Jan 11, 2014 5:57 pm

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Last edited by w5hro on Sun Jan 19, 2014 8:45 pm, edited 1 time in total.
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Re: Using high Z mics with 5V processor chips

Postby K6IC » Sat Jan 11, 2014 10:21 pm

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
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Re: Using high Z mics with 5V processor chips

Postby steve_qix » Sat Jan 11, 2014 10:35 pm

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
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Re: Using high Z mics with 5V processor chips

Postby w5hro » Sun Jan 12, 2014 4:02 am

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Re: Using high Z mics with 5V processor chips

Postby steve_qix » Wed Jan 15, 2014 12:23 am

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
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