In a message dated 00-09-04 09:33:09 EDT, you write:
<< Have you checked the voltage to the mic from your Corsair 2 ?
I think the 201 manual says that the Corsair-2 is supposed to work fine with
the mic, but it might be worth a simple voltage check anyway. >>
Yes, the voltage from the Corsair is a good solid 8.5 volts DC. One of the
first things I did when I bought the CII was to jumper the 10k resistor on
the AF board with a 47 ohm resistor to provide plenty of current at the mic
connector for any external mic I might be using.
And it worked fine with other mics I have here.
I have had a fair amount of experience designing low-level preamps for
electret mic elements, and have always found that the electret element needs
to be biased with less than ~ 5 to 6 k to achieve adequate output. Usually
1~3 k is about right. The 22k bias resistor in the 1201 mic is ten times too
large.
Another few changes I didn't mention, but oughta be put in as well ---
the top of C1 should be moved to the other side of L1 ( for better RFI
filtering ); and --- it wouldn't hurt to add a ~ 10 uf cap on the 'M+ red
line'
( input power ) for decoupling ( just good engineering practice ).
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