In a message dated 00-09-05 23:35:01 EDT > "Bob" K4TAX wrote:
<< Ahh, the 47 ohm resistor looks like a short to the electret element.
Current is not an issue, polarization voltage is an issue. Also,
impedance is an issue. The original 10K provides a much higher Z
impedance when one considers a power supply source as near 0 ohms. >>
In the 1201 kit manual, TenTec specifies changing the
10k down to 470 ohms for the purposes of guaranteeing adequate current to the
entire 1201 microphone circuit; which includes electret mic bias, TL061
op-amp supply current, and several milliamps to power the LED in the
microphone base.
Total of about ~5 milliamps.
You will never get that from 10k and a 8.5 VDC supply ---
The most you could ever get from 10k and a 8.5 volt supply is: 8.5/1e4 = 850
microamps.....
A bit lean ....
- Phil KF6ZZ
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