I have a condenser mic that is not on the list of "known" mics in the docs or on the Elecraft web site. I'm trying to decide whether to simply short the +5V to the AF when connecting my condenser mic to the KSB2, or to place a resistor in between. I am more concerned about potential long-term adverse effects on the mic element by operating it out-of-spec than I am concerned with damaging the K2.
A DMM shows the DC resistance of the element to be 400 Kohms! Not really surprising, I guess, since a condenser mic is electrically similar to a capacitor. The manufacturer specs the mic element at 4.5Kohms and 1.5V to 9.0V bias. Applying the KSB2's +5V directly to the mic element's 4.5K ohms should produce 1mA drain, no sweat for the KSB2, and right in the middle of the manufacturer's applied DC voltage spec. The manufacturer's tech sent me a wiring diagram that shows a +12V supply with a series resistor between 470 and 2.2K ohms to the mic. The 470 ohm resistor would apply nearly 11V to the mic, if the mic element and the series act as a pure voltage divider. The 2.2K ohm resistor would produce 8V at the mic. The KSB2 schematic shows a 2.2uF electrolytic cap between the MIC AF and the rest of the KSB2, so I wouldn't think there's any risk of a short. Help from those in the know, please? -- 73 -- Brian -- K1LI ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
