Brian, Is that a 3 terminal mic element? If so, then you can follow the manufacturer's instructions and apply the 5 volts to the voltage terminal on the element. OTOH, most of these elements are 2 terminal, and the voltage should be applied to the AF pin through a resistor - try 5.6k like the Elecraft MH2 uses as a first trial, it will likely work because the resistance is not critical. If you try to connect the 5 volts directly to the AF terminal, you will effectively bypass all the audio to ground. For AC signals, a power rail is jst the same as ground because there are large bypass capacitors on the voltage rail.
73, Don W3FPR Brian Machesney wrote: > 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? > > ______________________________________________________________ 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
