Brian, You *could* put the resistor in the mic plug, but I would think it easier to add the resistor in the K2 to the back of the microphone jack between pin 1 and pin 6 as is normally done. In the K3, you simply turn Bias on in the menu.
If you choose to put the resistor in the mic plug, run the K3 without Bias selected, it will pick up the voltage from pin 6 73, Don W3FPR Brian Machesney wrote: > Thanks, Don. > > Not knowing any better, I simply shorted the AF and MICBIAS when I connected > the mic to the K3. From what I can see in the K3 schematics, the only > bypassing on the MICBIAS line is 1uF (rev B, sheet 5 of 7, "Front Panel - > Miscellaneous"). Can I build the same resistor into the mic plug and use it > that way for both the K2 and K3? > > Brian K1LI > > On Fri, Jan 29, 2010 at 9:34 AM, Don Wilhelm <w3...@embarqmail.com> wrote: > > >> 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 > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.733 / Virus Database: 271.1.1/2655 - Release Date: 01/29/10 > 04:08:00 > > ______________________________________________________________ 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
