[Elecraft] Using GM-5 Mic with K2

[Joe Subich, W4TV]

> Thanks, Joe. It seems to me that a 5.6K resistor between pins #1 and
> #6 on the K2 front panel mic connector would create bias on the pin
> #1 mic line that would carry over to GM-5 pin #1 mic line.

Yes, if you have bias on pin 1 it will appear on the mic.  You did not
ask that question - you asked if pin 6 was connected in the CC-1K.

> I am looking for a way to use the GM-5 as well. I am going to somehow
> have to eliminate bias from pin #1 when I use the GM-5. I think I
> might be able to do this by connecting the 5.6K resistor between pins
> 5 and 6 on the K2 front panel mic connector and connect pins 1 and 5
> together on the electret mic plugs.

The 5.6K resistor is a user option:
   1) you can remove it to eliminate the bias for the GM5
   2) or you can add a 1 uF cap in the CC-1K - in series with pin 1 on
      Foster end or in series with pin 2 on the XLR end.  I'd suggest
      checking pin 1 to pin 2 for a DC connection but the information
      I have suggests that there is no capacitor in the Heil cables
      for Yaesu or Kenwood - my information is that only the CC-1I
      has a blocking capacitor.
   3) you can install 5.6K resistors between pin 1 and pin 6 in the
      mic connectors on your electret mics.
   4) you can check to see if there is DC continuity between pin 1 and
      pin 2 of the GM-5.  If Heil has done it right they have installed
      a 1 to 10 uF cap in series with pin 2 of the GM-5 (pin 1 = mic
      return/shield, pin 2 = mic "hot", pin 3/4 = PTT switch) to block
      DC.

73,

    ... Joe, W4TV



On 8/16/2011 5:24 PM, Roy Morris wrote:
> Thanks, Joe. It seems to me that a 5.6K resistor between pins #1 and #6
> on the K2 front panel mic connector would create bias on the pin #1 mic
> line that would carry over to GM-5 pin #1 mic line. This resistor is
> needed to supply bias for the MD2 and MH2 electret mics. I am looking
> for a way to use the GM-5 as well. I am going to somehow have to
> eliminate bias from pin #1 when I use the GM-5. I think I might be able
> to do this by connecting the 5.6K resistor between pins 5 and 6 on the
> K2 front panel mic connector and connect pins 1 and 5 together on the
> electret mic plugs. This should keep bias off the GM-5 if pin #6 is not
> used with the CC-1K.
> The only problem I see is that pin #5 is a function line and in effect
> is a floating ground.
>
> ----- Original Message ----- From: "Joe Subich, W4TV" <lists at subich.com>
> To: "Roy Morris" <w4wfb at carolina.rr.com>; "Elecraft Reflector"
> <elecraft at mailman.qth.net>
> Sent: Tuesday, August 16, 2011 4:45 PM
> Subject: Re: [Elecraft] Using GM-5 Mic with K2
>
>
>>
>>> I would like to know if the CC1-K cable connects the 5v on pin #6
>>> from the K2 to pin #6 on the GM-5 creating an unwanted bias.
>>
>> No.
>>
>>> There is a 4 pin mic connection on the CC1-K the GM-5 plugs into.
>>> Does one of these 4 pins supply bias to the GM-5?
>>
>> No. The fourth pin is PTT.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 8/16/2011 4:06 PM, Roy Morris wrote:
>>> I would like to know if the CC1-K cable connects the 5v on pin #6
>>> from the
>>> K2 to pin #6 on the GM-5 creating an unwanted bias. There is a 4 pin mic
>>> connection on the CC1-K the GM-5 plugs into. Does one of these 4 pins
>>> supply bias to the GM-5? Thanks, Roy W4WFB
>>>
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>