[Elecraft] Balanced Mic to Unbalanced Connection Follow Up Question

[Bob McGraw K4TAX]

I use a Shure SM-58 mike with my K3S. It is a balanced dynamic mike.

It has an XLR at the mike and the 8 pin Foster connector at the radio.  
I use good quality, 2 conductor, shielded mike cable.

It is wired as follows:

XLR pin #1 to Foster pin #8  {shield}

XLR pin #2 to Foster pin #1  {black}

XLR pin #3 to Foster pin#7 {white}

Operating 160M - 6M at 500 watts or less, I find no issues with the 
wiring convention as it works very satisfactory.

73

Bob, K4TAX



On 6/11/2020 8:15 AM, Rich wrote:
> Interesting stuff here.   Since the original post was regarding the 
> Rear Mic jack.   Would this method also be recommended for the Front 
> Panel Mic Jack also?
>
> My guess is yes
>
> Rich
>
> K3RWN
>
> On 6/9/2020 22:50 PM, Don Wilhelm wrote:
>> Joe,
>>
>> I did not say anything to the contrary.  The 'dongle' that I was 
>> referring to is the connection to pin 1 which should be connected to 
>> the outside of the K3/K3S enclosure.
>>
>> 73,
>> Don W3FPR
>>
>> On 6/9/2020 9:13 PM, Joe Subich, W4TV wrote:
>>>
>>> On 2020-06-09 8:14 PM, Don Wilhelm wrote:
>>>> So --- make an adapter so that pins 2 and 3 are connected to the tip
>>>> and ring of the mic jack,
>>> No, no, no!  The ring of the K3/K3S rear panel mic jack *IS FLOATING*.
>>> Pins 2 and 3 of the XLR *MUST BE* connected to tip and *SLEEVE*.
>>>
>>> 73,
>>>
>>>     ... Joe, W4TV
>>>
>>>
>>> On 2020-06-09 8:14 PM, Don Wilhelm wrote:
>>>> So --- make an adapter so that pins 2 and 3 are connected to the 
>>>> tip and ring of the mic jack, then add a one wire 'dongle' exiting 
>>>> from the XLR plug that is connected to XLR pin 1.  Connect that 
>>>> wire to a screw on the chassis of the K3/K3S/KX2/KX3.
>>>>
>>>> Noise, hum and buzz are  then conducted from the shield onto the 
>>>> "outside" of the radio enclosure where it should be - avoiding the 
>>>> "pin 1" problem that K9YC often refers to.
>>>>
>>>> For those not familiar with the "pin 1" problem, it is caused by 
>>>> the jacks in the transceiver (or other gear) being connected to the 
>>>> circuit board ground plane where it can couple into sensitive 
>>>> circuits and cause coupling problems. Proper bonding between 
>>>> enclosures following the path of audio or coax lines can minimize 
>>>> that problem by keeping some of the noise, hum and buzz mostly on 
>>>> the outside of the enclosure rather than injecting it into the 
>>>> circuits on the board ground plane.
>>>> We did not have this problem when we mounted the jacks on the 
>>>> enclosure rather than mounting them on the boards, usually isolated 
>>>> from the outside of the enclosure.
>>>>
>>>> 73,
>>>> Don W3FPR
>>>>
>>>> On 6/9/2020 7:47 PM, Joe Subich, W4TV wrote:
>>>>>
>>>>> Correcting *ALL* the typos <G> ....
>>>>>
>>>>>
>>>>>> So which is correct?
>>>>>
>>>>> They are electrically equivalent.
>>>>>
>>>>> Pin 2 of the XLR connection is Mic+
>>>>> Pin 3 of the XLR connection is Mic-
>>>>> Pin 1 of the XLR connection is the cable shield (ground).
>>>>>
>>>>> Mic audio is present between pins 2 and 3.
>>>>>
>>>>> Pin 1 is nothing more than a shield and should be independently
>>>>> connected to the *chassis at the jack*.
>>>>>
>>>>> Good quality XLR cables use a *TWISTED PAIR* for pins 2 and 3.
>>>>> That twisted pair is shelf shielding - particularly good for
>>>>> rejecting hum. Connecting a shield in parallel with the wire
>>>>> for pin 3 "unbalances" the twisted pair and makes it much
>>>>> more susceptible to hum and RFI - particularly when the shell
>>>>> of the 3.5mm plug/jack is not tied to the chassis/case of the
>>>>> transceiver.
>>>
>>>
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