[Elecraft] Balanced Mic to Unbalanced Connection Follow Up Question

[Rich]

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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