[Elecraft] Balanced Mic to Unbalanced Connection Follow Up Question

[Joe Subich, W4TV]

 > 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 1.

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 1 and 2.
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.

73,

    ... Joe, W4TV


On 2020-06-09 4:49 PM, Tony wrote:
> All:
> 
> I have a follow-up question regarding balanced mics and unbalanced 
> connections. I'm about to connect a balanced dynamic microphone (Heil 
> PR-781) to the rear mic input on my K3S which has a 1/8" unbalanced mono 
> connection.
> 
> One recommendation was to connect XLR pin #2 mic (+) to the tip of the 
> 1/8" jack and pin #3 mic (-) to the sleeve. In this case, pin #1 or 
> ground is left floating with no connection. A 1/8" mono jack was 
> recommended for this setup.
> 
> The other recommendation was to connect pin #2 to the tip and pin #1 and 
> #3 to the sleeve of the 1/8" jack. It was also suggested that I can use 
> either a 1/8" mono or a stereo TRS jack in both cases.
> 
> So which is correct?
> 
> Tony -K2MO
>