[Elecraft] Microphone Wiring

[lew]

Am using a Super Combo Keyer II by ZS4TX where the audio out  from that 
box has pins 1 and 6 connected to the output of a 600 ohm 1:1 
transformer with pin 1 being decoupled with a 10 microfarad 
non-polarized audio capacitor. This looks like pin 1 then is the audio 
source and pin 6 is a floating audio ground.
The question is do I use this pin 6 as my ground for pin 7 or 8 for the 
K3 mike connector or would any old ground work for pin 7 and/or 8 for 
the Elecraft?
   Thanks,
    Lew   W7EW/W7AT
#1560/1561