Telex Airman 750 headset wiring and settings for K3

[OE5CSP-Chris]

Elecrafters,

Is anybody using the Telex Airman 750 headset with the K3?
I soldered the blue microphone cable to the tip and the white cable  to the other ring and turned on BIas.
While monitoring the signal in test mode I can hear strong strange sounds similar to the ignition of a spark plug?
Any thoughts?

vy73,Chris-OE5CSP