[Elecraft] Using a PC headset with K3, connections reverse at rear MIC jack?

[Jim Brown]

On 10/29/2013 8:22 AM, MontyS wrote:
> The rear mic jack is a mono, not stereo, jack.  It will short the ring 
> and sleeve together.

As Iain has noted, this is incorrect. It's a TRS jack that uses only the 
tip and sleeve contacts.

> Audio is on the tip, as is the voltage.

Right.

> The mic should have a blocking capacitor to isolate the audio from the 
> voltage.

Nope. The mic includes a FET line drive that NEEDS the DC voltage to 
operate (the bias).  In general, the value of voltage is non-critical, 
5-8 VDC is in the range, and the voltage is applied through a series 
resistance in the range of 5-8 k Ohms.  That's what's inside the K3, and 
you can use your PC mic with other rigs by making a suitable adapter for 
them wired in this manner.

Every ham rig I've seen manufactured in the past 30-40 years provides 
bias voltage in that range on one pin of the mic jack, and the input is 
DC blocked by a suitable capacitor.

73, Jim K9YC