What ever happened to the idea of making ones own mike cables? Two
connectors, plus a length of 2 conductor shielded cable and a bit of
careful soldering, specially on the Foster plug. Just use a good
quality XLR connector such as Cannon or Neutrik. It isn't "rocket
science" and it is much less expensive than buying an expensive cable
plus and adapter and trying to figure out why it doesn't work. All of
the drawings and information is in the manual. And for less than $10
you will have a good quality working cable which is the exact length you
need and a project for which you'll be proud.
If you don't feel you are able to do this, then check with some of the
members in your radio club.
73
Bob, K4TAX
On 2/11/2019 6:39 PM, Robert Rennard via Elecraft wrote:
Chuck, KE9UW wrote =
// You cannot use Heil's adapter for the front panel Foster 8 pin connector on
the K3s because they short the ring to the sleeve for some unknown reason. So
in order to use the K3s front panel 8pin Foster socket, you need to make your
own Foster to stereo mini phone connector adapter. Only two connections and DX
Engineering has an excellent Foster plug. Ignore the reference to Heil
Replacement Part, it's just the same old Foster 8 pin plug for all mics and
rigs. //
The PC standard is for electret bias to be supplied to the tip and ring of a
tip, ring, shield (TRS) connector with audio from the microphone entering the
PC on the tip. The around 8 vdc bias is to be supplied via isolating TWO
resistors, one to the tip and one to the ring.
Low budget USB soundcard adapters use ONE resistor supplying bias voltage to
both the tip and ring which are thus shorted together within the adapter. My
Heil ProSet 3.5 mm microphone plug has no ring, just an extended sleeve. So,
essentially the Heil microphone plug has the ring and shield shorted together,
and the cheap USB adapter shorts the tip and ring, so inserting a Heil
microphone plug results in the tip, ring and shield all being shorted together.
The microphone would get no electret bias, and the audio it can’t produce is
shorted to ground, too. On the other hand, good PC soundcards use TWO
resistors and the Heil ProSet works fine with them!
I believe in trust but verify. Chuck is correct, plugging a TRS aka stereo
jumper cable into the 3.5 mm microphone jack on my K2/K3 Heil adapter and
checking things with my Fluke DVM reveals that somewhere in the adapter the
ring and shield are shorted together; maybe in the way things are wired, may be
in the Foster plug.
Continuing, with the K3 MIC-SEL sent to RPL-BIAS, at the rear-panel connector
relative to the shield there is 7 VDC of bias applied to the tip, and the ring
seems to float. With power OFF, the resistance between tip and shield was
about 4.5 megohms and between the ring and shield even higher.
Thanks Chuck, I learned something. It was a good day.
Bob R – N7WY
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