[Elecraft] K3: Heil PR20 Microphone

[Don Wilhelm]

Howard,

The problem may be your microphone cable wiring.  I will try to cover 
the three possible cases I know about for connecting a balanced mic to 
an unbalanced input.

The Heil PR20 microphone uses an XLR connector to connect to the mic 
cord - two balanced  wires on pins 2 and 3 plus the shield on pin 1 
(standard wiring for pro-audio).  How are you connecting the two wires 
to the K3?  One of the wires must connect to ground and the other to the 
AF input.

If you are using the front connector, one of the two wires connects to 
pin 1 and both the shield and the other wire connects to ground (pins 7 
and 8).
If you are using the K3 rear connector and you have wired your own plug, 
one of the wires must connect to the tip of the plug and both the other 
wire and the shield must connect to the shell.  If it is a stereo plug, 
nothing is connected to the ring.

If your mic cable has a 1/4 inch TRS plug on one end (a common pro-audio 
cable), and you used a 1/4 to 1/8 inch stereo adapter, it will likely 
not work (out of the box).  Open the adapter (or the mic cable plug)  
and connect the ring to the sleeve.  If you used a 1/4 inch stereo to 
1/8 inch mono adapter, then it is wired wrong for your application - 
both sides of the mic element wires are connected together in the 
typical stereo to mono adapter, and will not work.

In other words, the K3 wants unbalanced AF input and your microphone is 
for balanced operation.

73,
Don W3FPR

On 9/13/2011 10:03 AM, Howard Ashcraft wrote:
> I purchased a Heil PR20 microphone after comparing sound quality with
> several other options.  To my ear, it had a nice combination of clarity and
> fullness.  However, I am getting relatively low output from the mic and
> consequently low drive to the K3/100.  With the microphone configuration on
> "hi" and with gain advanced fully (60), I have to speak fairly loudly to
> drive the K3 to 60 watts measured on an LP100 wattmeter.  Power output on CW
> is the full 100w plus a little.  I could design a small pre-amp stage to
> boost the gain, but am wondering if I am overlooking something (or is it
> common to use a  pre-amp for this type of mic?)  Howard W1WF
>