[Elecraft] D104 mic

[Jim Brown]

On Fri, 9 Jul 2010 20:47:36 -0400, Tom W8JI wrote:

>It will sound great if you add a J310 or similar JFET source follower. 

Hams spend WAY too much time hand-wringing about impedance matching in 
audio circuits. Audio circuits have not been impedance matched for 
nearly 50 years! As long as the input Z of the preamp is not so low 
that it loads the mic severely, everything should be fine. The input Z 
of the K3 mic circuit is on the order of 10K. That's pretty high, and 
most mics ought to be quite happy with it. 

For a passive mic, the downside of excessive loading is usually some 
modification of the frequency response, some loss of level, but no 
distortion. TXEQ can easily fix any response problems, and the K3 has 
plenty of mic gain to make up for any loss. 

Tom's advice is solid if it's a VERY high Z mic, BUT it may also depend 
on the version of D104 that you have. I haven't played with a D104 for 
nearly 40 years, so don't know enough about that to have an opinion 
that matters. :) I would first try it straight into the K3 as Hank did, 
adjust levels per Elecraft intructions, then get someone with good 
audio ears to talk you into TXEQ settings on the air. If you can't make 
it sound right, then follow Tom's advice and build the follower 
circuit. 

73, Jim K9YC