[AMRadio] Mic to use with class E transmitter

[Donald Chester]

>From: Dino Darling <k6rix at arrl.net>

  I really
>like the D-104 but not too fond of the sound quality.

I use a homemade two-channel audio mixer and combine the outputs of a D-104 
and an old Electrovoice dynamic microphone.  I use pre-emphasis with the 
D-104, boosing the highs, starting from about 800 Hz and levelling off at 
about 2000 Hz, at about 10 dB.  I generally use a low-pass filter to cut off 
the highs, either very sharply at 3400 Hz or more gradually, in the vicinity 
of 5 kHz, although  I can switch out the filters and run flat audio beyond 
11 kHz.

The two microphones have to be in phase, of course, so I have a phase 
reversing switch on the dynamic, which is convenient since it runs 150 ohms 
balanced line to a transformer.

My mixer is tube type, the basic circuit designed after one that has 
appeared in the RCA receiving tube manual for decades.

I built this preamp in the mid 70's, and it has worked so well that I am 
still using it with the same microphones.  I have tried other, much more 
expensive microphones, and everyone told me the 2-microphone combination 
sounded better with my voice.

I have had ham visitors in the shack, and people said they sounded better on 
  their own stations than on mine,  but when I got on the mic, they said the 
quality was excellent.  I suspect I stumbled on a combination that is ideal 
for my voice characteristits, but not necessarily for others.

Don K4KYV

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