[AMRadio] D-104 modifications

Jim Wilhite w5jo at att.net
Fri Aug 27 22:22:28 EDT 2010

Not too many years back, a couple maybe, I sent one of my D 104 mics to 
the people who owned the name Astatic, Omnitronics as I recall.  For 
about 48 bucks they replaced the cartridge with an original (according 
to them) and returned it to me for ~$48.

I just did a quick search for Omnitronics and found scads of returns for 
that name and none of the websites that I viewed mentioned Astatic.  I 
wonder if they are still around doing business but, given the niche 
market for these mics,  I wouldn't bet on it.

CB radio and hams are the only people who use(d) them and they have 
saturated both markets pretty well.  For years if I found one at a fest, 
I would take the head to someone with an oscilloscope to see if it had 
output.  I would whistle different tones into the head to see the 
response.  Not very scientific but it gave me an idea whether the mic 
was working.  You never know the quality until it is attached to an 
amplifier.  Maybe the best answer is the Heil Sound replacement 
cartridge these days.

With the original I put a resistor in series with the element to flatten 
the response curve.  Values between 150 K to 500 K would do that.  Then 
run it into a high impedance grid like some have mentioned and you can't 
tell it is a D 104 if the resistor is large enough.


----- Original Message ----- 

On Fri, Aug 27, 2010 at 4:09 PM, D. Chester <k4kyv at charter.net> wrote:

> Why is there a problem securing Rochelle salt? I have heard this 
> elsewhere
> on the net too, but Rochelle salt is not exactly unobtanium. There are
> instructions available for making the stuff at home using every-day
> household chemicals, for example
> http://rimstar.org/materials/piezo/rochelle1.htm I think that story of
> scarcity of Rochelle salt is bogus.

IIRC, it was more to do with their supplier, Don. Either not being
able to supply the quantity, or at all, not being able to find a
replacement supplier. It's been about a decade since it all happened,
so it's kinda fuzzy now. I do recall there was a frenzy when they
announced they would be discontinuing selling replacement cartridges,
but last I knew they had retained some number of cartridges for
in-house repairs only. Send them your mic head and they'd replace the
crystal cartridge and return it for a fee. No idea when or if that
stopped, thought I recall the company was sold at some point.

~ Todd/KAQ

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