开云体育

g'luck... most of the original elements have gone bad... a few still
linger.? Caveat Emptor Grasshopper...? An article in ELECTRIC RADIO some
time back showed the use of KOBITONE elements, which WORK SWELL.? I did
a D-104 and it actually sounds BETTER than the working ones I have.?
Sources tell me that the particular element specified in the article
isn't available, BUT... KOBITONE is verry much around and many other
elements will work.? MOUSER used to carry them, but that may no longer
be the case...? so do your own diggin'

Tom - W?EAJ

FWIW, crystal microphones have not been made for many years. Old
ones should be avoided if you want a practical, working microphone. In
some cases ceramic versions were made with similar performance, these
have a much better chance of still working.
Rochell salt crystal elements for microphones and phonograph pickups
(also headphones and disc cutter heads) were introduced c.1933. The
original patents were owned by Brush Development company, who licensed
many others to manufacture them. Crystal elements have the virtue of
very high output and good quality sound at economical prices, so they
were very popular. However, they are very vulnerable to high
temperatures (much over 100F), moisture, mechanical shock (dropping or
scraping a pickup across a record), and where used as motors (headphones
and cutters) to mechanical shock from being over driven. The greatest
problems are exposure to high temperatures and entry of moisture. There
were several patented methods of protecting the elements from moisture
(Astatic called their Metalseal) but they develop leaks and the crystals
turn to mush (literally).
Crystal elements can not be tested with an ohm meter, they look
like capacitors and do not pass DC. If you measure any resistance the
element is probably dead.
Many of these mics are classic designs but should be seen as
collector's items and not usable.
The D-104 was the first crystal microphone sold commercially (I
think 1933). While a flat frequency response version was available early
on the rising response version became the more popular. The response is
exaggerated by operating it into too low an impedance, ideally, they
should work into an infinitely high impedance, however the response of
the D-104 is tailored for speech by means of resonances in the mechanism
and the large disc shape which results in additional rise due to
diffraction.
The elements can be replaced with others, which will preserve the
effect of the diffraction, but the internal resonances may not be the same.
The output level of a D-104 is one of the highest for any
non-amplified microphone. The high output for the mics and phono pickups
was high enough to often eliminate a stage of amplification, a great
economy in the vacuum tube days when amplification was expensive.

--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998

We all used the Kobitones 20 years ago. They are all long gone.? I have a personal stash of them and am running low.. I have lost five D104 elements in the last 5 or 6 years. I ran them on six different stations here.? They just up and die. Nothing happens. They just die.?

Lots of OM's purchased 10 and 20 of them, only to have them end up in a dump when they went SK.??

There is nothing on the market that works properly.? Installing an electret element in a D104 should be a felony offense.

C