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Saturday, July 8, 2017

Stop Me Before I Commit an Electronic Atrocity!

Sadly, not mine
I like the D-104 mic.  I bought one from Astatic shortly before they went under and it has provided good service with many different rigs for a long time.

I wanted another one, primarily for my DX-100/HQ-100 station.  I saw one on e-bay and a few days later it was here.  Unfortunately the seller was correct when they warned that it showed no output.  I had hoped it was a problem with the amp in the base, but no, it seems that the crystal element is quite dead.  It is an MC320 cartridge marked 7-77.  There is an aluminum sheet at the front that is apparently supposed to be riding atop a center support that connects mechanically with the magic crystals.  But it looks like a circular tent that has poked through the center support and collapsed around it.

Just a few years ago there were some options for replacement elements, but it seems that most of these are gone.  Bob Heil does have a dynamic element replacement kit for about 68 bucks. 

There are many schemes for putting electret elements in the old D-104 head...  I was reaching for the junk box but I stopped myself.  NO!  I will try not to commit this kind of electronic barbarity. (I have already sinned by killing several QF-1 Q multipliers and a couple of Benton Harbor lunch boxes.)  I will instead turn to the SolderSmoke brother/sisterhood and ask if anyone out there has a crystal element that could bring this old mic back to life.  My DX-100 deserves nothing less. 

Anyone have a D-104 crystal element in their junk box? 


  1. I always wanted to try building the KT4QW condenser microphone from December 2003 QST:


  2. You could always try re-gluing the center post. Had luck with that once. I also have a new, in the bag crystal element that is smaller than the 104. It is about 1.5" with smaller 1.25" back. Had them since the 90s.

    I remember having a couple of 104 elements but they could be bad as well given their age.


  3. I'll throw in my $.02 and suggest looking for a 10-D or DA head.

  4. Crystal Mic inserts were quite common until the mid 70s in 'less expense' microphones, even in the entertainment field. While they were generally considered 'second rate' (at best) they were common (I used to repair equipment in my teens. There must be some lurking in junk boxes somewhere. While not original, one would be closer than changing to an Electret.

    (We 'met' when you delivered a lecture at the RSGB convention via Skype.)

  5. If you are looking for a cheap solution, Kobe tone makes a small crystal element for less than $2. Cut a piece of heavy cardboard the same size as the original D104 and superglue the element to the cardboard. Add some Styrofoam filler to make it all snug. Reconnect the wiring and reassemble and talk up a storm.

  6. What may work very well here is a the mic element from a GE or Moto mobile radio. These are the right size to fit and the response could not be more perfect. They are from major suppliers and are spec'd for voice radio communications. Nothing sexy and a violin will sound like crap, but exactly the right mojo for a homebrew radio. Easily found for a buck or two at a hamfest. If you pay more you need to sharpen the haggling skills.
    73, Dave VE3EAC

  7. Not communications, but still audio: the first 'push-button' phones sold by NZPO/Telecom as the fist Digital exchanges came into service here were called 'Pert-phones'. They used a ceramic disc to 'transduce' the 'ring' energy (16.66 Hz) put out to ring the bells (~60V at the exchange, less by the time it got to the instrument). I had an acoustic guitar that I wanted to 'electrify', so I fitted a 'Shadow' unit. It failed, so I investigated, finding it had the same structure and surface, so I just hooked the 'phone insert to the guitar's socket with a bit of audio co-ax and went to it - perfect! Same has now been applied to the mandolin. Just have to try a few places on the body to find the 'sweet spot' and you're away. I'm thinking the same might do for the D-104 - music-quality, no less!

  8. Sorry, "-60V" should have been "~60V". Both AC and approximate :)

  9. It's not my eyesight, it it blogspot or my browser not able to handle the 'squiggle' (tilde) character (shifted top-left key)?


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