Electronics > Projects, Designs, and Technical Stuff

Military Microphone Amplifier - Amazing Old Tech

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willeye:
Got hold of 2 of these amazing little boxes. Both Labelled 608/1/33746 Microphone Amplifier. Not sure exactly what they were used in but they look so nice. I have just built with the help of the beginners forum a condenser mic pre-amp and then i spotted these and thought the looked interesting.

They seem full of very spiffy components and the op amps look top spec.

Starting to reverse engineer them but I thought you guys might like a look too. Anyone know anything about this sort of kit? I cant find anything on them online, just need to work out if i can use them for anything interesting.

james_s:
I don't see anything to suggest military. Those look like they were hand made, some sort of very low volume custom production for some specific application. It's hard to say what they were built for but the construction reminds me of some doppler ultrasound devices for checking the blood pressure of pets that I've repaired, same sort of PCB that looks like it was built in some guy's garage. The LM301 is a rather mundane op-amp, not something I'd call "top spec", if I recall correctly it's inferior to the lowly LM741.

willeye:
They came from ebay and the listing stated "2 identical microphone amplifiers taken out of military test gear. Both are in full working condition. operate from 24v DC

not sure of gain or pin out. "

Thats why i think they are military.

james_s:
What is "military test gear" though? They could be custom test gear hand built by a technician in the military to test something else. They certainly are not the sort of thing you'd find in actual military hardware, ie installed in tanks or airplanes or whatever. It's possible they were part of a bench test rig for checking headsets or other comm gear. 

At any rate they probably work just fine as microphone pre-amps, but I wouldn't expect any kind of spectacular performance, they're made with very early op-amps.

phil from seattle:
socketed dips are definitely not military, at least anything that would be in the field.  Given audio frequencies, they really don't need high spec opamps, though. Also, the military would have used LM101 or maybe LM201 which have a wider temperature spec.  The 301 is only rated down to 0C.

By the way, the NatSemi data sheet for that is a great example of how datasheets should be.  Makes me nostalgic.

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