Early 1970's, Amplivox (a RACAL UK company) releases a headset touted as one of the lightest professional headsets, their target market was the aviation industry and military.
I grew up with this headset, provided to me by a friend who was in the NZ Air Force for a "look see" from a technical perspective. These headsets were quite something way back then, no closed ear muffs or long stick mics - electronic miniaturisation had begun! This was the early 1970's ...
Then along comes the American film industry in the late 1970's which took a shine to these headsets as props in extremely well known productions (Star Wars etc) and the Amplivox Minilite became the "holy grail" for movie prop collectors.
My interest in this headset was purely from a "vintage electronics" perspective, I am not a collector of movie memorabilia but I like to look at how older products were designed and put together, especially when it involves companies such as RACAL - designers and manufacturers of superb commercial and military communications systems.
Please read the FULL description below, I describe the Minilite in great detail (and also give you a look inside!) but there is one very obvious thing wrong with this headset - NO HEADBAND!
So, to actually use this headset you will need the headband (plastic based, not metal) I have been unable to find it, lost in the passages of time!
RACAL Electronics - Amplivox Headset (Incomplete)
Released in 1971
Designed for professional use, rugged construction.
Two separate sections, housed in special high impact plastic. Secured by special bolt/sockets on each side of the housing
TOP SECTION:
Microphone is inside the housing, element type is piezo (crystal) and it is encased/suspended in a rubber "bowl" with a short rubber hollow tube which fits into the flexible exernal microphone tube/filter near the users mouth. The external flexible tube is 100mm long, ending in a rubber mouthpiece (to gather soundwaves) with an integral filter. There is no microphone element exposed to the user spitting while they talk! The wires for this microphone element are white/white-green to the tiny terminal board and then yellow/green & blue down the cable to the in-cable amplifier/switch housing.
The external microphone neck is flexible and removeable (unscrews)
Earpiece is sitting at the end of a swivel base chromed metal shaft, the wires (white & black-grey then after the tiny terminal board, white & black) for the earpiece run up inside this metal shaft.
Both the earpiece & microphone are piezo (crystal) based (not dynamic), high impedance - *** more about this in the TESTING section below.
Construction standard of the whole top assembly is very high and obviously made to endure the vigours of tough environments.
IN-CABLE SECTION (SWITCH & LEVEL)
230mm along the cable from the top section is a small signal amplifier for the microphone and a special SPDT toggle switch. The audio amplifier has discrete components, 2 transistors (one is a common BC 109 metal and the other I cannot read the type number). There is a PCB mounted level adjustment pot which is externally accessible by the user, screwdriver adjustment only.
The switch operates as locking in one direction and the other direction it stays in position only while the user is pushing the toggle. This is the "push to talk" switch.
The earpiece connections go straight through this housing, no changes to the signal up to the earpiece.
LEAD & PLUG
The lead from the switch/amplifier housing is 1.2m long, where it is terminated with a special 5 pin male connector. I cannot find any meaningful ID on this connector (except a very small (tiny) 33 stamped into the plug body with a graphic design around it) but I strongly suspect it is a LEMO product (Germany). Although there are 5 gold plated pins, only 3 are used with the remaining two never having any connection at all (unsoldered) With only 3 wires going up the cable (including the earth/ground/shield) this must mean that the power for the small signal amplifier is supplied using phantom technology (like a condensor mic). See my testing below ...
COSMETIC CONDITION:
Excellent condition, no broken parts (or even stressed!)
The rubber fittings (earpiece and microphone) are in excellent condition - surprised me after 50 years, I would have expected to see just some degradation but these items are clean and no signs of any ageing/perishing.
Comes WITH the original Amplivox carry pouch! The zipper still works and there are no tears. Nice and clean too but the gold stamped printing has worn off a little.
All items (top section, switch/amplifier etc) have clearly stamped into them AMPLIVOX MINILITE MADE IN ENGLAND - this is genuine product not a 3rd party knockoff, which apparently became commonly available due to the film buffs wanting to get their hands on these things.
The most obvious missing item is the headband. Nothing on the housing has broken, the headband has not "broken off" but the headband (plastic) fits underneath the chrome clip you can see on the top section - someone has removed it and it is now lost in the anals of time!
TESTING:
It has been a LONG TIME since I have played around with this headset, it goes back to the days of my youth! Just for interest sake I connected a low level sound source to the wires feeding the earpiece - all great!
I then experimented a bit with the microphone side, using a mic amplifier here that provides low voltage phantom power up the cable along with audio coming down. Most phantom power supplies are 48V so watch out, just to be cautious if you use one of those. I used a special 12V phantom supply. Again, I was able to hear audio from the microphone, pretty narrow band (it is intended for communications speech afterall) - impressive! After 50+ years this headset STILL performs well, just such a shame about the headband.
Since testing the taking the photos, I have now placed the whole kit into sealed plastic to keep it nice and dust free.
So whether you are into OLD aviation/military related communications accessories OR a film buff who likes to have some of those props hanging on your walls, this Amplivox is calling out to you!
