Using an Airlite-62 headset with a Clansman PRC320 - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 13th Aug 2013, 9:04 pm

Just for reference, I post this. If you want to use an Airlite-62 headset with a Clansman PRC320.

You'll need: A cable "Cordage Assy 5995-99-652-2693" (which is basically a Clansman-style audio-gear plug on about 18 inches of wire) and an Airlite-62 headset with a magnetic-mic insert.
[Note that Airlite-62 headsets can come with a range of different microphones: carbon-insert, magnetic, electret. I can't provide guidance for the non-magnetic-insert type, except to point out that the Clansman audio-gear socket provides access to a +24VDC supply that could be used for biasing an electret or providing DC for a carbon-mic]
Anyway, wire it up as follows:

PRC320 Airlite.
shield--\ /braid
White---------White
\Black
Blue------------Blue
Green----------Green
Red-------------Red
Orange--------Orange

This connects each side of the Airlite's mic-insert to the two "Mic" terminals on the PRC320 (remember that the PRC320 has a balanced-microphone input!) and each earpiece of the Airlite to one of the audio-outputs of the PRC320 and ground.

Note that you'll need some way to activate the PTT: you can either use one of the standard Clansman pressel-switch leads, or do as I've done and fashioned a little diecast box with a couple of Clansman audio-sockets and a flying-lead to the PRC320's mic-socket; in my case this is fixed to the top of the radio by a couple of the threaded mounts where a SURF would fit, and has a toggle-switch to do the transmit/receive switching.

Enjoy!

--G6Tanuki.

QQVO6/40 · 14th Aug 2013, 7:41 am

Hello all.

Good work G6 Tanuki. You have spurred me on towards a new project. Thank you.

This is a handy topic as I have just this week acquired a genuine David Clark aviation headset. Brand new. The most common aviation headsets have high impedance headphones and an electret microphone.
The headset that I now have was made for the American Airforce and it has low impedance headphones and a low impedance dynamic noise cancelling microphone. Just what the doctor ordered. I hope?

I do not want to chop the plug off the headset lead so I bought a "Nexus" brand connector to suit the tip, ring 1, ring 2, sleeve plug on the headset. Wow! Was that ever an expensive decision. Anyway, I have it now so I hope the financial shock will dim with time. My idea is to make up a short jumper lead to go from the "Nexus" connector to a Clansman plug. I intend to use an original curly cord with the PTT switch on the end.
All I have to do is work out the pinout for the Clansman plug.

The Nexus plug is:-
Tip..........mike hot.
Ring 1.....phones hot.
Ring 2.....mike GND.
Sleeve....phones GND.

The Clark headset impedances are microphone 5Ω and the headphones are 10Ω. I am not sure what the Clansman impedances are but I guess I am going to find out.

Just a little side note. Here in Australia we did not use the Clansman range of kit. We ended up with the "Raven" range of radio equipment from the Plessey company. Of interest here is that the same audio lead connectors were used and the Raven stuff is quite interchangeable with the Clansman audio stuff. I have used both. Here the Army fitted an American sourced handset to the Raven system.
Cheers, Robert.

G6Tanuki · 14th Aug 2013, 8:52 am

Hi Robert.

I've heard of Clark Aviation headsets: hadn't realised that they were usually electret mics.

Wiring yours up shouldn't be too hard - at least you have separate "hot" and "gnd" leads for the mic. Much Clansman gear like the PRC320 has a balanced mic input - though it will work with one side grounded it works a lot better if the 2 mic wires are kept isolated from ground.

The Clansman audio-connector also has two audio-feeds - in my case I wired one to each of the Airlite headphones, and commoned the grounds. In your case I guess your Clark headset has the 2 earpieces already wired in parallel so you only have to wire between one audio-out wire on the Clansman plug and gnd.

The typical Clansman audio output level is quite adequate to drive a 5-ohm load: I'm using an external 8 ohm speaker with my PRC320 and though it's not loud it's fine for use in an ordinary room. You may find the level of high-frequency hiss a bit annoying though - small headphone-type transaducers are rather like tweeters and emphasize the high-frequencies. I wired a 4.7uF 250V polyester capacitor across the audio-out lines to give a bit of treble-cut.

BTW I believe the reason Clansman gear has 2 separate audio-outputs and the headsets have the earpieces wired separately, is that in some applications they fed the output from 2 pieces of equipment separately, one to each side of the headset! In tests this was proved to give the listener better ability to discriminate between two simultaneous talkers than just mixing the audio and feeding it to both ears. Kinda like when you can separate out a gabble of speakers at a party on the basis of which direction the sound's coming from.

--G6Tanuki.

13th Aug 2013, 9:04 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Using an Airlite-62 headset with a Clansman PRC320 Just for reference, I post this. If you want to use an Airlite-62 headset with a Clansman PRC320. You'll need: A cable "Cordage Assy 5995-99-652-2693" (which is basically a Clansman-style audio-gear plug on about 18 inches of wire) and an Airlite-62 headset with a magnetic-mic insert. [Note that Airlite-62 headsets can come with a range of different microphones: carbon-insert, magnetic, electret. I can't provide guidance for the non-magnetic-insert type, except to point out that the Clansman audio-gear socket provides access to a +24VDC supply that could be used for biasing an electret or providing DC for a carbon-mic] Anyway, wire it up as follows: PRC320 Airlite. shield--\ /braid White---------White \Black Blue------------Blue Green----------Green Red-------------Red Orange--------Orange This connects each side of the Airlite's mic-insert to the two "Mic" terminals on the PRC320 (remember that the PRC320 has a balanced-microphone input!) and each earpiece of the Airlite to one of the audio-outputs of the PRC320 and ground. Note that you'll need some way to activate the PTT: you can either use one of the standard Clansman pressel-switch leads, or do as I've done and fashioned a little diecast box with a couple of Clansman audio-sockets and a flying-lead to the PRC320's mic-socket; in my case this is fixed to the top of the radio by a couple of the threaded mounts where a SURF would fit, and has a toggle-switch to do the transmit/receive switching. Enjoy! --G6Tanuki.

14th Aug 2013, 7:41 am	#2
QQVO6/40 Hexode Join Date: May 2009 Location: Newcastle, Australia Posts: 321	Re: Using an Airlite-62 headset with a Clansman PRC320 Hello all. Good work G6 Tanuki. You have spurred me on towards a new project. Thank you. This is a handy topic as I have just this week acquired a genuine David Clark aviation headset. Brand new. The most common aviation headsets have high impedance headphones and an electret microphone. The headset that I now have was made for the American Airforce and it has low impedance headphones and a low impedance dynamic noise cancelling microphone. Just what the doctor ordered. I hope? I do not want to chop the plug off the headset lead so I bought a "Nexus" brand connector to suit the tip, ring 1, ring 2, sleeve plug on the headset. Wow! Was that ever an expensive decision. Anyway, I have it now so I hope the financial shock will dim with time. My idea is to make up a short jumper lead to go from the "Nexus" connector to a Clansman plug. I intend to use an original curly cord with the PTT switch on the end. All I have to do is work out the pinout for the Clansman plug. The Nexus plug is:- Tip..........mike hot. Ring 1.....phones hot. Ring 2.....mike GND. Sleeve....phones GND. The Clark headset impedances are microphone 5Ω and the headphones are 10Ω. I am not sure what the Clansman impedances are but I guess I am going to find out. Just a little side note. Here in Australia we did not use the Clansman range of kit. We ended up with the "Raven" range of radio equipment from the Plessey company. Of interest here is that the same audio lead connectors were used and the Raven stuff is quite interchangeable with the Clansman audio stuff. I have used both. Here the Army fitted an American sourced handset to the Raven system. Cheers, Robert. Last edited by QQVO6/40; 14th Aug 2013 at 7:46 am.

14th Aug 2013, 8:52 am	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Using an Airlite-62 headset with a Clansman PRC320 Hi Robert. I've heard of Clark Aviation headsets: hadn't realised that they were usually electret mics. Wiring yours up shouldn't be too hard - at least you have separate "hot" and "gnd" leads for the mic. Much Clansman gear like the PRC320 has a balanced mic input - though it will work with one side grounded it works a lot better if the 2 mic wires are kept isolated from ground. The Clansman audio-connector also has two audio-feeds - in my case I wired one to each of the Airlite headphones, and commoned the grounds. In your case I guess your Clark headset has the 2 earpieces already wired in parallel so you only have to wire between one audio-out wire on the Clansman plug and gnd. The typical Clansman audio output level is quite adequate to drive a 5-ohm load: I'm using an external 8 ohm speaker with my PRC320 and though it's not loud it's fine for use in an ordinary room. You may find the level of high-frequency hiss a bit annoying though - small headphone-type transaducers are rather like tweeters and emphasize the high-frequencies. I wired a 4.7uF 250V polyester capacitor across the audio-out lines to give a bit of treble-cut. BTW I believe the reason Clansman gear has 2 separate audio-outputs and the headsets have the earpieces wired separately, is that in some applications they fed the output from 2 pieces of equipment separately, one to each side of the headset! In tests this was proved to give the listener better ability to discriminate between two simultaneous talkers than just mixing the audio and feeding it to both ears. Kinda like when you can separate out a gabble of speakers at a party on the basis of which direction the sound's coming from. --G6Tanuki.