Old military US high impedance headphones
Well I just had some very old headphones put away for me by a freind who was selling them. I came to be interested in them as I have just taken up CW and I was told high impedance sets were almost like a kind of filter, compared to stereo sound system type headphones which I am using at the moment. For £20 its worth a go, and I must admit they look very cool. They look like something that the pilot of a B17 would have worn.....
The high impedance headphones do not reproduce lower audio frequencies well, if at all. "Hi-fi" headphones (generally low impedance) are designed to reproduce the low frequencies as well as higher frequencies. The elimination of the lower audio frequencies reduces the "hum" factor greatly as well as reducing the unneeded noise, etc., that goes along with the received signal.
By the way, World War II headphones are not old! I have a pair of Western Electric headphones with a 1918 date on them! They still work fine.
Thanks for the reply Glen! I am just getting into CW and don't have a narrow filter for my IC718 yet. I was told that just as you say, all of the stuff that I dont really need to be hearing well the old high impedance sets dont reproduce that stuff. At the moment thats all a distraction - its hard enough for me to copy without any other stuff annoying me!
all the best
Double check on the impedance.
Most of the WW2 stuff they used to have in the surplus stores when I was just a stripling lad were 600 Ohms.
I'm not sure if they were Oz made,or Brit or US.
Most of the High Z ones I've seen around were old commercially sold S.G Brown stuff from the UK.
I beleive they are a H32? headset with AMD-H-1 earphones but I could not be 100% sure until I look at them closely again in a few weeks time. I got talking to a CW expert and he was asking how I was going (I have made my first 3 contacts in the last 10 days) and he mentioned a freind of ours had 2 sets of high impedance headphones for sale. So we strolled up to his stall and I looked at them both, and one set was as uncomfortable as anything, but the other set was OK. This looks like them..
I had a set of these phones that I brought back in the early 50’s. They had a larger set of rubber ear pads that covered the entire Ears. (I have big ears) I used them for years on all modes and they were the best phones I ever had. My youngest son plugged them into his guitar amp back in the 80’s and blew them out. It makes me sick because I have never been able to find another pair of phone as comfortable and as clear as them.
Well I picked them up tonight and finally have all the details. The headphones are R14 by Murdock that are 2000 ohms each!!! Its a HB7 headband and very comfy, the rubber earpads are pretty much perfect. The plug is a PL54 so of course doesn't fit my IC718!! I'll do some sort of bodge so I dont wreck the plug and give the headset a try. Hope it works as well as some say it will.
You may need a transformer. Here is an example of a 1000ohm to 8ohm transformer in our nationwide stores. It's about the size of a sugar cube or cm3, and costs about $4. I'm sure you can locate similar.
I think that if you need to go from 2000ohm to 8ohm, that would be a 16:1 ratio or rated at approx. 120v to 8v.
We let Ohms Law take over to find the path of least resistance through the coils
A modern audio amplifier output rated at 8 ohms will drive a 2000 ohm headset, without any damage to either the audio amplifier or headset!
Fair Radio Sales Co. (Lima, OH USA) sells a used JK26 in-line jack that will mate to the PL54 plug.
The headphones are R14 by Murdock that are 2000 ohms each!!! It's a HB7 headband and very comfy, the rubber earpads are pretty much perfect. The plug is a PL54, so of course doesn't fit my IC718!!
I'll do some sort of bodge (adapter cable) so I don't wreck the plug and give the headset a try.
Last edited by W9GB; 04-25-2012 at 10:48 AM.
Nullius in verba