High impedance headphones.

[Andrew B]

Apart from the offerings on various auction sites, high impedance headphones of any type or repute seem to be extinct or made from unobtainium.

I have seen it suggested that standard (even multicolored) low Z headphones in conjunction with a common transistor-type output transformer work almost as well in crystal radios and basic 1 or 2 valve radios.

Does anyone have experience of using low Z's and a transformer or am I to persevere in looking for the elusive high Z headphones?

Andrew

[Station X]

My own experience is that low impedance headphones work fine with crystal sets. Apparently they affect the 'Q' of the tuned circuit though.

You wouldn't want to wear some vintage headphones for long. They're very heavy.

[G6Tanuki]

I've used a "LT44" driver-transformer in the past.

Primary to the xtal receiver's output - with a 1000pF capacitor in parallel as a RF bypass.

Secondary - connects to modern 32-ohm stereo headphones OK. You can experiment. Connect the centre-tap of the transformer to the headphones' jack-plug body and the 2 outer ends of the transformer to the phones' tip/ring, or strap the tip/ring together and feed them from one of the transformer's outers with the body connected to the centre-tap, or do the same but with the tip/ring to one outer and the body to the other outer...

Play around and see which gives the best volume! I have a cheap (£5) set of "Vivanco" headphones here that work surprisingly well.

[Andrew B]

Good feedback, I like it on this forum because it's very active, full of "age experienced enthusiasts".

I was looking to go the transformer route as many circuits use the Hi-Z as the anode load and a low Z would not present the correct load.

I am a mere 57 years old, most of the things I learned about valve technology were from messing with >old stuff< aged 11 and for the last 20 years, catching up on valve technology. Many things still puzzle me with regards to valve gear but instead of asking, I study the posts.

Andrew

[greenstar]

Hi Andrew, if you go to a radio rally (check out the RSGB website) or one of the BVWS events you can pick up a pair of high impedance 'phones quite cheaply. You may need a couple of attempts, but myself, I really like the old headphones as items themselves. http://rsgb.org/main/news/rallies/
Or I have heard of folk using mains transformers, the sort found in small plug in power supplies - I think the ones that deliver more current are better. You can also make high z phones from piezo transducers - there is lots of information on this on the web. http://makearadio.com/misc-stuff/piezophones.php

[russell_w_b]

Originally Posted by Station X

My own experience is that low impedance headphones work fine with crystal sets.

DLR5 low-impedance headphones worked well enough on the few crystal sets I've made and have sensitive, rocking-armature movements in the earpieces.

S.G. Browns 'Type F' or Ericsson 2000 Ohm headphones used to turn up at radio rallies (they were always relatively expensive on the surplus market, even pre-eBay days, I found).

I once had a pair of 'Altai' headphones advertised as high impedance, and they turned out to be 8-Ohm units with a step-down transformer in the point where the wires split.

[Diabolical Artificer]

I offered some S G Brown Type F headphones in good condition a while back- no takers. They're gathering dust in the shed. Drop me a PM if you want them Andy#1

Andy#2

[dseymo1]

Crystal earpieces still seem to be available, and work well with crystal sets.
No reason why you couldn't convert a pair of cheap dynamic phones to take the xtal inserts, or, for that matter, piezo sounders.

[Biggles]

I too have used the LT44 transformer to match low impedance phones successfully . I have also used a pair of higher impedance telephone type earpieces to good effect. I made some headphones out of these but they aren't very comfortable. The earpieces can be wired in series to increase the impedance further but take care to get the phasing right. I made the mistake of "potting" the LT44 with silicon sealer in a small film canister in the headphone lead but the silicon compound affected the wires causing them to fail after a while.
Alan.