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Author Topic: HAMMARLUND HQ-129X HEADPHONES  (Read 617 times)
AC0FA
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Posts: 298




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« on: July 19, 2007, 10:48:56 AM »

I am concerned that hooking up the wrong set of headphones to a tube rig could be a shocking experience and result in poor performance.  

What are the most appropriate headphones to use with the hammarlund HQ-129x.

This reciever was built between 1947 and 1953.
I would expect headphones from 1947-1953 would be the most suitable and work the best.

Would something like TRIMM PROFESSIONAL 600 OHM work well?

 
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K7UNZ
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Posts: 691




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« Reply #1 on: July 19, 2007, 01:03:37 PM »

Made to work best with high impedance (2K+ ohm) as that's what was around at the time.  However, should work just fine with your Trimm cans.  Maybe a little louder than normal, but that's not always bad in a vintage receiver.....hi!

Enjoy the radio and remember, once upon a time it was state of the art.....

73, Jim/k7unz
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KA5N
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Posts: 4380




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« Reply #2 on: July 19, 2007, 01:09:54 PM »

According to the manual and the schematic, the phone jack is connected to the 6 Ohm winding of the output transformer.  So it should work fine with just about any impedance phones high or low.  Back in the 1950's the most common headphones used were WWII military surplus phones.  Mine cost $1 and were indestructable but were "tinny" sounding (maybe because the diaphram was made of a flat piece of steel that looked like the lid off of a tin can).  Trimms should do just fine.
Allen
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KE3WD
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« Reply #3 on: July 19, 2007, 06:40:50 PM »

AND-- the output transformer winding is isolated from voltages.  

Standard 8ohm phones up to about 22 or so will work fine.  

Dynamic type will sound better IMO.  


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KE3WD
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« Reply #4 on: July 19, 2007, 10:36:12 PM »

>>>Would something like TRIMM PROFESSIONAL 600 OHM work well? <<<


Likely way too high impedence to hang onto a 6 ohm audio transformer secondary.  

Would work, but volume may be decreased.  

Ohm's law.

Full Range "audiophile" cans aren't of much use on HF bands, they will just make the noise more intolerable.  

Dynamic 8 - ~32 ohm voicecoil headset, older vintage design, will likely work and sound the best here.  You may be able to push the impedence up to the 100 ohm mark.  It is getting hard to find 8 ohm cans these days, although the thrift shops and such cough 'em up on the cheap quite a lot.  

Remember also, most all you will find today will be stereo.  You will have to consider that when selecting impedence because you will either have to get a stereo to mono adaptor or wire on your own mono plug at the end, combining both sides in parallel, which will half the impedence.  So a 32 ohm headset wired in parallel would be a 16 ohm load to the radio, that wouldn't be a bad tradeoff.  

RodeoShark Model: ACM-500RB  |  Catalog #: 55010865

is 10 bucks.  

More than adequate for listening to an old Hammarlund.  



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