[R-390] 600-ohm phones?

[DW Holtman]

Hello,

There are lots of new 600 ohm headsets out there for sale. Here in one 
example.

http://www.smarter.com/telex_instructional_610_41_binaural_ear_cup_600_ohm_headphone---pd--ch-2--pi-671077.html

Best,
DW Holtman
WB7SSN



2002tii wrote:
> Tim wrote:
>
>> What 600-ohm headphones are out there? I've got a number of older 
>> military radios that evidently were built to drive 600 ohm phones. 
>> Some sort-of drive 8-ohm modern phones but have some problems with 
>> level or matching or something.
>
> I am not aware of any commonly-available phones that have impedances 
> as low as 8 ohms.  Most are in the 200-350 ohm range.  Of course, if 
> you drive both channels of 200-350 ohm stereo phones in parallel, the 
> load would be 100-175 ohms.  The lowest impedance phones I know of 
> currently are some new Denon phones at 25 ohms (AH-D2000 and 
> AH-D5000).  Koss has (or had) some 60 ohm phones.
>
> A small filament transformer, say 20-24 volt secondary (for 120 volt 
> primary), with the radio hooked to the primary and the phones to the 
> secondary, works great.  That is more step-down than you need for 
> 200-400 ohm phones -- a 50 or even 75 volt secondary would be 
> sufficient, if you have a problem with low output from a 24 volt 
> secondary.  This works for speakers, too -- and it even tests way, way 
> better than your boatanchors sound.  Before I went exclusively to line 
> level outputs feeding a preamp, I used a homemade speaker with an 8 
> ohm driver and a 15 volt power transformer to listen to my 600 ohm 
> radios.
>
> For that matter, I have had good success using the two, 300 ohm 
> elements of my Sennheiser HD-650s in parallel (150 ohm load) directly 
> from the 600 ohm speaker output of boatanchors.  Not that most folks 
> would buy the 650s to listen to boatanchors, but I have them around....
>
> Best regards,
>
> Don
>
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