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Old September 18th 06, 03:51 AM posted to rec.radio.amateur.boatanchors
Smokey Smokey is offline
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First recorded activity by RadioBanter: Sep 2006
Posts: 17
Default Wanted:4 or 8 ohm to 500 ohm xformers

Scott, Mike, Michael and Ed... Thanks so much for all the G R E A T
suggestions!! I really appreciate you guys taking the time to help me out.
I've consolidated my 5 boatanchor receivers into a station control that
selects an 'ol R-42 speaker in the shack (500, 600 or 5000 ohms) and a more
modern 4 ohmer outside the shack in the workshop and with a toggle I can
listen while I am a-whittlin;----well I have noticed that the menagerie of
output impedances makes the R-42 BOOM IN while listing on an SX-42 but
switch to my SX-146 and it just doesn't have the same horsepower. The
reverse is true on in the workshop on the modernly 4 ohm speaker. So I
decided the easiest thing to do is hitch up some sort of impedance
transformer and bring all the receivers into commonality . THANKS
FELLERS---you made my day.

73 Smokey

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"Scott Dorsey" wrote in message
...
Ed Engelken wrote:
An ordinary filament transformer with a 120 volt primary and 12.6 volt
secondary will work well. The turns ratio is about 10 to 1 and that
yields an impedance ratio of 100 to 1. That will match a 600-ohm
output to a 6-ohm load and will provide a decent match to an 8-ohm or
4-ohm speaker. A small 1 amp. transformer is sufficient. --Ed


Note that the frequency response may be deficient... then again, it might
also be great. Those Western Electric wall warts that were used for
princess phones used to be flat from 50C-10KC easily and I saw more than
one broadcast station that used them as improvised audio transformers. On
the other hand if you buy a modern Talema toroid from Digi-Key you'll find
the response drops off dramatically above 100C or so... which is great for
keeping power line trash out of power supplies but not so good for audio.

If you don't know, run a 1 KC square wave through it with the loading you
intend to use and watch the output on a scope. The calibration output on
a Tek scope is just fine for the application.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."