Does anyone have any audio impedance matching transformers and is willing to
sell them? Specifically I need four 4-ohm to 500- (or 600-ohm and one 8-ohm
to 500- (or 600-) ohm. Please state price. If you have five with either a 4
or 8 ohm primary, that will do too...my need is not critical. Thanks!

Smokey


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Smokey wrote:
Does anyone have any audio impedance matching transformers and is willing to
sell them? Specifically I need four 4-ohm to 500- (or 600-ohm and one 8-ohm
to 500- (or 600-) ohm. Please state price. If you have five with either a 4
or 8 ohm primary, that will do too...my need is not critical. Thanks!

My suggestion: get speaker transformers for 70V distributed PA systems and
run them in reverse. Your local installed sound place will probably give
you a bunch of scrapped ones for free.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On 17 Sep 2006 14:13:31 -0400, Scott Dorsey wrote in :
Smokey wrote:
Does anyone have any audio impedance matching transformers and is willing to
sell them? Specifically I need four 4-ohm to 500- (or 600-ohm and one 8-ohm
to 500- (or 600-) ohm. Please state price. If you have five with either a 4
or 8 ohm primary, that will do too...my need is not critical. Thanks!

My suggestion: get speaker transformers for 70V distributed PA systems and
run them in reverse. Your local installed sound place will probably give
you a bunch of scrapped ones for free.

And if not, then they're not at all expensive new, whether from Radio
Shack or a full-service electronics shop. They tend to be 600 Ohms to
16/8/4 (and a slew more) Ohms. If you're in the UK, Maplins may have
them, or one of your mail order houses. Here in the US, I get mine
from Radio Shack locally, though Mouser, Allied, and Jameco also carry
them via mail order, and Cinergy (formerly Radio Supply) in Oklahoma
City sells them, too.

--
Optimist: There is a light at the end of the tunnel.
Pessimist: ... it is an oncoming train.
Cynic: ... and it is late.

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

"Ed Engelken" ) writes:
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

And in the days of when boatanchors roamed the earth, one guy suggested
in a magazine article that this was a good way to use up all thos
400Hz transformers that most ended up with a stock of via surplus,
but which weren't too useful for power applications, since few
had a source of 400Hz power.

I guess the trick today is to find a piece of consumer electronics
in the garbage (so long as it doesn't use a switching supply) and
use the power transformer from that. Filament transformers are
as likely hard to come by as audio transformers these days. (Not
that either is really that hard to get, but if one doesn't have a
handy audio output transformer, they are likely to not have any
filament transformers handy.)

Michael

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."

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

--
Important note: When replying to my e-mail please delete the words, "nospam"
from my e-mail address.
"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."