[R-390] 500/600 ohm audio to 4/8 ohm speakers

[Chris Kepus]

Hey Walt,

Thanks for the great info and going to the effort to share it!!.  There's a
lot of folks who enjoy monitoring this list for the chance to learn
something new and specifically to learn how to keep our R-390A, or whatever,
playing sweetly. 

As you pointed out, and was expanded by Tom, there are many ways to arrive
at a solution and many reasons for choosing a path that is a bit more
challenging and fun (here's a great "general" example by Tom: "
....reinventing ways to use electronic components and other things around
the shack and shop..".  
I'm another one that constantly reads the QST's, CQ's, and 73's from the
40's and forward.  Amazing what was and can be accomplished with
imagination, experimentation, and creativity. 

Merry Christmas to all!!
73'
Chris
W7JPG 


-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of KR4HV
Sent: Tuesday, December 25, 2012 5:54 PM
To: R-390 at mailman.qth.net
Subject: Re: [R-390] 500/600 ohm audio to 4/8 ohm speakers

I have posted the spreadsheet file at https://www.box.com/kr4hv filename is
"Public address line transformers for speakers", but "box" is having some
issues just now.  They are working on it. Try to download it later, maybe
tomorrow.

I hope this link works out when "box" gets it fixed.  It's my first try with
Box.com  Someone let me know when it works.

I should say here that I have no transformer preference or brand to promote.
The two I listed on the spreadsheet were picked at random and just came up
when I was looking myself and I bought one of each.  They work fine
business. They are just common PA transformers with the Quam probably being
a little higher quality buy I haven't yet proven that to be true.
I also have some military surplus ones but they cost more and the freq.
response is not good and is stated as 300-400 cps to 3000cps vs. so on a
couple of them.
Of course there are also Hi-Fi ones available for even more dollars.

The older, experienced members here won't need the spreadsheet at all but it
may help some of the newer Hams, SWLs and BA owners out.
The intent was more to show the voltage-impedance relationship and explain
the additional uses for those that might not be as proficient and
experienced as others and to identify a common available industry group of
fairly easily obtainable transformers that will give more than acceptable
service for communications receivers. Nothing more, nothing less.  The
public address transformers available range from passable to good to
excellent and there are exceptions to all. I don't have a preferred
manufacturer and part #. Review the manufactures specifications vs. cost
make your choice.  

This is one of my first posts. I certainly didn't mean to open a can of
worms, or in this case, transformers.. LOL.

Regards and Merry Christmas to all.

Walt
KR4HV

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