[R-390] 600 ohm audio

[Tom Frobase]

This is totally off subject; for the last 10 years I have been using a
Lectrosonics AM16/12 mixer. This particular family of mixers has long been
discontinued, but still show up on eBay at a very reasonable price.  The
mixing interface is a Windows XP gui which is attached to the mixer via an
RS-232 connection.  In my case I run a virtual XP machine in my station
computer for configuration.  All things audio in my shack end up in the
mixer.  The mixer input impedance is 600 ohms, I pad radio speaker outputs,
military radios drive the input directly.

Here is the cool thing, once the software is set up it does not have to be
accessed via the XP window, settings are stored in the mixer, the mixer is
designed so that loudest wins.  So once configured the loudest radio volume
control takes control.  I run the output through a small Lectrosonics 8
channel amplifier.  The whole set up cost less than $100, the AM 16/12 was
new in the box.  I see the current version DM 812 is selling for $100.  I
have 6 radios working through the mixer.  I also pass my SDR computer
output through the mixer as well.  Attached is a picture of the mixer and
amplifier.  The note on the mixer is my cheat sheet for my HP 3488 antenna
relay switch, but that is another story. ... tom, N3LLL

On Tue, Feb 22, 2022 at 6:30 PM Roy Morgan <k1lky68 at gmail.com> wrote:

> Late to comment also:
>
> The original poster showed a photograph that he ALREADY HAS A VERY FINE
> line to voice coil transformer.
>
> Attached is the data sheet from a 10-watt line transformer. The 10-watt
> line input tap is rated at 500 ohms impedance - this is ideal for the
> R-390A line output to drive a normal speaker.
>
> Some notes:
> -Stated impedance of speakers VARY GREATLY over the range of audio
> frequencies
> -The R-390's radio maximum audio output available power is about ONE WATT
> (?)
> -A reasonably efficient speaker gives you plenty of sound driven by a
> small portion of a watt.
> -Most any line to speaker transformer will "work a treat", even though
> original costs and quality levels varied greatly**
> -Some such transformers are meant for 25 volt lines. Input impedance for
> them at corresponding power levels will be lower.
>
> **My security contractor suggests that I neither confirm nor deny that I
> have a pair of Altec Lansing Peerless Type 15066 line transformers rated at
> 8, 16 and 32 watts operating level.
>
>
>
>
> Roy Morgan
> K1LKY Western Mass
> K1LKY68 at gmail.com
>
> > On Feb 19, 2022, at 10:33 AM, Tisha Hayes <tisha.hayes at gmail.com> wrote:
> >
> > (Sigh) late to the conversation but I have a few things to add;
> >
> > If you are going to browse through ebay for 600 ohm to 8 ohm transformers
> > they can be a little pricey.
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