[R-390] 600 ohm audio

[Tisha Hayes]

(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; People who have them know that they are
sort-of-rare and charge accordingly. But... people who are selling off the
old 70 volt field coil transformers do not know the other uses for the
transformer as an impedance converter from 600 to 8 ohms; You can get those
pretty cheaply.

If you look at old speakers there were quite a few that were originally
designed for 600 ohm sources. Some of the Hallicrafters speakers supported
a 600 ohm input and if you took the speaker apart you would find a little
transformer in there.

You can also get transformers that are multi-tap and that allows you to
match up to 4 ohm speakers as well. Just checking quickly I see that
radiodaze has the 119DA that would allow you to connect up a 4 or 8 ohm
speaker just by using a different tap.

Another alternative would be to make your own little audio amplifier that
can take in a high-impedance input (600 ohms, whatever) and drive an output
to 4 or 8 ohms. You could even do it with an op-amp or a simple transistor
based amplifier because those devices don't really care about the input
impedance that much and are capable of driving low impedance outputs (just
not at a very high level), so it would be good for low impedance headphones
or ear-buds.

If you want, you can even find 600 ohm headphones, but nowadays those are
usually high-end studio headphones. I have the Sennheiser HD600 that I do
use for radio listening but mostly I use them for high fidelity music
listening. Those are pricey ($300 headphones) and might cost more than your
radio. Another place I have found impedance adapters are the ones used for
David-Clark aviation (pilots) headsets.

Another route I took was to get a Bogen distribution amplifier; This is a
monsterous, 50 watt audio amplifier that you would use for a building and
had a 600 ohm input that could drive a variety of output impedances. If I
ever have a south american dictator surrounded in an embassy and I want to
drive them crazy/ out of the embassy I would use that to play Barney the
Purple Dinosaur songs non-stop for a few weeks. (or anything from
Nickelback).

*Ms. Tisha Hayes*

*AA4HA*