On 1 Feb 2002, at 0:05, George, W5YR wrote:
> Steve, I suspect that lack of an external speaker jack comes with the
> type of audio output circuitry used in the Pegasus: balanced output to
> ground and no ground. A two-circuit connector would have to be used
> and virtually all external speakers have one side of their input
> grounded at the connector.
>
> An external speaker could be easily used if an isolation transformer
> were employed.
>
The Jupiter does have an external speaker jack even though it uses
the balanced output power amplifier like the Pegasus. The sleeve of
the external speaker jack is one side of the balanced circuit and the
tip is the other. Therefore, any low impedance speaker having a
standard 1/4 inch phone plug can be used UNLESS one side of the
speaker circuit is grounded in some way.
I have checked many of my speakers including ones from Ten Tec,
Drake, hallicrafters, Hammarlund, Mosley, Radio Shack, and a few
others and in every case, they are floating. So to use any of them
with the Jupiter all I need to do is attach a 1/4 phone plug and play.
In both the Pegasus and the Jupiter, the line output in unbalanced
and one side is ground. So it is easy to connect that to the input of
an external amp without use of an isolation transformer.
That said, I use a 600 ohm to 600 ohm 400 mw isolation transformer
for most audio connections here and have done so for most of the
last 30 some years. The transformers are small, inexpensive and
break any potential ground loops that may sneak in. I mount them on
a piece of perf board only slightly larger than the outline of the
transformer itself. That provides convenient and secure mounting of
the cable. I then cut my interconnecting cable somewhere near the
middle [not critical] and wire the transformer in place. Finally, I
cover the whole assembly with a piece of shrink tubing to insulate the
connections and protect the transformer. I call it a "bump in the
line" arrangement. You now have a transformer isolated connecting
cable.
I prefer to use the line output of the radio into my 6BQ5/EL84 amp
wherever I can as it almost always provides much better audio
quality than the internal audio amplifier, even when the radio is used
with an external speaker.
You just cannot beat those tube amps for a nice "warm" sound! :-)
OK..........pretty bad.........I know.
I'll leave,
-73-
-Lee-
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