There's quite a few, off the shelf, 7 or 9 pin SIP devices that are
basically for automotive radio outputs, being 2 inputs and 2 low Z outputs
that operate directly from 12 to 15 volts DC. External required components
are usually 3 to 5 pieces for decoupling and feedback/gain control. Cost is
in the $5 range or less.
Or Radio Shack has some small amps for that purpose that are in the $20
price range.
73
Bob, K4TAX
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
To: <tentec@contesting.com>
Sent: Wednesday, January 16, 2008 10:25 AM
Subject: Re: [TenTec] Heil headphones
On Wed, 2008-01-16 at 04:42 -0800, Dennis OConnor wrote:
So far I have not seen anyone offer a circuit for an audio breakout box
which will have an audio amp(s), volume control(s), and jacks for 2 or
more headsets with their microphone circuits... This would be really
handy for lots of rigs, and for visitors to the shack to be able to don a
headset and listen or operate also.. Also, very handy for a teaching
situation where new ops are being introduced to contesting... I have idly
made a beginning on this circuitry in my head, but being truly lazy I am
waiting for someone else to offer a debugged and working circuit for me
to build..
denny / k8do
Start with a convenient audio output IC, maybe a vintage LM380 or LM384.
Add the controls to the input of the schematic on the data sheet, add as
many jacks as desired and its done. Hardly worth drawing a picture,
nothing unique enough to need fancy artistry. Could be extracted from
any receiver project in most any recent ARRL Handbook. Such as figure
22.48 in the 2002 ARRL Handbook which has multiple inputs for one output
or 22.56 that has multiple outputs (mostly low level) from one input.
Or look for a computer speaker amplifier an add a forked output cable
with multiple headphone jacks. Off the shelf and probably ready to work
though some may not like having a transmitter near them.
73, Jerry, K0CQ
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