Thank goodness, a non-volatile post. :-)
> Does anyone have some design to home brew a multiple headphone ummm
> Mixer? Ya know plug into a headphone jack and be able to have multiple
> headphones plugged in.
I have a distribution system in my rooms. I use the speaker outputs of
radios into a backwards connected 1-2 watt transistor output transformer,
like one of these from Mouser:
42TU120-RC 42TU048-RC
Almost any transistors-to-voice coil transformer will work.
The low-Z secondary goes to radios, and the ~40 ohm primary goes to the line
that headsets bridge across. I load the line with 100 ohms or so, to swamp
out load changes.
Unless someone has a really low impedance headset, like 16 ohms or less, or
the headset has really non-standard sensitivity, it works great.
http://www.w8ji.com/images/New%20Contest%20Room/NEW%20shack%20web/run-position-best.jpg
http://www.w8ji.com/images/New%20Contest%20Room/NEW%20shack%20web/all-ops.jpg
The little metal boxes have two SP12T switches for selecting any audio line
for each ear independently. None of the audio lines have a ground path,
except of course on the radio side of the transformers. This is important!!!
While rated at less than 1 watt, these transformers do not saturate or clip
well over 1 watt for almost all load impedances, so there is lots of volume.
To drive a speaker, I use a MFJ-616 bridged into a pair of switches than can
sum up to two channels, with a fader control between those channels.
This lets any operator listen to any radio in any ear he wants. I had
provisions for variable L pads, but found it unnecessary.
73 Tom
_______________________________________________
CQ-Contest mailing list
CQ-Contest@contesting.com
http://lists.contesting.com/mailman/listinfo/cq-contest
|
