Yes the mono to stereo adapter does just short the mono signal to both stereo signals but that is not the problem.? The problem is when you insert a mono plug into the uBITX stereo jack it shorts the ring connection (and the output of U1) to ground.? If the ring connection is left open there will be no short when a mono plug is inserted.
I assume the mono to serial adapter would just short the mono signal to both stereo signals. So you are back where you started, plugging a mono jack into that adapter will kill the TDA2822M. Could work if you avoid this, but not foolproof.? And thus not suitable if I'm anywhere in the vicinity.
Might be better to add a series resistor inside the radio, and/or reduce the supply voltage to the TDA2822M
Jerry, KE7ER
On Wed, Feb 28, 2018 at 09:22 am, K5ESS wrote:
It appears at least a few folks have fried U1 by inserting a mono plug in the speaker jack and shorting out the audio.? I¡¯d recommend only wiring up the tip connection and not the ring and then using an external mono to serial adapter for your stereo phones.
