I recently purchased a 4 pack of Fancasee 3.5mm TRRS solder on plugs from Amazon to convert a couple of cables for use with the Digirig USB soundcard radio interface.
After I soldered up the cable to the connector and tried it out, I noticed transmit audio was coming thru the radio's speaker.
Switched back to the Digirig factory cable and it went away???
The micrometer and a visit to Digikey to get the specs on a known good part showed a .050" difference in overall length - the cheap plug was too long allowing the TIP to touch R1 inside the jack.
This, in turn shorts transmit and receive audio together.
Hope this helps someone else.
A $4 quality part beats a $2 cheapie most days...
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73
Mike N0QBH
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N0QBH Mike Berg