help: managed to screw up a diy cable
May 3, 2015 at 11:31 PM Thread Starter Post #1 of 2

gcb0

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i just soldered a shorter cable for my mini-xlr cans... and the cable is all screwed up and i have no idea how to "debug" it. so i appreciate all info you are willing to share before i repeat the same mistake with my last mini xlr connector.

first thing, i probed with a multimeter the original cable. pin 1 is ground (TRS base) pin 2 is channel 2 (TRS middle) and pin 3 is channel 1 (tip of the 3.5mm TRS)

i got a ttrs cable and removed one end. soldered the base to pin 1, tip and adjacent middle section to their respective channel pins and left the other middle section (closer to ground) unconnected.

the multimeter continuity test says there's no short. i completely forgot to test that cable before btw.

but as soon as i connect my cans and my phone i hear static... well it's not like static.... it's "something" but very faint. when i play anything it will just mute and do random low volume isolated pops.

i have no idea how to debug it... i may have screwed up on the ttrs to trs concept... was it right to just leave the rear middle section unconnected? (note i will only use the can with ttrs female jacks anyway)..

some random multimeter probes. resistance with the good 3m cable is 0.6ohm all around. with the short bad cable it's 1ohm.

i tried hooking the multimeter to xlr pin 1 and 3 and measuring ac voltage while the ttrs end was plugged into the phone playing music... don't even know if i will see anything without load, but... with good cable i see it oscillating from 1mv to 5mv. with the bad cable is around 100mv...
 
May 3, 2015 at 11:58 PM Post #2 of 2

gcb0

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apparently in the years i wasn't looking, m$#%&@$ f@&#&# apple stated making TRRS plugs with ground and mic inverted just so people couldn't use the headsets on Nokias...

and that is now the "standard"

sigh... testing the cable with a 6.35 TRS sleeve on the amp worked perfectly. only if i hadn't to use the cable on plugs that do expect the mic pin...

well, one more lesson in the course of "read before solder" class.

if anyone want a garbage short cable to connect 3.5mm TRS to mini-xlr just let me know. it's 1.2m.
 

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