I finished my DT880-600 balanced mod today!
Sugru does work really well plugging the existing holes in the cups:
One word of caution if you’re gonna try this…I did make one mistake that ended up not being a problem because of the highly symmetirc design Beyer put into these. See if you can spot it:
If you noticed the red electrical tape - which I’m using to mark the right channel - is covering the plugged stock cable hole, YOU WIN! I wasn’t paying close enough attention and drilled the new jack hole on the wrong side of that stock cable opening as viewed front to back. Oops. But, because of the new dual entry and pretty much everything being symmetric, the fix was easy. Just make what was the left cup the right cup. I even was able to flip the headband around so that the “R” on the head band is on the same side as that red piece of electrical tape.
So far so good. Everything works. Both SE and balanced cables I have on hand are playing fine.