Once you take the plunge and get balanced cable for Pono, you must be deaf not to hear Huge improvement in sound quality. Compared to the “real world” outside of our heads and headphones, the improvement is comparable to bi-amping or setting the speakers into active mode. According to Pono info flyers, this is exactly what is happening. One of two headphone amplifiers is turned off when Pono is in a single-ended mode. Once Pono is set for the balanced mode, both internal amplifiers are used, one for each channel.
Balanced cable for HD-600 also fits Sennheiser HD-25 on-ear headphones, my saviors during long flights. I noticed that Pono sounds more open and relaxed with HD-25 than with hi-end HD-600. Is it lower headphones impedance, 70 Ohm vs. 300 Ohm? Who knows, all I knew is that there IS the difference and that I can hear the difference! Quick chat with Pono community pushed me toward Beyerdynamics DT770 Pro 80 Ohm cans. Am I glad that, for once, I listened! Below is a step-by-step procedure on how to rewire DT770 for the balanced mode. Original Beyerdynamics cord is discarded, I used generic Sennheiser cord instead, but Mogami wire may be used for those who do not have extra Sennheiser cords:
desolder original cord
using brute force and small chisel or needle separate decorative collar from the cord
add a strip of damping material to the earcups
insert and solder new wires
solder two 3.5mm connectors
Done!