Balanced Digital (SPDIF) cable

I made a simple SPDIF cable using Category-5 cable, and I feel great improvement over an optical fiber or a coax SPDIF cable. It is a modification of Zuka’s cable driver. The input jack, which plugs into the digital-output device like CD player, is directly connected to the cable driver part. One CMOS inverter is used for threshold, then the signal is converted to balanced output by LTC1485. 　I designed that the power can be supplied from the local transformer, or from the DA converter side via unused pair of Category-5 cable. It is possible to share same power supply with receiver, but I am not sure it is good for the sound or not, and I use a transformer at the input side to power the cable driver.

I also implement a receiver. The first version uses just a pulse transformer at the receiver side. It worked, but the sound quality was far from what I expected. Even an optical cable sounds better than the first setup. Thus I put a 110R termination register. There is some improvement over the first version and sounds better than the optical fiber, but it is still not as good as very short coax SPDIF cable. I decided to get rid of the pulse transformer and use a differential receiver, just as seen in the datasheet of LTC1485.
The key improvement might be achieved by known-impedance cable and proper termination. Although the cable is outdated (category 5 is not commonly used now, and 5e or 6 are popular for 1G network), it works great.