RE: Yggy v. Ayre Codex
They sounded exactly the same to me and another guy who owns Senneheiser 800 headphones. We tested them on my system:
Magnepan 3.7i speakers, Sanders Magtech amp, Audio Research Ref5SE preamp, Shunyata Zitron Python XLR interconnects between the DAC and preamp, Sonore Microrendu with Uptone LPS-1, Curious USB cable/Oyaide USB.
When we first tested them, the Codex seemed to have more liquid mids, but the Yggy seemed to have better bass. Then we realized that they weren't volume-matched. They were only about a 1-1.5db difference. We also didn't use the same interconnects. After we volume-matched, we could not distinguish the two.
The Yggy with Curious cable also sounded the same as through my Singxer SU-1 with Transparent Reference AES cable. However, the Oyaide Neo d+ cable didn't sound as good as the Transparent/Curious on the Yggy.
YMMV