What amazed me was they designed the boards to accept the upgraded transformers. The original ones were about $20.00 and the upgraded ones were $31.00 + shipping.
It was very professional for PS Audio to give the information for the upgrade. I could not have figured it out on my own. The price to performance must have been to low for them to use the higher grade transformer or there were other considerations that gave it better sound. The DAC got rave reviews when it was released.