Hi Charles,
Thanks for your insight into the Yamamoto. I would see if I can get my hands on one. It really could be an interesting upgrade from the NAD M51, that I love. Also, I need to check on the synergy of the components. My preamp and amp are truly soft, classic, flowing, organic SET sounding and that is why I tried with the NAD M51 Solid state DAC. For example, before I has this DHT preamp, I had a Hybrid (tube/SS) Sonic Frontier preamp. In that rig, I used to have a passive device between DAC output and preamp input. It was a box made of 2 old 111C Western Electric Transformers with RCA inputs and outputs. THis passive device cures any "digitalitis" in signals making the sound rounder and with less edges. Problem appeared when I added the DHT preamp, then I needed no more the passive device. On my next trip to USA, probably August, I will try to listen to the Yamamoto DAC!!