Just to kill the curiosity, I hooked up ASUS Xonar Essence One to my QLS QA-660.
Seemed the process didn’t click that easy. Xonar Essence One failed to capture the S/PDIF signal above 44.1 kHz sent by QLS QA-660. I thought I have a bad Coaxial cable, but eventually the Optical got same issue. USB seemed fine though. I could easily got a bit-perfect output by using WaveLab in ASIO mode. Playing up to 192 kHz material was so smooth and hassle free.
Then, I upgraded the QLS QA-660 firmware to the latest one V1.2. It didn’t much help. Still all materials above 44.1 kHz failed to be recognized by Essence One.
Another tried was to upgrade the ASUS Xonar Essence One MCU firmware to 1.27. The problem was: I failed to upgrade by using my laptop (Essence One was not detected by the upgrade program). I moved to another laptop then the process could be done smoothly. Could be one of my laptop got some USB driver issue.
The problem seemed solved. Xonar Essence One now able to recognize any signal above 44.1 kHz, except 192 kHz. So I have limit up to 176.4 kHz. Quite a strange issue. When I played 192 kHz material, Essence One seemed failed to recognize it. I think I have to wait for another round of firmware update then, either from QLS or from ASUS. I didn’t think I have a bad Coaxial cable…
Overall the sound of ASUS Xonar Essence One was impressive. Tonal balance seemed quite neutral. Bass was well pronounced, tight, with enough slam. High and mid-hi were slightly on the bright area. Detail and speed were impressive. Vocal was good, not too thick or warm though. Hey, this was sort of LM4562 sound! (LM4562 was used on this machine as output buffer stage and I just realized when taking detail photo of this machine). Would see if changing some opamp could impact the sound significantly (not mentioning some potential upgrade in the power supply section).