I was greatly relieved to find the Onkyo RDV-1 does indeed accept 96kHz inputs (in either coax or toslink, it turns out). I run all my digital processors at 96kHz. When I first opened the box I checked the manual, it said it only accepted up to 48kHz. Despite my lack of time on Saturday, I quickly hooked up my new Black Lion Micro Sparrow ADC (mk1) to the Onkyo, and found it handled 96kHz fine and even shows a message saying it is doing 96kHz. The Onkyo does not accept digital inputs higher than 96kHz, when given such inputs it displays the LCD rate, either 44.1 or 48khz. I did not listen to see what those did. But 96kHz in several tests over the weekend appears to be rock solid and sounds fine through the "stereo" outputs (not the same as the "front" outputs on this player…the "front" outputs sound very thin as subwoofer use is assumed--UPDATE, this may not be true with digital input--all were measured to be flat). I measured the Stereo outputs with pink noise (which is random, so always fluctuating and never perfectly flat) and it looked as good as it gets with random noise measurements:
I've been pouring over the service manual schematic to see what the circuitry is like. The output board has each output channel going through a 4580 opamp, then a 47uF capacitor, a small resistor, a number of shunt muting devices, and then the output. Not wonderful but not too bad either. I'd like to replace that electrolytic cap with a Teflon. But what is a 4580 opamp?
Apparently it's similar to 5532, a higher current bipolar amp. The 4580 is said to be much better than the 4558's used ubiquitously in "mid fi" audio equipment, maybe even some not so mid fi.
While researching this, I found the quotation from John Curl himself, as of 2009 his CD player uses 4558's (!!!)