I've been playing around with some new gear and made some test recordings with an Oade T+modded UA-5 running coax into a Marantz PMD 661. The Marantz is really particular about accepting a digital signal. You have to set bit-depth and sample rate in the preferences menu before recording, and the source has to match those settings.
For the first test, I set the 661 to record at 24/44.1. I set the UA-5 output accordingly and made a short test recording. After hitting stop on the 661, but while the UA-5 and 661 were still powered up, I switched the UA-5's sample rate knob to 48 and tried to record the next clip. The 661 recorded just fine, but the file was still 24/44.1. The UA-5 has to be powered down before changes in output will be effective. After powering down and changing the UA-5 output to 24/48, I tried to record but the 661, still set to 24/44.1, would not. This was a consistent result in all the permutations I tried, and all test files were checked for bit-depth and sample rate in Wave Editor.
The other curious thing happened by accident. The 661 had been previously set to record at 16/48. I forgot, and set the UA-5 to output 24/48. The 661 took the signal, and the resulting file was indeed a 16/48 file. I don't know why the 661 will accept a 24/48 input signal while the preferences are set to 16/48 when it won't accept mis-matched signals in my other tests. Is the UA-5 output 24-bit, 16-bit, or both at the same time? Or is this something unique to the 661? Is there another test I should try? I am aware of the previous discussions about UA-5 output so these results were a surprise.