I think the UA5 *needs* to be run at 24/96. The A/D sounds VERY different in 24/96 mode than either 24/48 or 16/44.1. It really opens up the sound, cleans up the highs, it's the proverbial veil lifting.
I don't think this has ONLY to do with wordlength and sample rate. I have been reading a buttload of info about ADCs and DACs lately, as I was shopping for a home hifi DAC, and I learned alot about how digital chips work.
For instance, and I'm going to take you on a bit of a tangent here, so bear with me... I run a Cary CD308 as a CD transport to feed my DAC. When my DAC locks onto a signal from the Cary, I see a lock at 17/44.1. Yes, that's 17 bits. WHAT?? But when reading through an article on the Perpetual technology duo, I may have stumbled upon something that explains why the Delius is locking to the Cary (in non-upsampling mode) at 17/44.1..
http://www.soundstage.com/revequip/perpetual_p1a_p3a.htmIn particular, the following:
"Peter Madnick clarifies the operation of the P-3A and other so-called 24/96 DACs and 24/96 outboard processors this way: The P-3A does not interpolate 16-20-bit data to 24-bit data -- nor does any 24/96 DAC (e.g., the Bel Canto DAC1) or add-on 24/96 external device (e.g., Assemblage D2D-1). All of these products, so far, will output 24-bit data via dithering of the 16-bit input data. This results in data that has roughly 17 bits of equivalent resolution within a 24-bit datastream."That *has* to apply here. So the Cary is reading the data off the CD, inputting it into some digital chipset, and dithering the 16 bit data. Then, if you don't have upsampling on, the digital coax out spits out the resulting 17/44.1 signal, or if you use the internal DAC it would sent it to the burr-brown 1704 (which is a 24/96 DAC, makes sense it would want to see 24 bits coming in). This means it's spitting out a signal to the dCS that is dithered, but not yet padded with 0's to 24 bits.
UNLESS you turn the upsampling on, which not only spits out 24 bits to the dCS, but also 96khz. So in the scenario above, after the 17 bit data is sent along it's merry way to Cary's custom DSP engine, it interpolates to 24 bits, and then runs upsampling to 96khz. So the Delius sees 24/96. From the article:
"The P-3A and other 24/96 products do upsample, for example, from 44.1kHz to 96kHz if you select that mode. People tend to assume that 24/96 products that advertise upsampling and/or interpolation actually convert 16/44.1 data to full 24/96 resolution, which is not accurate. To actually get 24-bit data in a 24-bit datastream, you must use digital signal processing (DSP), which is included in the P-1A and is referred to as "Resolution Enhancement" in the P-1A's user manual."OK, so what I'm getting at here is the DAC in the Cary needs to see 24 bits to do it's DACly duties. The data is well on it's way to dithering (interpolating) to 24 bits even before it hits the digital coax out.
To come back to the UA5 discussion, that ADC obviously is a 24/96 device (anyone know which one??), and it really wants to operate at 24/96. Anything you choose below that is not running a separate DAC, but dithering/downsampling to whatever you choose. And I surmise that the dithering/downsampling algorithms aren't that great.
SO what I'm saying is, I don't really like the UA5 as an ADC until you run 24/96. But at 24/96, it's MINDBLOWING.