OR4 was in a shootout with EVO 2 years ago at RMAF.
Take a look at this thread: http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/best-usb-spdif-converter-12904/index3.html
It's long, but worthwhile I think. Several posters heard several units side-by-side. Particularly, bhobba thinks the OR5 is best, while Elberoth believes the Audiophilleo with Pure Power is best, second by M2Tech full Evo stack and OR5. BTW look at Elberoth signature to understand his reference point: DCS Scarlatti.
A very knowledgeable poster on yet another forum mentioned these differences might be due to S/PDIF compatibility (or synergy) between the DAC being used and the converter. Maybe it is best to find other users with your same DAC and asked them what converter they use and why. Just a thought.
Myself, I will be buying an Audiophilleo 2 to pair with my Metrum Octave, and maybe later add the Pure Power option.
Happy new year!
I have the Audio Note DAC 3.1 SE kit arriving next week, and are to hook it up to an EVO plus clock plus outboard power supply built by Cables R Us UK. I used to have an Audio Note DAC 1.1 kit. with a CEC TL51 CDP. I am jumping into PC audio with a Mac Mini (I use Macs day in day out as am a web designer).
I am hoping the Mac Mini plus EVO stack will equal or better my CEC CDP. It should in theory I think. I was to use Pure Power software, and stuff 8 gig ram in the Mac Mini.
I use Audio Note AN-V RCA Coax for the EVO to DAC, and Audio Note RCA AN-V for DAC to pre amp. I use a factory Audio Note M3 pre and a factory Audio Note Conquest monoblock pair with 2 x 300b tubes and 1 x 6SN7 each channel.
I note the DAC 3.1 uses 2 x 5687s on the output board, which my M3 does as well, also the same is a 6X5 for the rectifier (which I swop out for a Bendix 5852 as it has more power draw and better bass).
I am a bit nervous doing all these mods to my system in one go. I was happy with the DAC 1.1 sound, though it was a tad forward though very organic and smooth, with no treble edge. It's only failing if it had one was it was a bit hissy and hum levels were a tad high. It couldn't be beat at it's price though, and was close to vinyl.
I am not sure why more folk don't look at the Audio Note Dac kits (or UK factory products) as they are superb DACs. The nearest I have heard to analogue and can listen for hours with no fatigue.
They major on NONE OVERSAMPLING AND NO FILTERING.
The parts quality is also top notch (BlackGates, Elna Cerafines, Tantalum Resistors, Silver wiring, Top quality design, IV Transformers between the digital and analogue sections (most important) and Transformer Coupled Output.