I tried comparing excellent disc transports with Mac mini/USB based system and found that disc transports are more consistent in sound quality, that is - consistently inferior to the Mac mini. Particularly the sound stage size and that annoying glare. The few times that transports are better, it is in the bass, pace and rhythm area. Rock music works quite well, for some reasons. May be the Mac mini is too clean and too low on jitter? May be jitter is a good thing for rock music? hmmm....
The Genesis Digital Lens, a unique piece of audio equipment. There are (were) other similar products such as the Theta TLC, Monarchy DIP, Audio Alchemy DTI Pro, Sonic Frontiers Ultra Jitterbugs, Meridian 518s and Apogee Big Ben. But these use phase-locked-loop to reduce jitter, which is pretty common feature in most of today's DAC anyway. Modern re-clocking units like Empirical Audio's Pace Car and Firestone Audio's Bravo focuses on de-jittering the USB data stream. The Bravo also accepts S/PDIF coaxial and Toslink, but just synchronizes data to its clock with no memory buffer, so it will be much less effective as jitters are errors in time domain and you can't give it new rhythm without stopping it first.
The Digital Lens uses a theoretically superior method which is a data buffer that holds the bits in its memory, re-clocks them, and then outputs a jitter-free digital stream (well..jitter in the stream removed, but the Lens' close-to-zero clock jitter remains). Some disc transports do this (such as Theta Jade, Esoteric's higher end models), but it is quite rare. Since the Digital Lens was actually part-designed by Paul McGowan of PS Audio (he co-founded Genesis Technologies and co-designed the Lens), new PS Audio Perfectwave Transport do this too, but there are no stand alone product like it that I know of.
The Lens is house in black aluminum face plate, high-quality input and output jacks. The unit has 5 digital inputs (RCA, BNC, Toslink, AES, and Glass optical) and 3 digital outputs (RCA, AES and Glass). Input is 16-bit only. Other than buffering and re-clocking, it can also add bits from 16 to 20-bit, and with two type of dithering. Dither 1 uses more advance triangular dithering and is considered superior. The remote control lets you set the Lens' dither mode and 16/20 bits from your listening position. The Lens also measure the speed accuracy (in parts per million, "ppm") of the transport's clock to which it's connected. My 47 Labs' Shigaraki transport measures at 18ppm positive while the Teac VRDS50 measures at 20ppm. Ironically the cheaper Sony CDP-X5000 measures only 14ppm. Genesis says anything from 10-50 is of ok quality.
The sound from the memory buffered Digital Lens should be, in theory, identical from transport to transport, but it does not. Let's just say it makes any CD transports sound more open with better definition. There are less harshness which are common in older CDs. The sound quality in general is as good as the Mac mini (via Halide bridge asynchronous USB/SPDIF converter feeding the DAC.)
Stereophile 1996 review of the Digital Lens can be found here.
Having spent most of my time lately using computer-as-source, the benefit of having instant access to your full music library is something I am now so addicted to. Reaching out for that CD, once seems like a ritual, now feel like labor. It will be interesting to see how the Lens will fix jitter-prone output of an Apple Airport Express, and would it transform the sound quality to high-end levels. I do really hope that PS Audio or someone will come out with a modern version of the Digital Lens with ultra accurate clock, 24/192kHz capable inputs, dithered digital volume control, asynchronous USB capability, and buffered digital output (see Lampizator Transport). That would be a product to rule them all, wouldn't it?