Hard to beat the $/perf. ratio of Musical Fidelity's V-link, reviewed back in Spring 2011:
That said, I have noticed that some e-tailers are now charging up to $40 more than the earlier $170 -- inflation?
IAC, the V-link is a bit cumbersome and not very portable -- that's important to me, anyway. It did measure well, but as noted by JA, is limited to 96kHz.
Low-/mid-$ competition is a GOOD thing! And the "industry" finally seems to be getting the message that (relatively) low-$, asynchronous mode + high-rez (24-bit/192khz) USB-SPDIF (or USB to I2S) converters (whether sand alone, or DIY kits, or engineered "OEM" solns for developers (see below) is a important (= makes a worthwhile sonic diff.) and marketable.
Some lesser-known manuf's (and related product offerings) are below:
>> UK-based XMOS has a decent model called “USB Audio 2.0 Reference Design”. XMOS has one of the best (most informative) web sites on this technology:
Watch the well-produced video on this page for a quick education on USB audio and related technology:
You can’t buy the XMOS from usual sources, but electronics-parts supplier DigiKey has it avail for $148:
>> Swiss-based ABC-PCB has 24/192 USB audio interface here:
(full manual here: http://www.abc-pcb.com/abc_docs/U2S192-DS-102E.pdf)
This is a PCB with I2S and SPDIF out. Radio Shack has small boxes that one can stuff this PCB into, almost rendering it Plug-n-Play like Halide. Not sure on the $$. Methinks it will be similar to XMOS.
>> Canada’s exaDevices offers a somewhat pricey (USD 430.00) but very high-rez (“384 kHz 32bit low-jitter bit-perfect performance“) USB-to-I2S converter: If you’re not into DIY or a product engineer, this is not for you. It’s noteworthy for its purported high-rez processing.
Some more info: "USB-Interface: Modern USB audio interfaces are USB audio class 2 compliant. Asynchronous mode, external clock and galvanic isolation are the things to look for." is here:
USB-SPDIF (or USB to I2S or EIAJ) converters to avoid:
Diyparadise.com Monica USB and Black Crow. These devices are coupled to the Monica/Mojo NON-oversampling (NOS; aka zero OS) D/A processor (all based on the antiquated Philips TDA1545 DAC chip). Bottom line: Bad design, bad implementation, not asynch, and low-rez. JA's measurements of NOS processors should be reason enough to avoid them!