USB-to-S/PDIF Convertors - SOtM dx

SOtM dX £365

USP: Asynchronous 24/192 converter with supplied Windows driver software and optional battery/mains power supply.

The awkwardly named SOtM is from Korea. It is an asynchronous convertor that accommodates 44.1 and 48k sample rates and their multiples all the way up to 192kHz,  with up to 24bit resolution, so this convertor ticks all the boxes. It comes with a USB driver disc for Windows (XP/SP3, Vista/SP2, 7), or will work with Mac OS-X 10.6 (Snow Leopard) onward. Data rate must be set in the Advanced tab of the Sound control panel in Windows.

The small SOtM is USB powered but has an outboard power supply option that alternatively will run it from batteries instead of the computer’s power supply. The batteries are charged from the mains.

S/PDIF outputs are in balanced AES/EBU form via an XLR socket, unbalanced form via electrical output through a phono socket as usual and – unusually – via an optical TOSLINK option as well. On high quality convertors TOSLINK and its need for a transmitter and receiver – potential sources of jitter – is uncommon.

SOUND QUALITY

This two unit affair also shows the importance of taking power seriously. The Chesky download of Rimsky-Korsakov’s 'Dance of the Tumblers' shows that this link has a good sense of control, with good delicacy for the orchestral effects going on. The tambourine starts and  stops well, the strings sound clean, perhaps a bit less present than I have heard on the Weiss playing through FireWire, but a really excellent well-constructed sound with a good solid soundstage. I would put it equal to the Halide Bridge without the extra USB power supply, but not as good with the upgrade. It doesn’t quite have the airiness of the Halide, but seems to do the transients superbly.

This is one of the few convertors to have an optical S/PDIF output. Our measurements showed it worked almost as well as the electrical outputs, uincluding AES/EBU at left.

MEASURED PERFORMANCE

The SOtM produced good if not exceptional figures when fed our  resampled 48k sample rate test signal. Signal related jitter was low at 30pS and the random jitter noise floor low at 6pS. Low rate clock drift was a little higher than the others at 60pS, but still not high. With the un-resampled 44.1kHz CD test signal, signal related jitter improved as expected to 25pS, with clock drift and random jitter as before. The optical output was no sinner at 38pS signal related jitter but XLR was worse at 50pS; the unbalanced electrical connection was cleanest. With the external power supply, mains or battery mode, results were unaltered.

Recording sample rate 44.1/Output sample rate 48k

clock drift 60pS

signal related 30pS

random 6pS

SotM dX £365

SOtM Audio

www.sotm-audio.com