When I reviewed the Bel Canto DAC 3.5 VB in Issue 216 I found it to be an outstanding full-featured DAC/ preamplifier that only lacked a USB interface. Bel Canto’s thinking was that USB interface technologies were advancing so rapidly that any USB solution included in the DAC 3.5 VB would soon be eclipsed by the next generation of external USB interface devices. So Bel Canto offered an external 96/24 USB converter.
During the intervening time period, Bel Canto’s thinking was proven correct—USB interfaces have continued to improve— and now that the technological dust has settled somewhat, Bel Canto has introduced three separate USB interface boxes. While they all share the same core design, the three boxes differ in interface options and power-supply implementations.
Bel Canto’s least-expensive USB interface device is the $375 mLink, which has a USB input and a lone BNC-terminated S/ PDIF output. Like all the Bel Canto USB converters, the mLink supports up to 192/24 PCM via USB 2.0. The $675 Bel Canto uLink is also USB buss-powered and includes an AT&T ST-Type glass optical output as well as a BNC S/PDIF. The top-of-the- line $1495 REF Link is the only Bel Canto USB device that uses a dedicated low-noise external power supply and adds an AES/ EBU output in addition to a BNC S/PDIF and ATT glass optical.
Both the mLink and uLink share the same size enclosures, and except for the differences in color (the mLink is black and the uLink is silver) and outputs, the two units appear identical. Since they both get their power from USB and weigh well under a pound, they are ideal for someone looking for a completely portable USB interface. The REF Link is substantially larger and has the same footprint as Bel Canto’s other half-width components. The Ref Link also has a knob that lets you change the display from bit-rate to firmware version to off. Due to its size and integral AC power supply (the mLink and uLink are powered through the USB buss), the REF Link is the only Bel Canto USB box that is not readily portable.
Shared and Proprietary Technologies
After spending some time with the Bel Canto units I had some technical questions for John Stronzer, Bel Canto’s designer. My first was how much technology was common to all three devices. According to John, “The 500MHz USB processing core daughter-card is shared on all three Links as well as the S/ PDIF output circuitry. The mLink and uLink are very similar in sharing buss power and overall power-supply architecture. The real difference is in the quality of the clocks. The mLink uses Low-Phase-Noise clocks, while the uLink uses the new Ultra- Low-Phase-Noise clocks. The REFLink also uses Ultra-Low- Phase-Noise clocks and adds further isolation and low-noise internal power supplies, plus galvanic isolation between the USB processing core, the clock, and output electronics. No power is drawn from the USB buss.”
The Bel Canto Web site has several technical papers and FAQs about the USB Links. The published graphs show exactly how low-noise Bel Canto’s clocks can be. The three Bel Canto USB boxes also meet USB 3.0 specifications.