This review page is supported in part by the sponsors whose ad banners are displayed below

This review first appeared in the March 2012 issue of hi-end hifi magazine of Germany. You can also read this review of the B.M.C. DAC1 in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio or B.M.C. Audio - Ed.

Reviewer: Ralph Werner
Sources: VPI Scout II, SME MS  12-inch, VPI JMW 9T, Denon DL-103, Ortofon MC Rondo Bronce, Zu Audio DL-103, SAC Gamma Sym, Luxman D-05, Logitech Squeezebox 3, Readynas Duo, HP Notebook, Benchmark DAC1 USB, NorthStar USBdac32
Amplification: Octave HP300 with phono, Electrocompaniet AW 180,  Denon PMA 2010AE
Loudspeakers: Ascendo System F, Blumenhofer Fun 13, Thiel SCS4
Sundry accessories, cables and racks
Review component retail: from €3.198 to €3.798 depending on featurization

Today’s tester is advertised as "command central for a complete BMC chain". This might have a few readers wonder. Why then is it called DAC1? Yes converters are widely fashionable and popular - but how does that turn 'em into control centers for hifi systems? Here the term actually fits. B.M.C. Audio’s machine isn’t mere converter. It's also a preamp particularly when fully optioned out as reviewed, i.e. with USB input and preamp module. The latter adds two analog RCA and one XLR input plus a variable XLR output. But it's a preamp not only then.

We’re already off to the races so back to the beginning. As will be clear by now, this is a modular platform. You can acquire the DAC1 with/without USB or preamp board to stretch the sticker from €3.200 to €3.800. Which begs the question how a DAC without preamp board can still serve as preamp. Here it can under two provisos: 1/ you merely need digital inputs; and 2/ you run a B.M.C. amplifier. Volume control with the DAC1 doesn’t require the preamp module. But then it only works with its stable mate amps – via two optical connections. Yep, not your grandfather’s Victrola then. Team B.M.C. pursues its own thinking and volume control is one area where they beg to differ. They do so with ‘Discrete Intelligent Gain Management’ or DIGM for short. The basic idea behind it is so simple yet elegant that one wonders why others haven’t embraced it.

Instead of amplifying the signal inside the preamp—or more precisely attenuating it which is what most preamps these days do with sources—it leaves the DAC1 at a fixed level. Simultaneously a trigger signal departs via the optical fiber links. This trigger now manipulates the amplification factor of the power amp directly. This elimination of redundant gain stages and its concomitant reduction of distortion and noise plus a much shorter signal path all pay great sonic dividends says the maker. Sounding attractive in theory we might test this scheme in practice at a later date. Today our focus is on the DAC1 as a ‘conventional’ preamp. I simply wanted to mention the DIGM feature since it is a central solution for any complete B.M.C. system. (Those interested in their integrated amp might want to read our prior review.)

Checking up on the business end might cause the next question mark. ‘Wow, nine digital inputs. But why five of ‘em via BNC?’ Actually the DAC1 Pre HiRes USBII—that’s the mouthful for the fully tricked out version as reviewed—only runs six, not nine digital inputs. There are three S/PDIF (coax, BNC and Toslink) and one each AES/EBU and USB. The other four BNCs together from the ‘Superlink’. This is a so-called I²S interface for the firm’s matching CD transport. The core difference to the ubiquitous S/PDIF and also AES/EBU standard is that the clock signals aren’t sent down the same wire as the audio data. S/PDIF requires coding on the send side and decoding on the receive end. I²S uses discrete conductors for the bit clock, left/right clock, master clock and actual audio data. The advantages according to B.M.C. are significant:

I²S not only eliminates the code/decode stages with their issues but more importantly the reconstruction of the sampling frequency in the PLL of the DAC receiver where it becomes a typical jitter generator. The notion to apply the I²S specification originally written for internal communication (Inter-IC Sound Interface) for external signal transfer is sadly applied very rarely today. Besides B.M.C. Audio I can only name five other makers off the top of my head – North Star Design, PS Audio, April Music, Ancient Audio and Zanden. Sad. Sad too is that in typical hifi tradition a global wiring standard for this scheme does not exist. Six makers, four different cables: HDMI for PS Audio, RJ45 for North Star and Zanden, four coax cables with BNC terminations for B.M.C. and Ancient Audio, S-video for April Music. Sigh.

This now covered socketry and connective options. To recap, the analog signal departs the DAC at a fixed level via RCA or XLR; or variable through the preamp module’s exclusively XLR outputs. Let’s pop the bonnet next for a sneak inside. From left to right there are four PCBs. The power supply exhibits a minor forest of yellow dwarves. I counted a total of 31 caps which summed to about 70.000µF of total capacitance. For context one of my mono amps is happy with 60.000µF. Granted that’s per channel but for a DAC it’s a heavy figure. Ditto for the more normally sized 50VA toroidal transformer. These caps are a B.M.C. development by the way and called ‘balanced current’ to indicate that charge/recharge lines exhibit mirror-imaged behavior to suppress parasitic inductance well below what is standard for caps. "In the power supply these parts perform far superior for distortion suppression of mid to high-frequency powerline noise. This creates a lower noise floor and quicker recovery means livelier dynamics" explained the company’s Michael Conrad.