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PCB N°.2 is the decoder/logic board whose functions the maker itemizes as: "S/PDIF receiver, I²S routing, optional SRC, USB transceiver, Superlink interface, I²C-bus to control nearly all chips, micro controller for the entire DAC, user interface and an armada of voltage regulators and gyrators to minimize distortion (each function gets its own set)." Actual conversion occurs on PCB N°.3 via two BurrBrown PCM1792 chips whose outputs encounter a so-called current injection module. That's a discrete I/V converter by company boss and chief developer Carlos Candeias. It creates a balanced voltage for the equally balanced LEF output stage. That's another Candeias invention. This load-effect-free "cascaded single-ended class A circuit with current assist" runs a main transistor at its optimal load-line bias whilst auxiliary transistors coupled through a servo perform the heavy lifting particularly with regard to delivering current into the load.

All the way over to the right PCB N°.4 is the preamplifier board with its conventional non-DIGM attenuation by way of a digitally actuated resistor ladder situated inside a Maxim chip. Turning our attention to the fascia, one notices further unconventionalities. The buttons to the right of the volume control—source, mute and dim—don’t warrant commentary but the four to the left do. 1/ is a choice of ‘flat’ or ‘pulse’ digital filters. The former is a typical linear phase affair, the latter an apodizing variant which minimizes pre-ringing but causes a minor treble roll-off typical for such filters. B.M.C.’s Manfred Penning is a dedicated ‘pulse’ listener but admits that it’s a matter of taste and ancillaries. 2/ switches between 32 times and 128 times oversampling. 3/ activates an upsampler which depending on source and jitter content can be a useful idea says Penning. With B.M.C.’s own transport this option gets defeated however since the I²S Superlink interface is the most direct and best way to supply the DAC with data which renders upsampling obsolete. 4/ can boost the output voltage by 3dB which depending on amplification may be sonically advantageous.

A machine like B.M.C’s DAC1 offers much grist for the old hearing mill since it’s both DAC and preamp and—if one already is or will be legacy listener—part of a pretty advanced transport/DAC combo. My assessment focused on the converter function which will be most interesting for our reader. But I’ll cover the other two aspects in passing. Before I get serious I of course played a bit with different digital inputs, sources, cables, two media players and the digital filters and up/oversamplers. To start at the end, it’s lovely if you can press a few buttons and accomplish audible optimisation. In my setup I was simply handicapped to not hear anything decisive. I could thus live without any of those buttons. Which isn’t to say someone else might not enjoy them. I simply obtain greater returns from swapping USB cables. And that exercise in my book already belongs into the ‘minor tweak’ category of subtle differences. The only thing I was fairly sure of? I didn’t fancy the upsampler. Voices without it seemed more embodied. But since I was mostly immune to the charms of the digital options, I left them standard – apodizing filter, oversampling low, no upsampling.

Aside from B.M.C.’s own transport which I’ll get to, the DAC saw itself leashed to the following: a Squeezebox, a Luxman D-05 SACD/CD deck, two laptops plus a digitally tapped dock-seated iPad2. The latter was a very interesting solution which colleague Jörg previewed in essence three years ago with Wadia’s docking station. I had Teac’s new €249 DS-H01 on hand from which an S/PDIF cable connected to the DAC1. iPad seated, I started the PlugPlayer app which turned the tablet into a media renderer, meaning it retrieved tracks from my NAS server via WLAN and spit them out digitally which the Teac dock transferred untouched. The results were distinctly enjoyable!

While I thought that my notebooks were a tad more natural and self-assured in the vocal band, this impression was subjective and ultimately matter of taste. The ultra-taut bass of the dock solution really was something else. It’s thus a very viable alternative particularly for those who dislike computer shyte next to their hifi or simply prefer tablets to laptops. The Teac dock includes remote control to skip tracks from the faraway couch. Since I don’t care about the looks of my hifi crib, I preferred the iPad in my lap as remote for the notebook. It’s simply more convenient yet. Plus I could simultaneously surf to perhaps enjoy background intel on a band I was listening to. This setup—iPad remote for the laptop server—is in fact how I spent most of my time with the DAC1. More accurately, the laptop accessed my external hard disc via LAN, the media player was predominantly JRiver and the USB cable of choice was by Aqvox. So how did it sound?

In a very different context, colleague Jörg recently quipped something about transitioning from Lego Duplo bits to their standard-sized bobs. And that hits the nail pretty well again. After all, the differentiation of different sounds is well within the purview of far cheaper gear. In the eternal chase for diminishing fractional improvements—at least for me—the question becomes one of differentiation of the individual sound. How well is its temporal progression of attack, sustain and decay rendered? How does seemingly tertiary stuff like the unintentional rawness inside a voice, a careless string snap, a leaky embouchure of a sax player become not merely audible but how is it presented - on a silver tablet, overshadowed or simply integrated and present?