Digital Processor Reviews

The greater my own longevity, the more I admire that very quality—longevity, that is. An "upgrade path" is similarly appealing—if, regrettably, rarely available to humans, who are stuck with the equipment we were born with, give or take a prosthesis or two.

Hi-fi upgrades are less rare than upgrades for us humans, and yet they are far from common. A realistic, practical upgrade path is a factor I consider in any hi-fi purchasing decision—not the only factor, certainly, but an important one. A product that's upgradeable can stay in your system—your audio system—for a long time.

Bricasti Design introduced its first consumer audio product, the M1 D/A converter, in 2010. More than a decade later, a revised version of that DAC continues in production—actually, three different versions, from "Classic" to "Limited Gold"—alongside an expanded array of other Bricasti components, some aimed at audio consumers, others at audio professionals. The consumer-focused M1 remains a favorite, especially for the technically inclined.

I have owned the SE version of the Bricasti M1 D/A converter for several years. It's my reference DAC. When, recently, I became aware of the availability of the factory-installed MDx Processor Board upgrade, I packed up the M1SE and sent it off to the Bricasti factory, which is in Shirley, Massachusetts, northwest of Boston. The factory-installed MDx upgrade costs $1000—a lot less than the $10,000 it costs today to buy a new M1SE with the MDx board.

A complex upgrade history
Almost a decade has passed since John Marks wrote the first report on a version of the dual-mono, three–power-supply M1 in The Fifth Element #67 (footnote 1); John Atkinson reviewed and measured the DAC a few months later. Since then, the M1 has seen some significant improvements, including the addition of a USB input, support for DSD (over PCM), upgraded power supplies for the analog sections, the addition of a standard remote control, and new reconstruction-filter options. The Special Edition (SE)—the version I bought years ago—includes Stillpoints feet, which, thanks to their vibration-absorbing abilities, are said to provide "a more transparent sonic presentation." The SE model adds point-to-point wiring, capacitor upgrades, and a variety of new software features. An Ethernet module is available as an add-on.

Today, the SE's exterior remains largely unchanged. It's a hefty, full-rack-mount unit with thick aluminum panels. The front panel holds a display, a single rotary control knob, six control buttons, and a power/standby switch. As already mentioned, the M1 has three power supplies. It runs hot, as JA noted in his measurements, so make sure you've got ample room for ventilation.

Inputs include AES/EBU (XLR), S/PDIF (one each, RCA and TosLink), and—as mentioned above—USB (Type 2). Outputs are the usual pairs of balanced (XLR) and single-ended (RCA). The control knob on the front panel, and also the remote control, allow for easy playback-level adjustment, so you can run the M1SE directly into a power amplifier, although this adjustment changes the output level in 1dB increments—not as fine as most preamplifiers. Separate L and R pots allow you to adjust the maximum level for the balanced outputs from +8dBm up to +22dBm; the unbalanced outputs are fixed at 2V at full scale.

If you were to take the top cover off the M1 and look down, you'd see three main sections. On each side are the left- and right-channel analog boards and their power supplies. A central section contains the new MDx digital board, with its own power supply.

I asked Bricasti President Brian Zolner to describe the changes incorporated into the new module, pictured above. "The MDx is the new core for all our source products, updating to a newer DSP processor from Analog Devices, the ADSP-SC584 SHARC dual-core processor. ... We updated the USB to accept higher data rates, and the PCB layout was changed to allow for better routing and clocking on all inputs. Jitter in the audio band is extremely low. The MDx Processor board executes oversampling and performs syncing and clock functions between the two analog channels, buffering data and reclocking their separate DACs." The physical isolating of the digital processing section from the analog sections is said to contribute to low noise performance.

I run my system balanced except for the single-ended cable from the turntable to the phono preamp. My CD transport sends over the ones and zeros via a (balanced) AES/EBU cable, and my Mac sends its own digital data by USB. The M1's display panel shows what format it is currently receiving; it also keeps track of "digital overs," if any occur, although it doesn't correct them (footnote 2).

I asked Zolner to remind us why balanced and dual-mono designs are a good thing: "Balanced is always better. It lowers the noise, and in our case the actual DAC output is differential, so the complete analog signal path is balanced, not just creating a balanced output. Dual mono is a challenge in a DAC, as each channel has its own clock synchronization, which is what the SHARC processor receives and re-clocks. Plus, here there are two DACs with two power supplies for more current—sort of like monoblock amps."

Setting the bar higher
"Many things that contribute to the sound character of the M1 are analog," Zolner told me. "How traces are routed on the PCB, the thickness of them, the material of the PCB, the electrolytic capacitors used, the type of op-amps, and the power supplies, which are all linear."

Not long ago, the bar was set low for digital gear. The best many people hoped for was that their DAC or digital player be nonfatiguing: If you aren't exhausted by the time you finish listening to The White Album—well, is that really the best we can hope for? It took years for high-end digital hardware to be able to deliver on the yin/yang (or yang/yin) of detail without harshness, but we are in an era now when this goal is possible—indeed, an everyday reality.

One reason digital has improved in recent years is that digital recording and sound reproduction have improved. Part of this is jitter reduction. In his informative article "A Case of the Jitters," John Atkinson explains what jitter is and what can be done about it: "There is no consensus about what levels of jitter in a digital product's output are acceptable; the audibility will depend on both level and spectrum" (footnote 3). The Technical Specifications for the Bricasti M1SE state a rating for jitter of 8ps at 48kHz and 6ps at 96kHz. These are very low numbers; you can see much higher numbers present in a number of earlier generation DACs.

When I first listened to the Bricasti M1SE with the new MDx board installed, I heard some subtle but important differences from what I had experienced prior to the upgrade. Details of timbre and soundstage exactitude increased but without any increased brittleness or etching. Bass seemed firmer, and the clarity of musical transients improved. I asked Zolner why this might be: "This is a result of the change in clock timing that was improved with the MDx board. This is a digitally controlled circuit. The MDx makes hardware changes to improve this even further. Jitter in the audio band is very low, so that might account for the lack of harshness you are hearing."

Choice among competing component brands and designs is the true big picture for audio consumers. But there is another level of selection within the Bricasti M1SE MDx, which affects the sonic performance. Fifteen distinct oversampling filters can be chosen from the menu via the front panel control knob or the remote control. "The main difference is the type, Linear or Minimum," Zolner said. Nine of the filters are linear phase and six are minimum phase. That's an uncommonly large number of filter choices—but there's more: Each of those filters has options, such as when the filter starts and ends and how much attenuation it applies. Zolner says that he prefers the minimum-phase filters.

I checked the online gossip from M1 users. Minimum Phase filter #2 seemed to be the favorite. This is my pick as well. This filter seems to me the most realistic and pleasing with most music and with my system.

The many senses
To use a cooking metaphor: Different D/A converters bring different flavors.

I agree with my colleague Herb Reichert, who wrote recently that "the odds against two manufacturers' DACs ... sounding exactly the same are extremely large."

Eye trouble sent me to an ophthalmologist a few months ago. Along with very high-tech scanning devices, they used the old "Can you read the third line?" rig as they switched out lenses. That's my metaphor in this review: Changing a DAC gives you a different aural "lens" through which the music is filtered. When the lens is different, you see different things.

There is a moment in an eye exam when the optometrist (or ophthalmologist if you're fancy) asks "How about now?" When it clicks and things become clearer, there is a visceral sense of relief and relaxation. So it has been for me with the Bricasti M1SE MDx.

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Footnote 1: John Marks also took several more looks at the M1; those examinations start here.

Footnote 2: See the description of "intersample overs" in Jim Austin's review of the Benchmark DAC3 HGC.

Footnote 3: Experts I've spoken with lately have said that today's digital designers are concerned about far smaller jitter amounts than in previous eras—amounts so small that special equipment is required to measure it.—Editor