Equipment Reviews

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

When I first laid eyes on the Director Mk2 preamplifier-DAC from Sound Performance Lab (aka SPL), it reminded me of a military-spec ham radio. Small yet built like a tank, it sports at the center of its faceplate a large Volume knob. At upper left is a small, red dot-matrix display, and at upper right two needle VU meters and a Standby/On toggle. At lower left is a smaller knob for selecting Mute or one of its 11 inputs, and at lower right are two toggle switches, labeled Tape Monitor Off/On and VU. The Director Mk2 is small—11″W x 4″H x 11.8″D—and weighs just 13 pounds, yet somehow exudes presence. In my many years of reviewing audio equipment, I’ve never seen such a small yet intriguing-looking preamplifier-DAC. It costs $3599 (all prices USD).

Subtly sophisticated

The Director Mk2’s 1/4″-thick faceplate, available in silver, black, or red, is clearly labeled in contrasting text in a color dependent on the finish. The large, heavily weighted, motorized volume knob that turns the Alps RK27 Big Blue analog potentiometer behind it has a silky-smooth action, and a tiny red LED to indicate where on the “clock” the volume is set. The little display reads “IN” accompanied by the corresponding number (1 through 6) of the analog input selected. Digital inputs are displayed for about two seconds by input name (USB, AES, Coax, Optic, Remote), after which the first letter of that name appears along with the incoming signal’s sample rate: e.g., U384 for USB 384kHz, or O192 for optical 192kHz. When a DSD signal is detected, the screen displays “DSD” plus its multiplier: DSD1 for 64x, DSD2 for 128x, or DSD4 for 256x. The Director Mk2 does not decode DSD512.

The input knob is nicely weighted and aggressively notched for each input. The backlit VU meters display the range of input level from -20 to +5dB, but they’re small—you need to be pretty close to them to read them. SPL is proud of these meters’ accuracy; a blurb in the manual points out that 0dB corresponds to +4dBu, and that “The time calibration of the VU meters complies with the requirements of the BBC. The rise time up to 0 dB is about 300 ms.” Depending on your habitual listening level, you can lower the sensitivity of these meters by 6dB or 12dB, using the three-position toggle switch below the right-hand V/U meter. (The toggle’s central position is 0dB.)

The rear-panel real estate is sparse but efficiently apportioned. Beginning at top left and moving clockwise: First is the mains rocker switch and a 115V/230V toggle, then two 12V trigger outputs for powering connected amplifiers up and down, then two Neutrik inputs (XLR) for connecting balanced analog sources, then the four digital inputs: AES (XLR), coax (RCA), optical (TosLink), and USB. We begin our leftward journey: Directly below the digital inputs are four pairs of gold-plated RCA jacks for unbalanced analog sources. Then come Left and Right Send and Return gold-plated RCA jacks for the Tape Monitor, accompanied by a boost button (-10dB Send, +10dB Return), for leveling the input and output sound levels. Two more gold-plated RCA jacks provide Direct Output (this bypasses the volume control), to provide full-gain signals to an external input such as a headphone amplifier. Then come one pair of balanced outputs (XLR; there are no unbalanced outputs) and, finally, a small button labeled Learn IR-Remote (more about this below).

But it’s what’s between its front and rear panels that makes the Director Mk2 unique, as I discovered when I removed its well-ventilated case of stamped steel to take a closer look. I was pleased to see that every inch of space has been used. My eye was immediately drawn to the fully shielded, custom, toroidal (donut-shaped) transformer mounted vertically on the right side of the interior. I could see two independent windings emerging from the transformer, one each for the analog and digital circuits, both featuring their own rectifiers and linear regulators.

Directly in front of the transformer are ten 1000µF EPCOS capacitors for filtering the DC voltage for what may be the most unique feature under the Director Mk2’s hood: SPL’s proprietary VOLTAiR technology. In a nutshell, line-level audio components with linear power supplies use transformers to step down the wall voltage; rectify, filter, and regulate the voltage, typically to +/-15V DC; and finally, feed the cleaned power to the other components (op-amps, etc.). Believing that passing along signals at a higher voltage can improve the quality of the signal, SPL designed their proprietary Supra op-amp to maintain the ±60V (120V rail). SPL claims that this approach provides more headroom and dramatically improves dynamic range while producing significantly lower levels of noise and distortion.

SPL claims that the Director Mk2 produces only 0.000992% THD (0dBu, 1kHz), and has a dynamic range of 135dB and an A-weighted noise specification of -102.5dBu. However, these specs aren’t solely the result of the VOLTAiR technology. Considerable care and attention were paid in designing the Director Mk2’s analog and digital signal paths. Analog signals enter through the input connectors and are passed along to the input-selection stage. From there, signals are sent to the active volume control and then to the output stage, with a final stop at the mute relay before exiting through the output connectors. Short and unadulterated. The Director Mk2 was designed to provide 0dB of gain, so if you use low-output analog sources and/or need to drive a low-gain amplifier, ask your dealer for a test drive before buying.

The digital signal path is a bit more complicated. Digital signals go straight from the input connector to a Programmable Field Gate Array (PFGA) that then feeds them to the DAC chip, an AKM AK4490. The DAC converts both PCM and DSD signals (up to 768kHz and DSD256, respectively) to analog, after which, depending on their original format, they’re directed to one of two corresponding DLP120 low-pass filters incorporating VOLTAiR technology. At the other end of the filter, the signal is sent to the volume control for attenuation. After that, all signals follow the same analog path to the output jacks.

I was told that close attention was also paid to ensuring the shortest possible analog and digital signal paths and the highest-quality parts. This involved comparisons and tests of prototypes and components, evaluations of various circuit configurations, and many hours of listening tests and further tweaking. The result is two layers of circuits laid out on independent, high-quality boards with copper traces, Panasonic PAM Gold capacitors in the analog path, Styroflex caps used throughout the DLP120s, and the discrete op-amps and volume pot. Attention was also paid to selecting DAC chips to ensure that the chip chosen would not only work with but complement SPL’s VOLTAiR technology. This meant that SPL was very rigorous in their requirements that the DAC provide a wide dynamic range, low distortion, and ultra-low levels of noise. One of the key advantages of AKM’s AK4490 chip, other than its ability to support up to 768kHz PCM and DSD256, is its unique Over Sampling Ratio Doubler (OSRD) technology, which, AKM claims, helps reduce out-of-band noise. The synergy between SPL’s technologies and key OEM parts, and the elaborate testing of the latter, tell me that SPL did a lot more than select a bunch of high-quality parts, wire them together, put them in a fancy case, and slap a price tag on it. Instead, they designed, from scratch, a product whose parts and technology complement each other, to result in something greater than the sum of its parts. That’s not easy to do.

Of the manual’s 20 pages, half are filled with large, easily understood illustrations; the rest describe basic operation in a large, easily read font. In short, if you’ve ever used a preamp-DAC before, you can throw the manual back in the box—you won’t need it. The dot-matrix display, while basic, is easy to read from across the room.

SPL has cleverly chosen not to provide a remote-control handset. Instead, the Director Mk2 can learn the input-selection and volume up/down codes of whatever infrared remote(s) currently haunt your media room. Programming happens with a press of the Learn IR-Remote button on the rear panel—once the first code is learned, the Director Mk2 prompts the user to keep programming volume and input commands until all four codes are learned. I found that this feature worked most of the time—the Director Mk2 quickly learned codes from the dedicated remotes of my Anthem AVM 60 surround processor, Cisco cable box, and Oppo BDP-103 universal BD player, but refused to learn anything from the remote of my reference preamplifier, an Audio Research Reference 6SE.

Setup and system

Inserting the SPL Director Mk2 in my system was as easy as removing my ARC Reference 6SE preamp and swapping out interconnects. I also added a second Analysis Plus USB link to feed a digital signal to the Director Mk2, as I do with my PS Audio DirectStream DAC. The rest of my reference system remained untouched: Kimber Kable KS 1116 balanced interconnects linked the Director Mk2 to a pair of Classé Audio Delta Mono power amplifiers, the PSA DirectStream DAC, Musical Fidelity’s M6x phono stage, and my Pro-Ject RPM 10 Carbon turntable with Sumiko Starling cartridge. Kimber’s Select 6063 speaker cables linked the Classé monoblocks to my Paradigm Persona 7F loudspeakers, and a Torus AVR 20 power conditioner provided power to everything via Clarus Crimson power cords. My sole digital source was an Intel NUC computer running Windows 10 and Roon. All digital cables were from Analysis Plus.

The Director Mk2 as preamp

Because the Director Mk2 is an analog preamplifier and DAC, I wanted to evaluate its two sections independently. The first section of listening observations is an evaluation of the Director Mk2 used only as a preamp. I kicked things off by using my PS Audio DirectStream DAC as a digital source connected to the analog inputs of the Director Mk2 with Kimber Select KS1116 balanced interconnects. I set the SPL’s volume to 50% with no music playing, put my ear nearly against the tweeter of one of my Persona 7Fs, and heard almost nothing. The Director Mk2 eclipsed even Ayre Acoustics’ KX-5 Twenty preamplifier, which in November 2015 I called “the quietest preamplifier I have ever reviewed.” Leaving the volume at just a tick under 50%—equivalent to my usual listening level of “35” on my ARC Ref 6SE—I cued up “The Look of Love,” from Diana Krall’s Live in Paris (24-bit/96kHz FLAC, Verve).

When I reviewed SPL’s m1000 mono amplifiers, I found the sound a few degrees on the warm side of neutral. Not so with the Director Mk2—it sounded neutral, clean, focused, and transparent. An acutely focused image of Krall’s voice appeared at center stage, as expected, and I appreciated the timbre and weight of her deftly played piano. I was a bit surprised that the decays of notes seemed shorter than I’m used to hearing, and that John Clayton’s skillfully plucked double bass was a bit more forward in the mix than I recalled. However, this brought forward the textural nuances of the bass strings, which I quite enjoyed. I also liked hearing Jeff Hamilton tapping his drums in the background. Still, why weren’t those decays longer? After all, the Director Mk2 didn’t seem to be subtracting anything else from the sound picture. I needed to dig deeper.

In “Slow Burn,” from Kacey Musgraves’s Golden Hour (16/44.1 FLAC, MCA Nashville), her strums on acoustic guitar were crisply delineated, with quick transients and inviting realism. Again, the Director Mk2’s sound was tremendously focused and agile; Musgraves’s voice was etched at center stage, ripe with textural detail and surprising density. As I listened, I was so impressed by the clarity of images, depth of field, and ease with which the Director Mk2 communicated music that I had to stop and reconfirm its price. Yes, still $3599. I played “Slow Burn” again.

This time I was drawn to the punchiness of Daniel Tashian’s bass guitar and how effortlessly yet precisely it was layered into the mix. I also have this album on LP; I switched the Director Mk2 to its second balanced input, turned on my Musical Fidelity M6x Vinyl phono stage, and dropped the needle. The Director Mk2 immediately highlighted the differences between these analog and digital mediums. Tashian’s bass was markedly less prominent on vinyl, yet Musgraves’s voice was even more present, more smooth in texture, more “in the room.” Her acoustic guitar was also brought more to the fore, and the soundstage was widened and deepened by about 2ʹ. All of this was enjoyable in its own way; more important, the Director Mk2 did nothing to hide or diminish any of these subtle differences in sound.

The Director Mk2 as DAC

Impressed with the SPL’s performance as an analog preamplifier, I was now eager to assess its D/A section. To activate those circuits, a driver must be downloaded from SPL’s website, and for whatever reason, installing this driver on my Intel NUC computer running Windows 10 buggered up the configuration of my PS Audio DirectStream DAC, leaving me with no audio output from the NUC. Uninstalling and reinstalling the PS Audio’s driver and a couple of reboots solved the problem, and Roon picked up the Director Mk2 seamlessly. All I then had to do was configure Roon to run the Director Mk2 as a second zone. I was set for a good ol’-fashioned head-to-head comparison.

Well, almost set. First, I familiarized myself with the Director Mk2’s sound when working as a DAC and preamp to drive my Classé Delta Mono power amps. The sound of the Director Mk2 when fed a digital music signal was, in a word, unveiled: highly dynamic, transparent, vivid, and powerful. Andy Newmark’s drums in “True to Life,” from Roxy Music’s Avalon (24/96 FLAC, Virgin), were re-created in my room with tangible impact—and I enjoyed the spaces between those drums, Bryan Ferry’s voice, and Neil Hubbard’s guitar, the image of which appeared at the far left of my room. I’ve listened to this album countless times through more components than I can count, and rarely have instruments, voices, and percussive effects sounded so well layered yet spaced so distinctly apart and individually dynamic. I especially enjoyed the opening seconds of “Take a Chance with Me” as Hubbard and Phil Manzanera fill the soundstage with eerie sounds from their masterfully manipulated electric guitars. Though Ferry’s keyboard filled the center of the soundstage, it was eclipsed by Newmark’s drums, which slammed out with more body and weight than I’ve heard.

Playing “Water of Love,” from Dire Straits’ Dire Straits (16/44.1 FLAC, Vertigo), with the Director Mk2’s volume knob at 10 o’clock (equivalent to about 28 on my ARC Reference 6SE), I immediately appreciated how open and airy the woodblocks in the opening seconds sounded. Their decays lingered in the air as they were tapped throughout the track, complemented by Pick Withers’s hard-hitting drums. As Knopfler enters at center left on acoustic guitar, I was drawn to its sharply plucked strings and the implication of tension. John Illsley’s bass-guitar notes were conveyed with convincing weight and density, and just a wisp less presence than Knopfler’s strings. I didn’t recall hearing this juxtaposition quite as convincingly at lower volumes through my reference DAC, PS Audio’s DirectStream, so I hit Pause, switched Roon zones, and began comparing.

So far, SPL’s Director Mk2 had set the bar high for any sub-$5000 preamp-DAC, so I had no qualms about any unfairness in such a comparison, despite the DirectStream costing nearly twice as much ($6899). Beginning with “Water of Love” on pause in both Roon zones, I listened first to the PSA, then to the SPL. Differences were immediately apparent: the DirectStream sounded warmer. Mark Knopfler’s voice was smoother in texture, and Illsley’s bass notes were a bit better resolved yet lacked smidgens of the body and weight I’d heard through the Director Mk2. Conversely, the SPL’s DAC quickly proved more dynamic and exciting: Knopfler’s acoustic-guitar plucks were more visceral and thus more captivating. The SPL was also quieter, aural images appearing on the soundstage against a “blacker” background. This helped highlight microlevel details that I struggled to hear through the PS Audio and helped to give an impression of greater space between instruments and voices on the stage. Overall, I was drawn more into the music by, and wanted to listen to it longer through, the SPL.

Until I turned the volume past 11 o’clock. At that point the sound began to become a bit steely and a hint too expressive. The dynamic inflections I’d loved through the SPL at normal listening levels now became a tad shouty, and could at times turn into too much of a good thing. The PS Audio’s warmer, smoother sound let me listen to music as loud as I dared without worrying about listening fatigue—as I turned up the volume, the sound simply kept blooming without ever sounding bloated, compressed, or unbalanced.

The only analog preamplifier I had on hand was my Audio Research Reference 6SE ($17,000). In terms of transparency, bass articulation, dynamics, and neutrality, the Director Mk2 was comparable with the ARC. Perhaps due to its overall more lucid sound, it fell short in terms of bloom, warmth, textural fluidity, and sense of dimension. Still, the quality of sound offered by the Director Mk2 was damn impressive for a preamp that also includes an excellent DAC and costs a good bit less than one-fourth the Reference 6SE’s price.

Summing up

At two or even three times its price of $3599, SPL’s Director Mk2 would still be an outstanding preamplifier-DAC. Well built and meticulously designed, with straightforward source selection and volume control, and able to learn command codes from the remote controls you already own, it’s an ergonomic dream. And in terms of sound quality, I found nothing to complain about and much to praise: The Director Mk2 was vanishingly quiet, dynamic, neutral, and exceedingly communicative of the music, particularly in the lower frequencies.

SPL’s Director Mk2 is, in a word, spectacular. If you’re in the market for a preamp-DAC, I highly recommend that you audition it—you might find just what you’re looking for, at a price thousands of bucks lower than you expected to spend.

. . . Aron Garrecht
arong@soundstagenetwork.com

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

Associated Equipment

• Speakers: Paradigm Persona 7F
• Subwoofers: JL Audio Fathom f112 (2)
• Amplifiers: Classé Delta Mono monoblocks (2), Parasound Halo A 51 (multichannel), SPL Performer m1000 monoblocks (2)
• Preamplifiers: Anthem AVM 60, Audio Research Reference 6SE, Musical Fidelity M6x Vinyl phono stage
• Digital-to-analog converter: PS Audio DirectStream with Bridge II network soundcard
• Sources: Oppo Digital BDP-103 universal BD player; Intel NUC computer running Windows 10, Roon; Pro-Ject RPM 10 Carbon turntable with Sumiko Starling cartridge
• Interconnects: Analysis Plus (digital), Kimber Kable Select KS-1116 (analog)
• Speaker cables: Kimber Kable KS-6063
• Power cords: Clarus Crimson
• Power conditioner: Torus AVR 20

SPL Electronics Director Mk2 Preamplifier-DAC
Price: $3599.
Warranty: Five years parts and labor.

SPL Electronics GmbH
PO Box 1227
41372 Niederkrüchten
Germany
Phone: +49 (0)2163-9834-0
Fax: +49 (0)2163-9834-20

Email: info@spl.audio
Website: spl.audio