Director MK2
SPL (Sound Performance Lab) is a German company founded in 1983 by Hermann Gier and Wolfgang Neumann. Today, it develops and manufactures innovative products for both the studio and Hi-Fi markets. After decades of designing for the professional audio sector, the company successfully transferred its proprietary 120 V VOLTAiR design language to home audio components—showcasing all its accumulated engineering expertise in its current Hi-Fi line.
Voltair 120V
Although SPL is widely recognized among professionals, it remains relatively unknown to many audiophiles who still associate the brand primarily with studio equipment. I had visited SPL’s booths at several shows before but never had a chance to actually listen to their gear. However, the technical papers I had read about the 120 V VOLTAiR technology left me with the distinct impression that a hidden treasure lay beneath the surface.
That impression turned into conviction during a visit to BL Müzik, when Mr. Levent invited me into the demo room. What I heard there was simply astonishing. It’s difficult to put my feelings from that day into words—the presentation was at once natural, warm, and musical, revealing the true timbre of every instrument with effortless realism.
When we look into the heart of SPL, we find that this sonic character stems directly from the company’s research and development around its 120 V VOLTAiR technology. Let’s take a closer look.
Voltair 120V
120 V VOLTAIR
Before diving into the specifics of SPL’s 120 V VOLTAiR concept, it helps to revisit how a conventional analog audio circuit operates. Let’s first clarify a term that will appear frequently in this discussion.
Supply Rail
An amplifier or operational-amplifier (op-amp) circuit uses an external power source to boost an incoming audio signal. This power supply typically provides both positive (+) and negative (–) voltage rails, whose values define the circuit’s operational limits. For decades, the industry standard has been ±15 V (and in some cases ±18 V). In other words, the circuit’s upper voltage limit is +15 V and its lower limit is –15 V.
Commercially available, industry-standard op-amps such as NE5532, TL072, or OPA2134 are designed to operate safely at ±15 V. Components running at this voltage are inexpensive, reliable, and easy to source. Since a maximum output level of around +20 dBu (≈ 7–8 Vrms) is generally sufficient for most Hi-Fi and studio applications, ±15 V systems have become the de facto “gold standard.”
So why do manufacturers like SPL push beyond this long-established ±15 V boundary? To answer that, we need to understand another key concept:
Headroom
Headroom is the safety margin between a circuit’s nominal operating level and the point at which distortion (clipping) begins. Within this margin, the circuit can handle transient peaks without compressing or distorting them. Music signals often contain brief peaks that far exceed their average level, and adequate headroom ensures those peaks pass cleanly.
A traditional ±15 V circuit can typically remain clean up to about +22 dBu at its input. Yet today’s high-resolution DACs and wide-dynamic-range DSD/PCM recordings can push those limits. As the signal approaches the supply-rail ceiling, the circuit begins to saturate and harden, particularly during large orchestral passages, electronic music transients, or ultra-dynamic recordings. Op-amps that perform flawlessly at moderate levels deteriorate rapidly as they near their voltage limits.
These inherent constraints of conventional design led SPL to create the 120 V VOLTAiR architecture.
Where typical audio circuits operate at ±15 V, SPL’s proprietary SUPRA op-amp modules run at ±60 V, for a total supply of 120 V. Compared with ±15 V designs, the signal “ceiling height” is thus quadrupled, dramatically expanding the circuit’s linear operating range. To realize this groundbreaking concept, SPL engineered discrete-transistor op-amp modules using high-voltage transistors, resistors, and capacitors—all tailored for reliable operation at 120 V.
Dynamic Range
THD&Noise
Thanks to all these engineering achievements, SPL’s 120V VOLTAiR design achieves a headroom margin up to 32.5 dBu without distortion — roughly 10 dB higher than that of conventional circuits.
Because the circuit never operates near its supply rail limits, THD (Total Harmonic Distortion) and IMD (Intermodulation Distortion) remain exceptionally low. The higher supply voltage also improves the signal-to-noise ratio.
Moreover, since greater rail voltage widens the linear operating region of the circuit, transient response becomes both faster and more accurate.
Headroom
Director Mk2
Director Mk2
At first glance, the Director Mk2 measures 30 cm wide and deep, and 10 cm tall. With its rounded corners, solid metal craftsmanship, and analog VU meters on the front panel, it blends nostalgic charm with a modern aesthetic. Don’t be misled by its compact form factor — this preamplifier performs far beyond what its size might suggest.
At its heart lies SPL’s hallmark 120V VOLTAiR supply-rail technology, used not only in the output stage but throughout all preamp and DAC circuits. Yes — you read that correctly: this preamp also houses an outstanding DAC inside, which we’ll explore shortly.
The front panel design is minimalist and purposeful, avoiding unnecessary flashiness. Let’s begin with the volume potentiometer.
SPL equips the Director Mk2 with an ALPS RK27 “Big Blue” potentiometer. When used with the remote control, it operates via motor drive, but it can also be adjusted manually.
The volume knob feels satisfyingly solid — turning it by hand gives that “spoon in honey” sensation (a term I particularly like). The control section is directly tied to the analog ±60 V VOLTAiR rail architecture. The potentiometer precisely adjusts the signal level within this high-voltage circuit. Accurate channel balance is essential in stereo setups, and measurements show deviations to be impressively low.
Director Mk2 Back Panel
The input section offers six analog and four digital sources: 4×RCA, 2×XLR, plus digital USB, AES/EBU, COAX, and OPTICAL. Output options include both RCA and XLR pairs. Via DIP switches on the rear panel, you can configure the Director Mk2 as a standalone DAC or select between RCA and XLR outputs.
Inside, the built-in DAC supports PCM up to 768 kHz/32-bit and DSD up to DSD256, ensuring compatibility with virtually all modern Hi-Res formats. For testing, I used a Rose RS130 streamer and a MacBook as digital sources. The USB connection worked flawlessly, and the DAC locked seamlessly to DSD and various PCM sample rates. But make no mistake — this DAC is nothing like the generic ones found in most preamps. The DAC768v2 inside the Director Mk2 performs far beyond expectations.
DAC768v2 Architecture
The story begins with the Spartan-7 FPGA. In the Director Mk2, this FPGA acts as a digital signal-processing hubpositioned before the DAC chip. It receives input signals from the USB, AES/EBU, COAX, and OPTICAL interfaces, formats them appropriately for the DAC, and manages PCM/DSD routing, digital filters, and clock synchronization.
The key here is that it’s FPGA-based. FPGA (Field-Programmable Gate Array) devices are integrated circuits that can be reprogrammed by the manufacturer or user after production. Containing thousands (or even millions) of logic gates, they can be configured via software to perform complex, customized digital operations.
They’re not processors per se but reconfigurable, application-specific computing fabrics. Brands such as CH Precision, dCS, and Mola Mola (which I have previously reviewed) also employ FPGA-based architectures for the same reason — absolute control over digital signal processing.
AK4493SEQ DAC Chip
SPL uses the AKM AK4493SEQ Velvet Sound chip, known for its low distortion (THD+N) and smooth, “analog-like” tonal presentation. It has a tendency to soften the digital edge, yielding a more natural texture. However, the DAC chip itself has only a minor influence on the final sound; what truly defines the outcome are the output stage and low-pass filter topology.
Headroom +24 dbu
Headroom +18dbu
SPL SLP120 Low-Pass Filter
The low-pass filter removes high-frequency artifacts left after digital-to-analog conversion — and also serves as the stage where DSD conversion takes place. In the Director Mk2, this section was entirely designed in-house by SPL engineers, based on the 120V VOLTAiR platform. Thanks to the wide headroom of this architecture, filtering occurs without introducing extra distortion or dynamic compression.
The result is ultra-low distortion, a vast dynamic range, and — especially in high-resolution playback (DSD256, PCM 768 kHz)** — a presentation that is smooth, detailed, and spacious.
The sonic benefits of using high-voltage circuits are obvious, though it introduces manufacturing challenges that most companies shy away from. Among European manufacturers, only T+A Audio comes to mind, with its HV-series amplifiers employing similar high-voltage rail topology.
SPL Performer s 800
SPL Performer S800
The SPL Performer S800 greets us with an understated yet classic design. Like the Director Mk2, it features an aluminum chassis with the brand’s signature rounded edges and elegant form. However, at 13 kg, it feels considerably more substantial.
SPL’s amplifier design philosophy separates voltage amplification and current amplification into distinct stages, each with its own feedback path — preventing speaker back-EMF from interacting with the input stage.
Voltage gain of 26 dB occurs entirely in the first stage, employing the same 120V VOLTAiR technology throughout. The second stage focuses exclusively on driving the output transistors optimally. All op-amp modules used inside follow the high-voltage topology.
Opening the chassis reveals a massive 850 VA toroidal transformer from the German company Noratel, flanked by 41,000 µF of high-voltage-rated Kemet electrolytic capacitors for supply filtering. On either side of the centrally located power supply are symmetrically arranged output stages. The VOLTAiR op-amp boards face the heat sinks, which also act as natural shields between the transformer and the audio circuits. Once again, VOLTAiR technology takes center stage — and as I’ll describe in my listening notes, this architecture explains why the S800 drives the Franco Serblin Ktemaspeakers so effortlessly.
Operating in Class AB, the Performer S800 delivers 2 × 285 W at 4 Ω and 2 × 185 W at 8 Ω. In bridge mode, a pair can deliver 450 W.
One of the amplifier’s standout features is its bi-amping capability. The S800’s gain is 26 dB; when bi-amping, the second amplifier must have identical gain. A mismatch results in not just level imbalance but also phase shifts and stereo image collapse.
The rear panel includes gain-trim switches for each channel, allowing gain reduction from 26 dB down to 21 dB in 0.5 dB steps. For example, if you’re driving the lower frequencies with the S800 and the upper range with a 300B tube amplifier rated at 24 dB, simply trim the S800 by –2 dB for perfect alignment.
There are also THRU XLR outputs, useful if your preamp cannot feed two amplifiers simultaneously. Additionally, bridge mode can be activated via rear switches.
SPL Performer s 800 Back Panel
Listening Impressions
Since both the Director Mk2 and Performer S800 were demo units, I didn’t need to wait for burn-in. Following Levent Bey’s advice, I used Vovox interconnects and speaker cables. Despite their modest footprint, SPL components occupy very little space on a rack, and front panels can be ordered in red or gray.
High-end components like SPL’s use capacitors that store energy between conductive plates separated by a dielectric material (electrolyte, polypropylene, polyester, mica, etc.). These dielectrics form ionic equilibrium over time; physical movement (such as shipping) can disturb it, temporarily affecting tonal smoothness. That’s why I always let new components rest for 24 hours before critical listening — and did the same here.
To be honest, I initially doubted whether the Performer S800 could properly drive my Franco Serblin Ktemaloudspeakers. Yet from the first notes, the result was stunning — powerful low-end authority, impeccable control across the spectrum, and the kind of composure we associate with high-end solid-state designs. While precision and studio-grade neutrality were clearly present, so was an unexpected musical warmth and emotional depth — never colored, but profoundly engaging.
This extraordinary balance, as described earlier, is the direct outcome of the 120V VOLTAiR high-supply-rail topology.
I performed all listening with the Director Mk2’s internal DAC. The ALPS Mk2 potentiometer ensures silent operation, and the DAC section alone could easily rival or surpass many standalone high-end converters. During testing, I never felt the need to reconnect my Allnic DAC. The presence of a VOLTAiR-based low-pass filter plays a significant role in this result — the defining factor behind the Director Mk2’s sound.
Dire Straits – “Fade to Black” (On Every Street)
This track showcases Mark Knopfler’s signature guitar tone, layered reverbs, and rich bass lines. The left-channel warmth of the guitars contrasts beautifully with the right-channel keyboard ambience. The background is pitch black.
Knopfler’s vocals are centered slightly below ear level and perfectly scaled. The reverberation tails of the background vocals extend naturally — a direct result of the SLP120 filter’s high-headroom linearity. Bass is taut and articulate. SPL conveys both the studio precision and emotional depth of the music effortlessly.
Guns N’ Roses – “Knockin’ On Heaven’s Door”
A theatrical rock rendition of Dylan’s classic, this track demands dynamic breadth. The SPL duo presents its vast soundstage with three-dimensional scale and precision.
Despite heavy distortion layers, clarity never falters. Every pick attack is palpable; the S800’s Class AB stage and high damping factor maintain iron-fisted control. Drive tones remain open and glass-clear. The soundstage is immense.
Stravinsky – “The Firebird Suite: Introduction”
(Reference Recordings, Half-Speed Mastering)
Conducted by Eiji Oue with the Minnesota Orchestra, this analog recording breathes life from silence. Strings bloom from the left, double bass resonates deep to the right, and timpani strikes explode across the room.
The crescendo builds without compression — the stage expands and breathes freely. Even at peak levels, tonal integrity and warmth remain intact.
The 33 dB headroom reserve we discussed earlier manifests audibly here.
Final Thoughts
In Turkey, many still associate SPL with mastering studios, mixing consoles, and measurement tools — and indeed, that’s its origin. But today, the company has carried its professional engineering DNA into the home environment under its aptly named “Professional Fidelity” series.
With products like the Director Mk2, Phonitor XE, and Performer S800, SPL delivers not analytical coldness but studio-grade accuracy infused with tangible musicality. Compared to others in its price class, its performance stands leagues ahead.
With a well-matched loudspeaker (even a difficult one to drive) and a computer as a source via USB, you can enter the world of high-end audio at a remarkably elevated level — without astronomical investment.
The best advice? Book a demo session at BL Müzik, pair the system with a floorstanding loudspeaker, and experience firsthand what the 120V VOLTAiR circuit design truly delivers.