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Reviewer: Mike Malinowski
Source: Walker Black Diamond turntable; Walker Reference phono preamp; Clearaudio Goldfinger
Preamp: VTL TL-7.5 Reference; darTZeel NHB 18NS
Amp: darTZeel NHB-108; VTL S400
Speakers: Wilson X-2 Alexandria
Cables: Transparent Opus, Silent Source, Omega Mikro Ebony speaker cables; Transparent XL w/MM interconnect to amp; Silent Source and Xtreme between phono pre and preamp
Stands: Michael Green racks, VPI phono stand, Zoethecus, Walker Prologue Amp Stand
Powerline conditioning: Furman Balanced Power, Walker Audio Velocitor S, PS Audio 300
Sundry accessories: Walker Audio Valid Points resonance control discs; ASC tube traps; Echo Buster absorbent and diffuser panels; Argent Room Lens; separate 90-amp sub panel feeding five dedicated cryo'd outlets; Loricraft Model 4 record cleaner; Walker Talisman
Room size: 22' x 17' x 8' (double sheetrock on 2"x 6" framing in basement)
Review component retail: $16,500; upgrade from Series I to II $4,500
Originally the Clark Kent of audio companies, VTL offered good sound and solid value with components specializing in the meaty part of the bell curve. Yes, they offered entry-level preamps and certainly the mighty Wotan set benchmarks for tube-based power and control. However, when you thought 'reference products', you more likely would name Audio Research or Conrad Johnson. That was then. Today things have changed at VTL. Yes, tubes are still at the heart of all their products as one thing that's unchanged. The tube gene is apparently deeply embedded in the Manley DNA, spanning multiple generations and now three different companies.

The company was founded by David Manley, Luke's father. An excerpt from the VTL company history describes the beginning: "Originally VTL was founded upon designs that are based on recording studio prototype playback amplifiers. The forerunners to the first VTL products were originally designed in 1980 in South Africa by recording and film engineer David Manley, where the recording studio environment gave the VTL designs their heritage for sonic quality and reliability under long and arduous working conditions. Professional production for amplifiers designed for home audio use was started in Britain in 1983 to service distribution in Europe...

"...When it became obvious to both Luke and David that the company needed a full-function manufacturing facility, they decided to relocate production to Southern California, to take advantage of the readily available supply of electronics and manufacturing vendors and the labor force that was servicing the defense electronics industry in the Los Angeles basin. In 1987 the factory was moved to its present location in Chino, CA -- where all VTL products are made for worldwide consumption, and the same location that VTL occupies now."

Producing primarily a line of dynamic, extended and fairly priced power amplifiers, the VTL family sound was not 'tubey' or overtly romantic and they developed a solid market presence. Unfortunately -- or fortunately depending upon your perspective -- David and Luke suffered irreconcilable differences about how to run the company going forward. David wanted to take the company into a more pro-line of products with guitar amplifiers and recording kit; Luke wanted to focus on high-end home audio. They ultimately split the company right down the middle - VTL went to Luke and Manley Labs to his father. Today Luke and his wife Bea own VTL; David's ex-wife EveAnna owns and runs Manley labs; and David owns David Manley Design Ltd. of Paris.

After the split, Luke determined that one key to success was to develop a sound and stable dealer network. He chose not to go head-to-head with Audio Research dealers, which would have only forced them to either offer tube amplifier A or B to their customers. "We targeted high-end dealers, many of whom sold Levinson equipment, giving music lovers a reliable tube-based alternative to solid-state." The 7.5 represented not so much an evolution from the original colorfully named preamps such as the Super Deluxe and Ultimate but more of a revolution, a totally clean sheet design and an all-out assault.

The company metamorphosed and began to don its Superman cape with the development of the Siegfried amps and 7.5 preamp. VTL still produces solid, excellent sounding, reasonably priced equipment using the lessons learned from their Reference series, effectively trickling them down to other products. As with many great ideas, mix in equal parts of vision, timing, a little luck, hard work and presto, you can have an overnight success on your hands.
Prior to the launch of the 7.5, Siegfried monos and S-400s, VTL was known primarily for quality high-powered, reasonably priced tube amplifiers. Although their preamps sold well, they mostly flew below the radar in the preamp market. The 5.5 received very good reviews but really did not crack the market until the introduction of the 7.5. Some of the design and functionality can be traced back to the Mark Levinson Reference 32 preamp, one of the originators of the two-box reference preamp design that incorporated processor logic and control. The Levinson Ref 32 hit the market with a splash; its functionality set the benchmark for usability and flexibility. It did everything except slice and dice your lunch. If you included its optional phono module, you could even adjust cartridge loading and capacitance from the comfort of your listening chair by remote control. Sonically, many believed it to be at the pinnacle of solid-state preamplifiers for its time. Closely following the success of the Levinson and carefully listening to dealers, Manley set out to produce his own version of the two-box reference but with some critical differences. His was to be a hybrid design with a very simple, single-stage tube amplifying circuit using a proprietary MOSFET output buffer. It was to take the flexibility of the Levinson and raise the sonic stakes using tubes. Those who demanded a two-boxed reference system now had a tube-based option.

The 7.5 represents VTL's all-out assault on the state-of-the-art, not built to a price point but to be the best the VTL design team could deliver. One step down from the Reference is the VTL Signature line, which distills the sound and the majority of the circuitry into one-box units at a competitive price. The 7.5 is Reference status, the 6.5 Signature status just as the S-400 in the sonic family is slightly the junior of the reference Siegfried amplifiers - assuming that you call a 220 pound power amplifier with 16 tubes a junior anything.

The two-box design is the classic clean box/dirty box approach. The control box contains the switching, processors and power supply while the audio chassis contains the amplification plus additional filtration. Neither digital components nor digital signals reside anywhere in the amplification box and at 70 pounds, it weighs more than your average amplifier.

The control chassis front panel is simple, clean and elegant. Six buttons select the inputs with indicator lights for each: green for single-ended inputs and blue if the input is configured for balanced. Two tape inputs, a monitor switch, phase, balance and mute complete the push button selection. An LED display window is dominated by a circular flush-mounted volume control which performs several functions. The Control Chassis' rear panel provides a center-mounted power umbilical for the clean regulated power supplies to the various stages of the amplifier section, two 50-pin SCSI connectors for control signals, four 12V trigger outputs, master on/off and A/C power receptacle.

The front of the audio section is simple and clean with only the VTL logo and a power LED indicator. Contrasting the front, the connections on the rear panel indicate the 7.5's flexibility - control SCSI cable inputs, Power Link from the control box plus a full array of balance and single-ended inputs/outputs, including two primary outputs for bi-amping. A pair of tape inputs and buffered outputs complete the rear. In all and with 39 various connections, the 7.5 provides more than adequate control for any audio system.

Visually, the system has an understated elegance, available in silver or black, and will certainly complement most audio systems.

Throughout the review process, I reference the Levinson Reference 32 and darTZeel NS18 for comparison - the Levinson for its design and features and the darT for its resolution, purity and overall sonics. While the 32 was a benchmark product and certainly set the standard for flexibility, today the 7.5 easily eclipses the Levinson musically. The Levinson 32 was my reference preamp for five years and the immediate predecessor to my 7.5 Series I. The darTZeel was in my system recently and was directly compared to the 7.5 Series I, so hopefully the comparisons will be meaningful.

While I could be happy with the functionality of either the VTL or Levinson, they go about their missions somewhat differently. The VTL uses precision regulated power supplies while the Levinson regenerates the AC from 60Hz to 400Hz and regulates that to DC. The control methods are equally divergent. The Levinson uses processors in the audio section that are always 'sleeping' during playback. Let's say you want to change the volume. The control unit sends a digital signal to the processor and it wakes up. The volume change is carried out by the processor and it then reverts to sleep mode. The only time a noisy digital signal is transmitted is during that fraction of a second when an action is required. On the other hand, Luke and his engineering group wanted absolutely no digital processing in the amplifying section, period. That's where the massive pair of 50-pin SCSI cables comes in. Seeing a Centronics SCSI connector might imply digital communication between the control center and amplifying sections. Not. Although born in the PC and digital environment, their only purpose here is to deliver 5V DC control signals for opening and closing the volume, balance, offset and input selections via sealed relays located in the amplifier section. With this clean box/dirty box design, power supply and control functions are kept completely separated from the audio signal.

Four inputs can be configured to balanced or single-ended, two inputs for single-ended only. Then there are two single-ended tape inputs plus a tape monitor function for both tape loops, four separately programmable trigger output and a processor loop where any of eight inputs can be assigned as fixed unity gain pass-through. Whew! There's enough switching flexibility to bring a smile to the face of even the most ardent twiddler and fiddler.

Sonic bottlenecks
The design team focused on overcoming a series of what Luke calls 'sonic bottlenecks' believed endemic to most preamps. "A major design goal for the VTL 7.5 was to sonically outperform any existing preamplifier design using measurements to back up empirical findings." The four-year challenge of the VTL technical group was to design a reference grade, fully differential tube-based circuit with a very high common mode rejection ratio. My layman understanding of the differential circuit is one that amplifies the voltage of the musical signal while rejecting the voltage differential - noise and electrical grunge flowing into and between various components in your system via the ground and/or shield connections. How well that the differential circuit reduces this common mode noise is measured in a ratio called the Common Mode Rejection Ratio (CMRR) and apparently somewhat difficult to implement perfectly in the real world using tubes. The circuit requires very precise parts matching in order for the error correction to be effective.

The design team wanted a component "that would be totally unaffected by outside environmental influences ... Sonic performance should be usable, predictable and consistent regardless of AC condition, load, source components, physical vibration or digital and other external radiated noise." The result is a preamplifier "capable of driving any load with any length of cable." These goals required the development of a new type of push-pull, low impedance, high-current output stage.

I'm fascinated by the design process, often non-linear with interesting twist and turns. Science historian James Burke wrote and narrated an excellent BBC television show, Connections, which postulated that modern world events and technologies stem from a series of seemingly unrelated but yet highly interconnected events. For example, follow his connection from Calamine (yes, as in Calamine Lotion for poison ivy) to Pyroelectricity to the Theory of Relativity and finally to the Atomic Bomb - it's a fascinating journey. Although not quite as profound, the path to the top in audio design and its version of 'connections' is still interesting nonetheless. Back in 1993, no one at VTL said, "let's build a reference hybrid preamp." It was a meandering path, beginning with a genetic family disposition towards tube design, a fraternal divorce, a company split and finally the introduction and failure of multi-channel high end audio. Actually multi-channel played a significant role with Luke and his group dipping their collective toes into a prototype six-channel preamp not designed for Home Theatre but for audio such as DVD-A or SACD.

"It was a really interesting evolutionary leap for us. When DVD audio came out, there were six analog outputs on the DVD player. It was a very interesting concept because you could do things in surround that were very difficult to do with traditional two channel stereo such as delaying the bass through the room and the ability to make a room sound much bigger than it actually is - trying to get towards a live listening space. VTL had an interest in surround music but not necessarily home theater. We actually built a six-channel preamp when DVD audio came out and it was great. Tubes actually shine in this environment because they can handle the dynamics well, really powerful and clean. But ultimately I was disappointed with surround music. As soon as people heard instruments in the rear, they started laughing at the cheesy effects, bringing back all the bad things about quadraphonics. It was like, are we back in the 60s or what? The challenge with that six-channel preamp (we actually called it the 2.5.1), was whether we could fit 12 tubes into one box. This is a long way around to the hybrid discussion but it made me start to think about what tubes were doing for us. And what were they not doing for us. And what were they best at?"

After determining that it was not headed for production, VTL used the prototype to simulate three stereo preamps as a test bed for the new VTL Reference designs. Luke's new vision required redefining the role of tubes. Amplifying? Buffering? Rectifying? Tubes have their strengths and weaknesses and Luke sought to answer what role they would play in the new direction he was taking VTL. But no matter what the direction, the solution always returned to simplicity of design especially in the amplifying stage. Mix in Luke's passionate belief that every element, switch and contact in the signal path degrades the sound and you have the fundamental tenants for the 7.5.

Despite its mammoth size and weight, I am amazed by the utter minimalism of the audio circuit. Just one 12AU7 per channel (replacing the 12AX7 in the original Series I) is the entire tube complement mounted on a springy, shock-absorbing 3" by 3" circuit board. Although VTL claims innovations in the 12AU7 amplifying circuit, the real design challenge for the new 7.5 was the output buffer.