VTL TL-7.5 Reference Line Preamplifier
Review By Wayne Donnelly
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  On first seeing the production VTL TL-7.5, I remember thinking that this impressively weighty, extremely full-featured, handsome two-chassis preamplifier would be a good choice to illustrate the phrase “statement product” in that big high-end audio glossary in the sky. Although far from the costliest preamplifier available, the $12,500 7.5 is clearly an ambitiously conceived big-ticket component, and it looks every inch the part.

I had encountered various iterations of the 7.5 over the five years it was in development. Luke Manley and Beatrice Lam (Mr. & Mrs. VTL) commute most weekends from the Southern California VTL factory to their Bay Area home, a 15-minute drive from me. Luke stops by occasionally when my VTL amplifiers need some TLC. At the beginning of the 7.5 project Luke told me that one of his goals was to beat my longtime reference Thor TA-1000 line stage, which he found quite impressive. Thereafter, he would occasionally bring over his working prototype 7.5 to compare to the Thor. Early on, the 7.5 didn’t quite measure up, although the prototype sounded better each time. But at the last such visit, shortly before the 7.5 was formally unveiled at the 2002 CES show, the tide was turning in favor of the VTL. I’ll comment below on the recent comparison between the two.

First Impressions
My first impression of the 7.5 was formed while watching the UPS driver start to hoist the two shipping cartons at once, then quickly set them down and bring out his two-wheeler.  After unpacking the two cartons I was even more impressed.  These things are heavy — about 70 lbs altogether.  I have wrangled 200+ watt amplifiers that were less substantial than either the power supply/control or audio circuit chassis of the 7.5!

But weight is only the beginning. The industrial design of this preamplifier is elegant.  The subtly sculpted fascia of the audio unit   displays only the VTL logo and a small power LED.  The control unit is a fine example of aesthetic simplicity concealing functional complexity: a single row of discreetly labeled input pushbuttons, each with an LED indicator; on the far right a black display window containing the numeric volume level/channel balance indicator, a flush-mounted manual volume control with a finger indent (way cool!), and three red LEDs to indicate activation of the phase reversal, channel balance and mute functions.

The rear panel of the control unit has only three connections: one for the large center umbilical that carries pure DC current, and SCSI connectors for each channel, which transfer control commands that activate the switching relays in the audio chassis.

The rear panel of the audio chassis is initially daunting — in addition to the power and control interface connectors, there are (starting from the bottom) a row of XLR connectors and then a row of RCA jacks for six inputs and two main outputs.  Above them is another row of RCA jacks for the tape monitor and processor circuits.  So logical and well marked is the mirror-image layout that one quickly grasps it, and after a short time I found that I could easily connect and disconnect other components simply by counting over to the proper jack — a real benefit as there is no room to go behind my equipment rack, and the massive audio chassis is not easy to move around on the shelf.

It is worth noting that the XLR and RCA inputs may be simultaneously connected to different sources.  To switch from one to the other one need only press and hold briefly the corresponding front-panel button; the LED will switch from green (RCA) to blue (XLR) or vice versa.  These inputs are so well buffered that I was never able to hear any leak-through when so configuring them.

Technical Design Highlights
As its name suggests, VTL (Vacuum Tube Logic) has heretofore been devoted exclusively to glowing glass. VTL products have proudly carried the “Pure Tube” badge.  But this, VTL’s flagship preamplifier, is a hybrid design with tube input and solid-state output.  When I asked Luke Manley about this, his answer was that performance was more important than ideology, and that the hybrid design was necessary in order to achieve all of the design goals of the TL-7.5.  It works for me — the proof is in the listening.

The TL 7.5 is as thoroughly conceived and meticulously engineered and built as any audio component I have seen and heard. The following highlights taken from the VTL Web site are far from comprehensive, but will give the reader some idea of the depth of Luke Manley’s vision for his ultimate line preamplifier. I have added comments on the relevance to audiophiles of these features.

Tube complement: two 12AX7 tubes. The 7.5 is purposely voiced with moderately priced and widely available input tubes—in this case Svetlanas. I suspect that tube rolling is likely to prove superfluous, and might well throw off the preamplifier’s flawless tonal balance.

Fully differential circuit, balanced inputs and outputs; mirror-image layout. This brilliantly executed differential architecture does sound better in balanced mode than in single-ended—especially after I upgraded my VTL MB-750 Reference monoblocks with the “Super Balanced” input stage VTL developed for the new $40,000/pair, 800-watt Siegfried  Reference amplifiers. For this writer, the mirror-imaged rear panel layout facilitates connection and disconnection by feel, compensating somewhat for my impaired vision.

Isolated Control Unit chassis with 12 separate fully regulated power supplies. This and numerous other no-compromise design decisions account in large part for the hefty price of the TL-7.5.

Separate Audio Unit chassis with zero internal digital activity. This rigorous “clean box/dirty box” architecture strikes this writer as so intuitively desirable that I wonder why it is not widely used in flagship reference-level components.

Low-noise processor control design for all functions. See previous bullet.

Simple circuit topology with low negative feedback for musical purity. Also characteristic of VTL amplifier designs. In my view, a significant factor in the company’s characteristically open, airy upper frequencies.

Logical sequenced soft-start power-up for extended tube life. The 7.5’s 90-second stabilization interval also allows ample time for most any tube amplifier to stabilize, avoiding nasty power-up noises. I also appreciate that the preamplifier volume level is always at zero when the 7.5 becomes operational. No rude surprises from last night’s party!

Ultra-low-impedance output stage to drive any length of cable and any power amplifier. This highly desirable robust output capability is also characteristic of the lower-priced VTL preamplifiers.

Shock-mounted gain stage. This and the next point exemplify the premium placed on optimum audio performance, and of Luke Manley’s refusal to cut corners with his Reference preamplifier.

Modular volume control and output stages. If something notably better comes along, the architecture can accommodate it.

95-step 70dB discrete relay attenuator for all attenuation functions. This control allows for very precise incremental adjustments. One idiosyncrasy is the faint ttcking heard as the relays operate during volume changes. Since I can’t read the numeric volume display from my listening seat, the ticks give me a sense of how far up or down I have gone.

Processor loop – any of 8 inputs can be assigned as fixed unity gain pass-through. The 7.5 provides for exceptional configuration flexibility, especially useful for complex home theater or multi-purpose setups.

Four separately programmable trigger outputs. I have not used this feature, but again it could be very convenient in a multi-component home theater system.

Programmable input offsets. In a system with multiple sources, this feature allows the user to match precisely the playback levels of all the components, so that the volume level remains consistent when switching from one source to another. This capability offers a nice civilizing touch, and it is a godsend to a reviewer comparing, for example, CD players or DACs, SACD vs. Red Book CD, or vinyl vs. digital software of a specific recording.

Rear IR receiver for all functions. In my setup, remote functionality is consistently easy, with the IR receiver having an effectively broad angle of acceptance.

Rigid combination steel and non-magnetic chassis and machined aluminum remote wand. I have not seen better fit ‘n finish than that of the 7.5 and its ergonomically superb remote wand.

Review Setup, Ergonomics
This review is based primarily on putting the 7.5 into the reference system described elsewhere on Enjoy the Music.com™ in place of my long-term reference Thor TA-1000. A number of source components and other amplifiers, either already reviewed or scheduled for future review, were also auditioned with the 7.5.  A variety of music from medieval to the blues, on CD, SACD and vinyl, were brought to life by this marvelous preamplifier.

Although programming some of the configuration options may be slightly complicated--judging from the lengthy but well organized and clearly written 7.5 owner’s manual — the user interface for the music listener is delightfully simple. After starting a CD or LP, everything a listener needs is right there on the remote control: volume, balance, phase (or polarity, if you will), mute and even a fade control that lets you drop playback volume to, for instance, answer the phone, and then restore it precisely to the original level.  The layout of the remote wand is simple, and easy to use even in the dark.  The wand’s rounded bottom edge fits pleasingly in the hand, and it feels sufficiently solid and weighty to do double duty as a bludgeon should hand-to-hand combat suddenly erupt.

If you are sensitive to correct electrical phase, you know that there is very little phase consistency among recorded sources. That being the case, the ability to switch between 0 and 180 degrees from the listening position is especially valuable. When playing CDs, phase differences are more apparent in the digital domain, so I leave the manual phase flip button on the Dodson DA-218 DAC set on reverse.  That way I can switch back and forth remotely and easily hear which setting sounds better. And since I listen to lots of vinyl, having the phase flip on the preamplifier remote allows me to also find correct phase for the LPs. I continue to be puzzled by the omission of this control by countless high-end audio manufacturers.   Bravo VTL!

Listening to the TL-7.5
I’m not going to start gushing about stunning sonic revelations--scads of previously unheard inner detail, vastly improved extension, dynamics, air, etc. etc. After all, it’s not as if I’ve been listening to audio “ chopped liver” until now! The Thor TA-1000 has stood up against quite a few superb preamplifiers for seven years — virtually an epoch in the fickle world of high-end audio reviewers.  Having been upgraded a few months ago to Mk. II status, it sounds better than ever, and now features remote volume control. None of the excellent  (but admittedly less expensive) preamplifiers scheduled for future review can match it.

But on the whole, a point here, a point there, the 7.5 emerged as the winner. Where were the main differences?

Differentiation: the Thor is very slightly more forgiving of lesser-quality recordings, which from the standpoint of pure listening pleasure can be a good thing. The 7.5 more clearly delineates shortcomings in all genres of software, although it never comes across as “ruthlessly revealing”… just honest. 

Quietness: the 7.5 is simply the quietest preamplifier I have ever used. Especially when playing a great CD through the Dodson DAC and the 7.5, the sonic background is a deeper and more profoundly black than with any other combination I have heard, and that degree of quietness does allow some previously unperceived spatial and musical detail to be heard.  Moreover, the 7.5 is, in my environment at least, impervious to external annoyances such as EMF/RFI noise corruption.

The usual suspects: after listening week after week through the 7.5, it is clear that frequency extension at both ends of the spectrum, macro and micro dynamics, openness and air, spatial resolution and imaging precision are, easily and without exaggeration, simply right.

Every audiophile knows the old saw that the perfect preamplifier would be “a straight wire with gain.“ But the more I listen to every kind of music through the 7.5, the more it seems to me like “no wire with gain.“ This extraordinary component imposes less sound of its own on music than anything else I have heard.

A few years back I had the privilege of reviewing the CTC Blowtorch preamplifier, with circuit design by John Curl, superb board layouts by Carl Thomas and meticulous parts selection and voicing by Bob Crump. (This same team created the Parasound Halo JC 1 monoblock amplifier I named as an award winner in the January Enjoy the Music.com Review Magazine.)

The qualities that for me had set the Blowtorch apart from all other preamplifiers were very much like those I ascribe here to the 7.5. Returning it--most reluctantly--to John Curl after the review was complete was the only time I was (slightly) unhappy to reconnect my esteemed Thor. Had I had the funds, I would have ordered a Blowtorch right then.

There is no Blowtorch/7.5 shootout in the offing. The Blowtorch is built to order, so there aren’t many lying around, and their owners are understandably not inclined to loan them to reviewers. So, given the interval between listening to the two, I don’t know which is “better.” But I do believe the 7.5 is at least on a similarly exalted level, and I’ve never felt that way about any other preamplifier.

Summing Up
If this all comes across as an immoderate rave, I suppose I must plead guilty.  Try as I might, I just haven’t found anything to complain about to counterbalance the 7.5’s cornucopia of sonic and ergonomic virtues. Would I like a simpler version, with fewer inputs and features, at a lower cost? Absolutely.  Perhaps if we close our eyes and wish very hard, that dream will come true someday.  The 7.5 has far more connectivity than I will ever use — but I am unable to perceive any trade-off in musical quality that can be related to this unusually flexible architecture or to the well-thought-out user interface features that make it such a pleasure to use. My advice? Don’t buy any high-priced preamplifier without carefully listening to the VTL TL-7.5. it is now my new reference preamplifier.

Specifications
Vacuum Tube Complement: a pair of 12AX7

Inputs: Four pairs balanced/XLR or RCA single-ended
            Four pairs single-ended/RCA

Outputs: two pairs balanced out
               two pairs single-ended RCA out 
               two pairs single-ended RCA buffered Tape Out

Remote Control Functions: Power, Source Select, Volume up/down, Mute, Fade, Balance Control, Phase Reverse

Gain: 20dB

Output Impedance: 25 Ohms (Max 150 ohms at 10Hz)

Input Impedance : 50K Ohms (20k ohms min)

Frequency Response: 20Hz to 100kHz 

Maximum Output Voltage: 45 Volts

Channel Separation: > 100 dB @ 1KHz

Channel To Channel Cross-Talk: >100dB

Power Consumption: 150 Watts

Dimensions (W x D H): Control chassis
                                        17.5 x 17.5 x 4 inches
                                        Audio chassis
                                       17.5 x 17.5 x 6 inches

Weight: 75 lbs.

Price: $12,500

Warranty: 5 years parts and labor with return of owner registration card; tubes 6 months

Company Information
Company Information:
Vacuum Tube Logic, Inc.
4774 Murietta Street, Suite 10
Chino, CA 91710

Tel: (909) 627-5944
Fax: (909) 627-6988 
Website: www.vtl.com