Audio Research Reference 1 preamplifier & VT200 power amplifier

They say you never forget your first time. For me, it was an Audio Research SP-6B that had been heavily modified by Analogique in NYC—which meant, among other things, that yellow capacitors shunted other yellow capacitors all the way up to the top plate. That first taste of the High End—prior to that, you might say my face had been pressed against the window—was definitely love at first listen. That SP-6B was warm yet detailed, and I ended up building a system around it that at least one friend described as a huge musical wet kiss.

I've moved on since then, but I've got to say that I loved that preamp. Not just for the taste of high-end sound it gave me, but also for the insight it gave me into core high-end values. It was reliable—I don't think it ever failed me—and while I changed tubes fairly frequently, that was because I enjoyed tube-rolling. (Tubes were also quite a bit cheaper back then.) The SP-6B was engineered to feel good—I liked the satisfying click of its levers, and the way its knobs felt when I changed volume or source. And, besotted as I was, I thought its silver faceplate and sturdy black handles were strikingly handsome.

That first affair has been on my mind lately. Once again I've been living with Audio Research gear, and some things, it seems, never change. I still think their stuff is ruggedly handsome, even though the Reference 1 and VT200 I've been auditioning have titanium gray faceplates rather than the traditional brushed aluminum. And ARC still makes tube gear so reliable that even tubeophobes can deal with it. But for all of their good, solid family values, this latest generation of Audio Research doesn't sound remotely like their predecessors.

Inside Story: Reference 1 preamplifier
The Ref 1 is built, like the proverbial brick outhouse, and uses an astounding roll call of premium parts. Everything used is absolutely first-rate.

The Reference 1 preamplifier uses eight specially selected Russian 6922s (four per channel) equipped with high-purity plate materials in an all-triode circuit that uses low gain at each stage to produce the best linearity. This high-headroom output circuit is capable of delivering 30V RMS in balanced mode, which keeps distortion low at normal signal levels. The tube heaters employ regulated DC in order to provide isolation from power-line noise.

The multiple isolated power supplies include six regulator stages and two buffers. Three power transformers are used, including two toroids, which provide isolation between audio circuits and digital microprocessor control circuits.

Although the Reference 1 uses differentially balanced input stages as a means of minimizing common-mode noise interference, either single-ended (SE) or balanced signal sources may be used without affecting the preamp's performance. According to ARC, "modest amounts of balanced overall feedback are used for best linearity."

Inside the case, three large circuit boards are arranged in an open layout that keeps audio, power supplies, and the control circuits from interfering with one another. The boards are mounted vertically, which also provides greater cooling benefits. Path lengths are kept as short as possible, and connections from one board to another are by way of heavy-gauge Litz wire. Gold-contact relays are used to route the signal so that the signal paths can be controlled by the microprocessor.

The Ref 1's front panel has four lever switches (Power, Bal/SE, Phase, Mute) and four knobs (controlling Gain/Volume, Balance, Record select, Input select). Each knob is surrounded by LEDs that allow the user to easily confirm level or input functions from across the room. I can't spot the remote sensor on the front panel, but the preamp receives remote signals from just about anywhere in the room.

The controls for volume, balance, and source selection look like conventional pots but are actually two-way, return-to-center switches controlling internal logic. The digital volume control is dual-range: no fewer than eight volume-control sections are used in balanced configuration to guarantee the best linearity and optimum step size.

Graded and matched FETs are used for power-supply regulation and as active current sources to enhance tube linearity. The newest version of the Ref 1 has a removable IEC power cord, a fuse receptacle (3A slow-blow), and the biggest assortment of XLR and RCA connections I've ever seen—two main outs, one record out, and eight inputs—all duplicated in balanced XLR and SE RCA. Yet the back panel isn't cramped; you can connect everything easily, even with knuckles as big as mine.

VT200 power amplifier
The VT200 power amplifier certainly is a big 'un. It weighs 118 lbs, which means you should give careful thought to where you want to put it before you pick that mutha up. I could lift it by myself, thanks to ARC's trademark black metal handles, but I didn't exactly enjoy the experience. Two sets of hands (and two backs!) are far better.

And because the VT200 is fan-cooled, you should also think about placement. Don't just set it down on thick carpeting—place it on a flat surface, or, better yet, an amplifier platform such as the OSAR amp rack I used. Place it as far from your listening position as possible. The fan is pretty quiet at medium speed, which is how the factory supplies it (you can bump it up a notch or slow it down, if you wish), but even with the amp 10' away from my listening chair, I could hear the fan faintly between tracks and CDs. I never found it annoying or intrusive, but your mileage may vary.

The '200 uses eight matched pairs of Svetlana 6550Cs, mounted horizontally along the amp's sides, in Audio Research's proprietary version of the ultralinear circuit. This uses partial cathode coupling, which, ARC claims, imparts triode qualities while providing higher efficiency than triode circuits. The cathodes of the output tubes are DC-coupled to the speakers; the plates and screens are coupled through wide-band output transformers with special low-loss dielectric insulation. Regulated DC drives the heaters on the input tubes: specially selected Russian 6922s using high-purity plate materials. (The driver tubes are also Russian 6922s.) Tracking-bias circuits maintain constant current in the output tubes. FET circuits regulate current for the input stages, and trimpots allow for user adjustment of each channel's AC and DC balance.

The VT200 has massive dual-mono power supplies, with high energy storage and choke filtering for each channel. Separate windings on the transformer are used for each channel. Bidirectional diode coupling is used to share the load between the dual-mono supplies during high-demand conditions.

The power-supply filtering employs Decoupled Electrolytic Capacitor (DEC) circuits to minimize any sonically undesirable qualities of electrolytic caps. ARC also employs elaborate "step-down" filters that use multiple film bypass capacitors of progressively smaller values.

Like the Reference 1, the build and parts qualities of the VT200 are impeccable: its tube sockets have heavy, full-contact, gold-plated pin sleeves; extra-heavy copper plating is used on the circuit boards; the point-to-point wiring uses OFC and Litz wire; vibration-damping pads are used within the chassis; multiple damping rings are fitted to the input tubes; and even the InfiniCaps used have proprietary ARC terminations.

On the rear panel are 14 high-quality, brass, "nontwisting" speaker connectors: two center/ground taps for unbalanced operation and three pairs for each channel for 1 ohm, 2 ohm, and 4 ohm, unbalanced operation and 4 ohm, 8 ohm, and 16 ohm balanced operation. There are both single-ended RCA and balanced XLR input connections (pin 3 of the XLR jack has to be shorted to pin 1 to use the unbalanced inputs). There is an output fuse (10A slow-blow) receptacle in the center, directly above the fixed, 14-gauge power cord. The front panel sports only a heavy-duty rocker-style power switch and a green LED power indicator.

Can two walk together, except they be agreed?
Some companies can survive in the marketplace for a long time and still revel in their funkiness—MG and Triumph come to mind. (But I guess they didn't make it into the '90s now, did they?) Audio Research isn't one of them. They make gear that just flat-out works, with nary a burble, a flutter, or a pop to be experienced. The digital volume, balance, and source-selector controls on the Reference 1 were just as sure and reliable as any manual control I've ever used. I put the gear through some all-day-long listening sessions—some of them in the middle of Northern New Mexico's monsoon season, complete with daily thunderstorms—and it never stumbled, even when the electricity was obviously fluctuating erratically. If you've always wanted to try tubes but were afraid they required too much maintenance, this is the sort of tube gear you can comfortably live with.

On the other hand, if you like to think of tube gear as capricious distortion generators, then you might want to stay away from the Ref 1 and VT200—they'll challenge your assumptions about the nature of tube amplification. Simply put, these two components have no trace of "tube sound," as the term is commonly used: warm'n'fuzzy these babies definitely are not.

Audio Research
5740 Green Circle Drive
Minnetonka, MN 55343-4424
(612) 939-0600