Tube Preamp Reviews

I had a wonderful audio moment the other night. It was late in the evening, after a long day. I was standing in the middle of my makeshift listening room—Trish's dining room—and in spite of the fact that we were moving in just a few weeks, I'd just unpacked and set up my combo of VPI TNT Mk.V-HR turntable and tonearm with Grado Statement cartridge and dug a box of LPs out of the stacks in the garage. I cued up Dave Brubeck's Time Out (Columbia/Classic CS 8192), and the first notes of "Blue Rondo à la Turk" froze me in my tracks.

The music hadn't just started, it had come to life. I sat down, mesmerized, and the stress and pressures of the day melted away, replaced with feelings and emotions from other times and places. There was a tinge of the electric excitement that permeates the air before a concert, when the lights dim and the performers take the stage. There was also the simple joy of being swept away by music. But most of what I was feeling, I think, was a lightness and happiness that reminded me of discovering music and audio in college and grad school, a joy that, in the recent frantic weeks and months of swirling logistics, merging families, moving, and endless business travel, had somehow gotten lost.

Aromatherapy is based on the premise that a profound, direct connection exists between the olfactory receptors and the brain—how the smell of new-mown grass, for example, can make us feel the way we did as a child. I occasionally experience the same sort of thing based on my hearing. Sounds—often music, but not always—can take me back to other times and places. Not just remind me of them, but actually re-create the feelings I had. As I've traveled through the world of high-end audio, I've often found that inserting into my system a new, profoundly better component, one that raises the system's performance to a higher plateau, can re-establish this connection, or make it noticeably more direct. In this case, the source was easily identified: the Valve Amplification Company's Renaissance Signature Mk.II preamplifier.

A Renaissance preamp at last!
The Renaissance Signature was released in 2000 after six years of development by designer Kevin Hayes. At $17,000 ($13,000 without phono stage), it was VAC's top model, and the first VAC preamp to bear the "Renaissance" name. Now, the Signature has been extensively updated and become the "Mk.II." The most notable changes between the original Signature and the Mk.II are the use of both input and output coupling transformers in the line stage, and the deletion of the pair of 12AX7 tubes from the line stage, leaving only a pair of 8417 dual-triodes as a differential gain stage, and a pair of 12AU7s as the buffer circuit for the tape output.

The bulk of the design elements that made the original Signature so special remain in place. There are no coupling capacitors in the signal path and no loop negative feedback. The gain stage is fully differential, and consists of direct-heated triodes. On the input side, the Input Selector switch both selects the source and sets the grounding for balanced or unbalanced sources, the latter converted to a differential configuration at the input transformer.

Both balanced (XLR) and unbalanced (RCA) outputs are provided, with a rear-panel selector switch selecting between the two and, again, establishing the appropriate grounding configuration. The output transformer not only converts the differential signal to unbalanced if necessary, but also allows the Signature Mk.II to drive virtually any combination of cable and amplifier inputs. In fact, the VAC's current capabilities are said to rival those of many small class-A1 power amplifiers.

The VAC's phono stage is an unusual configuration, and struck me as a throwback to an earlier time. Through the MM (moving-magnet) inputs, it provides 44dB of gain via a single, fully differential gain stage, implemented via six 12AX7 dual-triode tubes. Through the MC (moving-coil) inputs—and when that rear-panel switch is flipped—rather than increase the gain actively, the switch inserts a pair of wide-bandwidth transformers into the circuit to achieve an additional 20dB of gain. In either case, it uses passive equalization. I did the bulk of my listening using either a Grado Statement or a Benz Micro L04 cartridge, and the MC inputs provided the best mix of detail, depth, texture, and dynamics.