The optional, built-in phonostage (my review unit came phono-equipped) is zero-feedback, capable of both mm and mc operation with variable loading. Moving-coil loads are 470, 300, 250, 200, 150, and 100 ohms, while moving-magnet loads are 100x those. The mm phono is fitted with six 12AX7 triodes and is capable of 44dB gain. In mc mode, two wide-bandwidth transformers (sourced from Lundahl) get switched into the circuit, adding 20dB of gain passively.
I’ve been on a preamp quest for a while now, and, in my limited experience, what I’ve found is, features and superior technology aside, tubed preamps are basically designed to create weight and drive or else to have finesse and sophistication. If you look at their spec sheets, you’ll see gain levels that cluster either around 12dB or 20dB and this, generally, tells you what the preamp emphasizes. A gain around the lower figure would lead you to expect finesse über alles. Gain nearer the higher figure suggests tone and drive as foremost. VAC has made preamps in both categories (the Signature I even exceeded the “big on drive” category with a gain of 35dB!) and, given its 12dB gain spec, one might assume the Signature IIa to fall on the finesse side of the fence. And, at first, I thought so too, as, paired with my reference deHavilland KE50A mono amps (40Wpc), it did seem the Signature IIa had all the sophistication of my deHavilland Mercury 3 linestage—lovely with a gentle hand on orchestral music, able to resolve evanescent details and create a subtle, organic flow. But it also somehow sounded “light” to my ear, missing body on strings and sometimes voices, and so I ventured onward, pairing the VAC preamp with power amps that had more output and quickly discovered its strength, tonal weight, speed, serious authority, and ability to throw a big soundstage. The Signature IIa seemed to split the difference between my ad hoc tribes of preamps—or did it just combine the best traits of both?
Physically, the Signature IIa is one of the loveliest mechanical things I’ve ever seen. Though my review unit came in black (silver also available), that hardly begins to describe the illusion of depth in the glossy 10mm-thick faceplates of both the control and power units, glittering with gold metallic flakes embedded just under the layered lacquer finish. What’s more, both have as centerpiece an inset, backlit LED logo with the VAC trademark—an encircled lightning bolt beside capital letters spelling out “VAC.” Running underneath the logos are lines of understated gold script silkscreened on, identifying each. The bling-factor on the control unit is pretty high too, as there are two large, rakishly beveled, hand-sized gold knobs marked Volume and Selector, and four smaller outlying ones marked Monitor and Mute on the left, Cinema (for bypass) and Power on the right. Build-quality is superb and each aluminum chassis is finished with an even, flat-black powdercoat.
Around back, the preamp absolutely bristles with connectors. These are premium Cardas rhodium types that can stand up to a lot of cable swapping. There are four sets of main outputs, two RCA and two XLR; five line inputs, two with both RCA and XLR jacks; a set of RCA Cine inputs; a tape loop; a control knob for phono loading (if phono is fitted); and a set of mc phono inputs on RCA jacks (converts to a sixth line input if phono is not fitted); a selector knob for mm/mc; and a set of mm phono inputs (RCA). Below these connectors are switches for SE/BAL selection and for adjusting brightness or dimming of the logo. Because the Sig IIa has four sets of main outputs, you can readily bi-amp, either single-ended or balanced.
With the VAC Signature IIa, I used four different amps, two sets of speakers, and both balanced and RCA interconnects. For sources, I used analog, CD, and an iMac with a USB DAC. After an initial run-in period of scarcely 50 hours, the preamp distinguished itself in multiple and (I’d previously thought) contradictory areas—finesse, tonal weight, and drive. This preamp created musical momentum in ways that were both powerful and subtle. Add to this, the Signature IIa also demonstrated fine spectral balance and superb dynamic and timbral contrasts. In its performance, it transcended both gross categories of preamp I’d presumed existed. As I mentioned already, though it did not match perfectly with my moderate-power deHavilland KE50A tubed monos, the Signature IIa sounded great with three other amps—a VAC Phi-200 (100Wpc), Herron M1 solid-state monoblocks (150Wpc), and a VAC PA-100/100 (100Wpc). Compared to my reference combo of deHavilland KE50A tube monoblocks and Lamm LL2.1 linestage, the Signature IIa with Herron or VAC amps consistently sounded more polished, with better imaging and a wider and taller soundstage, reaching up to a yard on either side of the speakers and almost as high above them. Believe it or not, the Signature IIa sounded pretty much the same run balanced with Cardas Clear balanced interconnects or run single-ended with Siltech 330i or Cardas Clear unbalanced. As for speakers, both my reference Von Schweikert VR5 HSEs and a review pair of Von Schweikert VR-44s that arrived late in the review period worked terrifically well, with the powered subwoofers of the VR-44s providing more bass presence, detail, and slam. The remote operated smoothly during the entire review period.