Tube Preamp Reviews

Following the introduction of their very expensive, tube/FET hybrid SP11 preamplifier, there were rumors that Audio Research was working on a hybrid tube/transistor preamplifier targeted to cost less than $2000. The rumors were confirmed when ARC showed a black-and-white photo of the SP9 at the 1987 Winter CES. Obviously, like all magazines, we were impatient to receive a review sample, but the first review of the SP9 actually appeared in the summer '87 issue of Peter Moncrieff's IAR Hotline. Peter's review was almost intemperately enthusiastic, comparing the SP9 positively with early samples of the SP11 and suggesting that its sound quality was considerably better than would be expected from its $1695 asking price. Naturally, we were anticipating good things when our review sample arrived in Santa Fe in late July.

For those who frequent the audio discussion groups on the Internet, the method by which Stereophile selects products for review seems to be a continuing source of fascination and conjecture. Supporters of fledgling manufacturers—whose products these Webcrawlers just happen to own—rail against the rule that products to be reviewed in the magazine must have at least five US dealers. Some suggest that Stereophile's selection of review products is all about catering to advertisers and friends in the industry, a process that seems intended to exclude their favorite products from consideration.

We audio writers have our niches. Mikey loves analog, Artie likes to play with horn speakers and assorted oddball British kit, and I really enjoy reviewing affordable speakers. There's something exciting about hearing the fruits of the labors of a creative designer who's applied his talents to meet a stringent price point and created a speaker that can entice into our hobby the financially challenged music lover.

In red letters on the first page of Chinese audio manufacturer Audio-GD's website are these words: Wisdom in mind, enthusiasm at heart.

I like this goodwill greeting because it sets a mindful tone. I presume that sentiment was issued by one Mr. He Qinghua, because farther down the page, it states, "All Audio-GD's products are designed and developed under the leadership of Mr. He Qinghua." When I began my auditions, I took this salutation as an advisement, making it my plan to study Audio-GD's Vacuum HE1 XLR line-level preamp with as much wisdom as I could muster and the enthusiasm of high expectations.

The digital ground seems to shift weekly. While firmware and software updates over the Internet somewhat slow the constant upheaval, when you do buy something, you just know that as soon as you plunk down your cash, something new will come along.

So, especially with preamplifiers, why not produce a design based on modules that the user can swap in and out, to custom-configure the preamp to that user's current needs while leaving room for later expansion? Why pay for six inputs' worth of stuff when at present you need only two? Upgrades? New features? No problem—swap out a module. Or, if a circuit in one module malfunctions, you can send only that module back for repairs, not the whole thing.

If any single link in the audio chain should be free of sonic personality, it's the preamplifier. Though a preamplifier's basic job description is "source selector with volume control," from hi-fi's earliest days preamps have been the designated dashboard: the more dials, switches, and lights, the better. All that control came at the cost of quiet, transparency, and tonal neutrality. Still, the quixotic quest for the mythical "straight wire with gain" continued to lead to minimalist designs, including impractical unbuffered "passive" preamps, in which cable length, thus capacitance, affected frequency response.

It's been 10 years since Balanced Audio Technology (BAT) introduced their first products: the VK-5 line-stage preamplifier and the VK-60 power amplifier. (I reviewed">http://www.stereophile.com/tubepoweramps/766">reviewed both in the December 1995 Stereophile, Vol.18 No.12.) The success of these and other BAT products has allowed designer Victor">http://www.stereophile.com/interviews/767">Victor Khomenko (the "VK" of the model designations) and partner Steve Bednarski to quit their day jobs at Hewlett-Packard; they were joined by Geoff Poor as a partner to handle the sales end of the enterprise. BAT's current lineup includes several preamps, phono stages, a CD player, and tube as well as solid-state amplifiers. The top of BAT's preamp range is the VK-51SEhttp://www.stereophile.com/tubepreamps/1103bat">VK-51SE;, which costs $9000; their top tube power amp is the VK-150SE">http://www.stereophile.com/tubepoweramps/536">VK-150SE monoblock ($17,000/pair); if you want their best phono stage, the VK-P10http://www.stereophile.com/phonopreamps/871">VK-P10; will set you back $8000.