Tube Preamp Reviews

This very expensive, two-chassis, dual-mono, all-tube preamplifier was formally reviewed by J. Gordon Holt last November (Vol.11 No.11). While bothered by the dual volume controls with their too-large steps, the clumsy tape-loop arrangement, and the high line-stage gain, Gordon felt that it came as close as any tube preamp he had heard to being perfectly neutral, with a line stage that was "effortlessly sweet, open and airy, yet immensely detailed." However, he felt that the line stage, and to a lesser extent, the phono stage, thinned out the sound a little below 50Hz and concluded that, while the Premier Seven didn't sound like a tubed design, at its price level, $8000, it would have to be perfect to justify its purchase when Class A solid-state preamplifiers could be had for significantly less.

Enter the Conrad-Johnson PV9 preamplifier, which I reviewed in May (Vol.12 No.5). This tube preamplifier gave a superb sound from LP, though its phono stage's low sensitivity/highish noise level made it unsuitable for use with normal MC cartridges. Thus it was that I arranged to audition the Premier Seven, hoping that it would offer at least the same standard of LP sound that I had experienced from the PV9, but with a lower noise level, rendering it more compatible with my preferred Linn Troika cartridge.

Well, the intrinsic noise was lower, but it was still of the order of groove noise. Lowish-output MCs should best be avoided. But the sound from LP was stunning. Plenty of bass weight without any boom or sogginess; a clean, detailed midrange; and highs that soared. Bypass testing using the Mod Squad Line Drive suggested that the Seven's line stage was very slightly veiled in the mids, as well as having a tad too much bass energy—the opposite of Gordon's finding. But where this preamp shone, however, was in its soundstaging.

Gordon had mentioned the Premier Seven's excellent performance regarding all aspects of soundstage reproduction. Gordon, this preamp's ability goes way beyond that. The world of preamplifiers is divided into three camps: The first grouping is the largest, being comprised of those unfortunate models that refuse to throw an image with any depth at all. You hear the direct sounds of instruments and you hear reverberation, but never the twain shall coalesce to represent what the recording engineer—if he or she were true of heart—tried to capture. Second is the smaller group, representing most high-end preamplifiers of the solid-state persuasion, where the direct sound of sound sources does integrate with the recorded ambience to give a soundstage with perceptible depth. However, that depth is "quantized," as it were, with individual instrumental and vocal images themselves presented as two-dimensional flats at differing distances from the listener. The third and most exclusive group is where individual images are not only presented within the soundstage at differing distances but are themselves possessed of body and depth, rounded as they are in reality. The first preamplifier I heard with this ability was the Audio Research SP-10. For those who say that it is a spurious effect due to the use of tubes, I can only point out that the solid-state Mark Levinson No.26 also does this, as does the all-FET Vendetta Research SCP2 MC-line preamplifier that has become Gordon's and my reference.

Conrad's and Johnson's Premier Seven joins that select grouping. Listening to my own tapes, instruments palpably sounded as I had intended them to sound, the spatial resolution being unambiguously what I had aimed at with the various microphone techniques employed. This, for me, is a paramount aspect of reproduction, for without that feeling of locked-in certainty about where things are in space, I find the stereo illusion much less gratifying. And remember, it is an illusion. You may think that you are hearing a centrally placed singer with a number of instruments behind and to the sides of him or her, but actually you are hearing two separate, varying sound pressures from two individual speakers. Being an illusion, consisting of a fleeting series of correlations drawn between those two independent signals, the sonic image is very fragile; it takes designers of talent to produce an electronic component that preserves the illusion intact.

Overall, my feeling is that, yes, the Conrad-Johnson Premier Seven is very expensive. Its ergonomics are clumsy, and its disc-stage noise is only just acceptable with low-output MCs. But it does have the right stuff, the requisite degree of sonic magic to make it a Class A recommended preamplifier.—John Atkinson