Solid State Preamp Reviews

There are some standing jokes in the audio industry about the qualities a piece of equipment must have in order to be truly "high-end." One definition is that it must be unavailable, unreliable, and dangerous. Another is that it will sound great, break, and its manufacturer go out of business. By meeting at least half of these variables, the Spatial Coherence TVA-1 preamplifier qualifies as a classic audiophile product.

Manufactured and marketed by Spatial, Inc. for three years (the last reference I was able to find was the 1981 Audio magazine annual equipment guide), its claim to fame was the proprietary amplifying device, the Knapp T-FET Valve, a patented invention of R.P. Knapp, who was also, I presume, a major figure in the Spatial organization. Knapp's particular bugaboo was the phenomenon of noise intermodulation—the addition of thermal noise to low-level musical signals by such ordinary devices as tubes, transistors, and op-amps—which he blamed for glare, dynamic incongruities, and imaging problems. The test results listed in the heading show that his preamp does indeed have a low noise floor, especially for a unit ten years old. Other test results likewise qualify the TVA-1 as an "audiophile" component.

As far as I know, this preamplifier is the only product Spatial ever made. It was introduced at a price of $1395 and rose to $1600 before the manufacturer threw in the towel. What we have here is not merely a classic piece of hi-fi, but a classic hi-fi story: put all your eggs in one basket, then drop the basket from the top of a very tall building.

Construction quality is generally good: a thick, all-metal chassis, gold-plated connectors, sealed switches and potentiometers, a double-sided epoxy circuit board, and a shielded power supply. Four T-FET Valves, large epoxy monoliths, are squarely mounted on the main board. Two are used for phono gain and two as line amps. Equalization and overall gain are fixed by external networks of capacitors and resistors, not unlike an op-amp design. Op-amps these are not, however; I measured 150V across the main power-supply filter capacitor.

There are some kludges: the power supply is built on what appears to be a computer-surplus printed circuit board, some of its traces going nowhere and others terminating in "fingers" intended to mate with an edge-card connector. This board stands off the chassis via rubber stick-on feet, of the same type which are on the bottom of the preamp. Gaining access to the interior involves the removal of all the knobs and nuts holding the controls to the front panel, as it and the top cover are assembled as one unit. This means any simple repair (such as replacing the indicator LED, which I had to do) is needlessly time-consuming. Imagine a car which requires the removal of the hood and fenders in order to change the spark plugs.

Listening
The owner's manual cautions against connecting the TVA-1 to a power amp for at least an hour after turn-on, as the "valves" are slow to stabilize and will emit strange gurgling and rattling sounds until they settle down. No muting is provided. I was cautious and let it cook for a full day before listening.

When I did, I was pleasantly surprised. It exhibited a fairly deep, if not wide, soundstage, with instruments clearly separated and spatially stable (hence its name). Bass was somewhat mushy, this owing to what I perceived as an overly long decay. Although the frequency-response measurement shows a small rise in the midrange, and that only in the right channel, upon listening mids seemed a bit recessed, in keeping with this unit's spatial character. Female vocals and strings took on a slightly gritty edge, which was not unpleasant but reminded me of listening to old or under-biased tubes. Highs were soft and not extended; articulation of detail was adequate. Long-term listening (for me, more than an hour) did not induce fatigue, but neither did it generate excitement. I wondered how it might sound in harness with a power amp of similar vintage, like the Ampzilla.

I compared it side-by-side with a Harman/Kardon Citation 21 (footnote 1), not because the H-K is a world-class preamp, but because I have been using it for several months and know it well. Also, it is available at discount for not much more than the Spatial goes for used. An interesting comparison: a ten-year-old formerly state-of-the-art preamp vs a current mid-priced one. On the basis of performance alone, the H/K beat the Spatial in every category but one—depth of image. This is where the TVA-1 excelled, albeit just slightly, and I wouldn't call its imaging ability anything special by modern measure. The Citation had tighter bass, a bigger, more forward soundstage, and better detail. This is what finally tipped the scale for me; the song "Hobo's Meditation" on the Trio album contains the words "tough cops and brakemen." This phrase was clearly articulated by the Harman/Kardon, whereas the Spatial rendered it more like "cough cause and break-in." Perhaps this is indicative of how far the audio art has progressed in a decade.

This is the second specimen I have encountered of the TVA-1. The first was a repair which crossed my service bench three years ago. It had a channel out in the phono stage, the result of a defective "valve." There was nothing I could do for it but give it back to its owner with an apology and an explanation that parts were simply not available.

Conclusion
Occasionally, this preamp will crop up in one of the used-equipment publications. I think it has a certain value as a collector's item or as the heart of a second system. It also has some potential as a modification project; I wonder what a serious capacitor upgrade and a low-impedance outboard power supply might do for it. Steve McCormack of The Mod Squad also wondered about this. For several years after the demise of Spatial, he offered his "MacMod" at $1350 a pop to anyone rich enough to take him up on it. I understand from a friend who owns one that this modified Spatial is really quite wonderful. Unfortunately, service on it is no longer available, as a phone call to The Mod Squad will confirm.

At its typical used price of $350, there is a lot of competition both in new and used equipment: a used Musical Concepts modified Hafler 110 goes for $350–400, and it has a removable top, a bottom access panel, industrial-standard parts, is easy to repair, and has a reasonable warm-up time. If you don't have a phobia about op-amps, the B&K Pro-5 and the Adcom GFP-555 are both good values. The Harman/Kardon Citation 21, mentioned earlier and usually ignored in high-end circles, is an excellent performer for just a little more. Best deal of all is the Superphon Revelation Basic Dual Mono, which Sam Tellig loved at its close-out price of $399. It can be found used for $200, and is one of the best preamps I ever heard in my system.

Owning a Spatial Coherence Preamp is like owning an Edsel; owning the modified version is like owning an Edsel with Ferrari performance. In either case, you have a genuine artifact of its time and a nice conversation piece, even a decent car, but you don't have serviceability. For this reason I strongly suggest that you think twice before buying the TVA-1 with the intention of using it as your only preamp. If you do, be sure you have a backup. When it breaks, you can place it alongside the Accutrac turntable and Corona Ionovac gas-plasma tweeters in the Extinct Oddities wing of your hi-fi museum.

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Footnote 1: J. Gordon Holt reviewed the earlier Harman/Kardon Citation Eleven preamplifier in April 1977.—Ed.