Preamplifiers Are Still Getting Better All the Time (Vol.2, No.2: 1979)

Yes, Preamplifiers Are Still Getting Better All the Time: Audionics RS-1 ; Audire 'Legato' 535; Bauman PRO-400 ; Hegeman 'Hapi Two' ; Precision Fidelity C7 PS III and PS LCC.

No new SOTA ratings this time, but some of the lower-priced preamps are beginning to sound so much like the best that maybe everybody has been slowly but surely moving in the right direction after all.

We're still putting all preamps through the various "black box'' bench tests discussed in our earlier issues, but it's becoming quite clear that such tests reveal only obvious design errors and specific malfunctions, rather than the engineering subtleties that separate good, better and best.

(See also our comments on power amplifiers in this regard.) Elusive dynamic distortions are impossible to read out direct ly on meters and CRT's; one must go by indirect, inferential routes from possible symptoms to likely conclusions. It isn't an exact science, and there's still no substitute for the long-suffering listening comparison by insertion into a known reference system of high resolution.

High resolution-there's the rub. You don't get it by using a Shure V15 Type IV cartridge, which is electrically a 13-kHz low-pass filter network; you don't get it by neglecting the lateral and vertical tracking angle alignments, which can result in as much as 5% FM distortion; you don't get it by A-B-ing everything through AR speakers, which ignore the time domain as a matter of fundamental design philosophy.

How many preamp reviews have you read that were based on listening tests implemented with perfectly aligned moving coil cartridges having line-contact styli, with properly isolated and deadened turntables, with electrostatic speaker systems-need we go on? No wonder that all preamps sound the same to so many reviewers; don't all furs feel the same through wool mittens and don't all wines taste the same through spearmint chewing gum? The preamps reviewed below were inserted into our Reference A system (see up dates elsewhere in this issue), and the sonic differences we perceived may quite possibly not be resolved by the demo setup in your dealer's showroom.

This time some of these differences were surprisingly small, but not for the reasons that would be assumed by the all-preamps-sound-alike faction. (Yes, we do measure the RIAA equalization to the nearest 0.1 dB; yes, we do match volume levels when we A-B. Try again.) The principal reason is that when two designers working independently both understand what the problem is, they may come up with different solutions, but there will be a convergence toward functional truth, i.e., correct performance. Two 100% correctly performing preamplifiers should sound indistinguishable from each other, no matter how different they are in circuit design; it isn't quite happening yet, but the differences in some cases have been getting smaller and smaller. We still haven't found anything to equal the Cotter System 2 in transparency, dynamic range, resolution of detail and day-to day consistency of performance; unfortunately, the total price of the five modules is now a staggering $3280, of which the three that correspond to other ''complete'' preamps add up to $2230. Of these three, the CU-2 Control Unit, at $1450, doesn't really exist yet, the dozen or so physically uncouth ''engineering models'' made for a few dealers and professional users being the only ones around. The production version will be coming soon, we're told.

The encouraging thing, however, is that a number of far less expensive preamps give almost as good sonic results as the Cotter. This was not the case until very recently. Whether these lower-priced preamps will sound as good after five years of use as they do when they're new is another matter altogether. Ruggedness of construction and quality of parts still appear to be pretty much in proportion to price. It's only intelligent circuit design that has become cheaper.

Audionics RS-1

Audionics, Inc., Suite 160, 10950 SW 5th Avenue, Beaverton, OR 97005. RS-1 Preamplifier, $699. Three-year warranty. Tested #25030, on loan from manufacturer, and #25072, on loan from dealer.

This highly appealing unit-well built, versatile and nice to handle-is imbued with the kind of engineering integrity and basic good sense that Audionics stands for in our book. Sonically it also rates high; it must surely be one of the top six or seven preamps we' ve listened to so far, regard less of price. Just a year or two ago, we would have raved about this degree of clarity and neutrality; today, however, the RS-1 represents neither the best sound there is nor even the best sound for the money. The best combination of reliable circuitry, quality construction, features and sound for the money-maybe.

What the RS-1 lacks in audio quality, and what even some of the less expensive new preamps approximate more closely, is that ultimate degree of transparency and delicacy of detail, combined with a total absence of nasal colorations, high or low. Not that the RS-1 isn't quite excellent in all these respects; it just doesn't make it all the way to the finals. The earlier of our two samples also had a very slightly hard or strained quality on some kinds of program material; the second sample sounded quite sweet and smooth.

Threshold-level imperfections like these won't show up on the laboratory bench; just in case anyone should suspect the RIAA equalization, it's right on the button below 1 kHz and rolls off just a hair more than it should at the higher frequencies, the error being -0.35 to -0.45 dB at 20 kHz, depending on the sample measured.

Many users will appreciate the excellent tape-copying facilities; others will be intrigued by the ''axial tilt correction'' feature, which is a somewhat oversimplified at tempt to correct electronically for the least important mis alignment of the pickup stylus, namely lack of perfect perpendicularity as viewed from head-on. A test record is sup plied to calibrate the adjustment; the whole thing is a nice little extra touch that shouldn't influence the audio purist's buying decision one way or the other. All in all, a very honorable effort.

Audire 'Legato'

Audire, Inc., 9576 El Tambor Avenue, Fountain Valley, CA 92708. 'Legato' Preamplifier, $330. Three-year warranty. Tested #4071, on loan from manufacturer.

We're tempted to praise this cute little pancake-style (only 1%" thick) preamp for its surprisingly good sound at a price where we didn't expect much, but we realize that we never really heard what it sounds like. It has a kind of built-in tone control in the form of grossly inaccurate RIAA equalization.

The RIAA error curve of the preamp fills out a strip 1.7 dB wide. You could cut this in half and say that the error is + 0.85 dB, but that would be misleading. Most of the error is minus, in the form of a giant saddle starting at 1 kHz, dipping to approximately -1.25 dB in the 8 to 9 kHz area, and curving back to the zero line at the ultrasonic frequencies. That gets rid of a lot of high-frequency energy right in the region where an over-bright or edgy quality will intrude if the circuit suffers from certain common design flaws. The Audire unit just barely flirts with such high-frequency stress on program material that readily provokes it; to our ears, it appears to be better in this respect than many far costlier preamps. But what if the RIAA equalization were restored to normal? Would there be a lot more zip and hardness? We have no idea. There would be a slightly different tonal balance, that's for sure.

So all we can tell you is that the Audire 'Legato' is well constructed considering its price, has a nice open sound without attaining the ultimate in transparency and inner de tail, doesn't seem to have any obtrusive colorations, and would probably sound somewhat different with accurate phono equalization. That eliminates it from audio purist consideration, but a corrected version should be very interesting.

Bauman PRO-400

Bauman Research Instruments, Inc., Route 1, Box 52UA, Rosen berg, TX 77471. PRO-400 Stereo Preamp, $1050. Five-year warranty. Tested early production sample, on loan from manufacturer.

This is a very ambitious high-end audiophile product; just how ambitious should be apparent from the manufacturer's announcement that later production runs will be converted to Camac connectors, a la Mark Levinson. That $1050 price tag also has a Levinsonesque déja vu about it; that was the price of the old JC-2, before the ML-prefixed, silver-wired Saudi Arabian status symbols spiraled up to the multi-kilo-petro-buck bracket. The Bauman, however, also offers a switchable moving-coil head amplifier plus tone controls as part of the package.

Interestingly enough, the Bauman PRO-400 sounds very much like an early ML-1 with a little extra zip. In other words, very open, very clean, very quiet, but rather hard, bright and fatiguing. In addition, we discern in the Bauman a characteristic midrange coloration of its own. Frankly, it isn't an acceptable sound to the perfectionist ear.

On the test bench, the PRO-400 performed beautifully.

In fact, our impression is that it was designed to perform beautifully on the test bench, rather than in the ear of the beholder. The spec sheet and the promotional literature abound in very small and very large numbers; any reference to music appears to be deliberately avoided. We suspect the presence of some of the elusive feedback-related problems discussed at length in our seminar, but we made no heroic effort to track them down. On all routine tests the PRO-400 comes through with flying colors, confirming the spec sheet in every respect, including those beautiful square wave photographs. The RIAA equalization error is nil above 1 kHz; at the lower frequencies there's a broad saddle dipping to -0.4 dB in the 100 to 200 Hz octave, an anomaly pre dictable from the topology used but still within specs.

Physically the unit is very well made; its switching and control facilities are quite complete; we wish we were able to be more enthusiastic about it, but we know we could never live with that overbright sound.

Hegeman 'Hapi Two' Hegeman Audio Products, Inc. (Hapi), 176 Linden Avenue, Glen Ridge, NJ 07028. Hapi Two preamp/control unit. $900. Two-year warranty. Tested #600, on loan from manufacturer.

There isn't really anything new to report about the Hegeman preamp circuit, which remains unchanged in this new and very stylish extra-flat package with brushed aluminum relay-rack panel. We just want to make it official that we've tested it again and it's as good as ever, perhaps even a little better in the latest production runs, as a result of more completely systematized manufacturing and quality control procedures. It sounds simply beautiful.

From phono input to main output, the only preamp known to us with even greater transparency and resolution of detail is the more than twice as costly Cotter, the control module of which isn't really in production yet. Comparing phono sections only, the PS III is also superior to the Hapi in these respects, but the PS Linear Control Center is not as good as the high-level section of the Hapi, so that the straight-through sound of the latter is somewhat superior to that of the PS system. What all this adds up to is that the Hapi Two is the best all-in-one preamp/control box we've tested that you can buy right this minute, as we go to press-regard less of price.

Considering that we first told you about the Hegeman preamp more than a year and a half ago and that the circuit has gone through only very minor modifications since (and none lately), it has held its high ranking with remarkable consistency on rapidly shifting ground.

Precision Fidelity C7 Precision Fidelity, 1238 Green Street, San Francisco, CA 94109.

C7 cascode preamplifier, $499.95. One-year warranty (tubes 90 days). Tested #79840, on loan from manufacturer.

The first thing that needs to be pointed out about this outstanding and attractively priced audio component is that it isn't really a complete preamp/control unit. It has no high level stage. It consists basically of the excellent phono stage of the C4, with the gain boosted to 50 dB at 1 kHz, followed by a level potentiometer (one per channel, no double-deck stereo volume control, no conventional balance control) and facilities to select various high-level sources (tuner, aux, tape monitor) without additional amplification. If these sources don't have enough output to drive your power amplifier-forget it. In most cases it works out just fine, as long as you remember that those potentiometers create a fairly high impedance source, as high as 7000 ohms depending on their setting, so that you need low-capacitance output cables to avoid rolling off the highs.

The phono sound of the C7 is slightly different and, if anything, even more appealing than that of the C4, which did very well indeed in our previous series of tests. The C7 has a totally smooth, unstrained and edgeless sonic character, with tremendous dynamic headroom, giving the impression of a sweet, mellifluous, luxuriously cushioned quality that some listeners find more ''musical'' than the more transparent, analytical and airily detailed sound of the best transistor preamps (Cotter, Hegeman, PS III). The C7 is very easy to listen to, perhaps just because it wraps this pleasant softness around the music-almost a kind of veil-but for that very reason it must ultimately be judged less accurate than the solid-state contenders for top ranking.

At first we suspected that some kind of RIAA equalization error was responsible for this 'personality' of the C7, but that didn't turn out to be the case. We measured virtual perfection from 1 kHz on up; the lower frequencies were uniformly depressed along a -0.3 dB shelf, dipping to -0.5 dB at 150 Hz-certainly nothing dramatic. Another possibility was high-frequency mixing or cross talk between the stereo channels, which tends to create a softening effect, but the measured separation was excellent. Square waves also looked quite good at all frequencies; in fact, we detected no glaring anomalies of any kind, anywhere. Correlating the characteristic sound of the unit with measurable data would obviously require extensive detective work, with no guarantee of success.

None of the above should be interpreted as a lack of enthusiasm for the C7. If those three solid-state preamps didn't exist, the C7 would be in our ' 'Reference A'' system, and we would be happily listening to it without much aware ness of what we were missing. It's that good.

PS III and PS LCC

PS Audio, 3130 Skyway Drive, #301, Santa Maria, CA 93454. PS II Phono Preamplifier, $222; PS Linear Control Center (LCC), $240; optional rack panel, $25. Five-year warranty. Tested #0393 and #0362L, on loan from manufacturer.

Paul and Stan (the P and S of PS Audio) have come a long way since the PS II plug-in phono stage we reviewed two issues ago. The similarly conceived and configured but vastly improved PS III is now just a very small step behind the Cotter PSC-2 in sonic accuracy (at a ridiculous fraction of the cost!), and the Linear Control Center, though not as amazingly transparent and neutral, also sounds truly excel lent. The entire system, which will set you back all of $487 if you buy the single-piece rack panel that ties together the two little self-contained boxes, is our obvious and unequivocal selection for the front end of ''Reference B."' It could even qualify as a temporary ' 'Reference A'' preamp while waiting for the entire Cotter System 2 to become available on a regular production basis.

The only difference in sound between the Cotter and PS phono stages is a very slight tendency by the latter to displace high-frequency information forward, toward the listener. In more exaggerated form, this anomaly ends up as over-bright ness or hardness; in the case of the PS III it's barely perceptible. The two units have virtually the same sound, which is in effect no sound; it takes electrostatic speakers and a very fine power amplifier to zero in on the differences. It's interesting to note that both operate in the current mode and both are passively equalized for the RIAA playback characteristic.

Talk about a convergence toward functional realities ...

As long as we're talking about RIAA equalization, it should be pointed out that the PS III is right on the button, +0.0 dB, from about 50 Hz on top to ultrasonics; at 20 Hz the error is a staggering -0.2 dB. (That includes our possible measurement error.) So you see, all you engineering geniuses, it can be done for no money at all, with just a little bit of devotion. All other things check out equally well on the PS III, including pre-equalized square waves, cross talk, you name it. All in all, we're unaware of a third phono preamp that isn't some distance behind the PS III, at any price. That statement applies, however, only to the “moving magnet” position of the gain switch; the ' 'moving coil'' position is no substitute for a good transformer or even a good cheap pre-preamp like the Marcof. We almost wish, for the sake of this breakthrough product's credibility, that the extra little MC feature hadn't been thrown in. It sounds bad, whereas at normal gain the PS III sounds incredible.

The LCC unit has a few minor problems, including a bit of cross talk, all tending to create a very slight veiling effect.

Even so, the PS III cum LCC still sounds cleaner and more transparent than other complete preamp signal paths we've tested, with the exception of the Cotter and the Hegeman. For the money, that's still incredible. Of course, if your power amp has level controls (only a few do), you can eliminate the LCC altogether. The PS III has plenty of gain.

The construction of the PS units is a mixed bag of credits and demerits. The metalwork has only very recently been changed to anodized aluminum; the earlier painted boxes were simply atrocious in appearance, with misaligned screw holes and barely fitting tops and bottoms. Inside one discerns an obvious attempt to spend the money where it does the most good and skimp on whatever is less important. It's an intelligent trade-off but some purists who won't be able to resist the sound will miss that reassuring mil-spec look. The basic question is whether the sound will be exactly the same after years of daily use. That remains to be seen.

For the moment, we're all admiration with hardly any reservations. This kind of money in the past has always bought a formatted sound with characteristic colorations you could either like or dislike; now for the first time, achromatic preamplification is cheap.

Recommendations

This time, they're obvious and require no further explanation if you've read the reviews above and in the previous issue.

Best preamplifier so far, regardless of price: Cotter System 2.

Best preamplifier per dollar: PS III with PS LCC.

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[adapted from TAC]

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Also see:

Box 392: Letters to the Editor

Why We're So Mean, Vindictive, Arrogant, Negative--and Truthful

Various audio and high-fidelity magazines