Audio Research SP-11 preamplifier Anthony H. Cordesman November 1986
The sound of the Convergent Audio SL-1 is very good indeed (as it should be at $3495)—good enough that it can probably be best reviewed by comparing it to its top competition. The Audio Research SP-10/II and SP-11 are obvious standards of reference in tube design, and the original and revised Motif MC-7 are good transistor standards of comparison.
Bass: The Audio Research SP-11 has a notably different sound character [to the Convergent Audio SL-1]. While the revised Motif MC-7 is perhaps a bit too rich and warm in the transition area between bass and midrange, the SP-11 is extremely transparent and extended in the deep bass, without a touch of extra bloom or control loss; it's just a touch too lean, however. The C.A.T. SL-1 is very similar to the Audio Research SP-11 in this respect, with perhaps a little more overall energy.
Upper Bass/Lower Midrange: Both versions of Conrad-Johnson's Motif MC-7 make a smooth and coherent transition from bass to midrange. Once again, however, the MC-7 is a bit less dynamic and "live" than the Audio Research SP-10/II. The SP-11 and the Convergent Audio Technology SL-1 are similar to the Motif MC-7.
Midrange: All four preamps provide superb performance in the midrange. They should, and no audio equipment is worth a damn that doesn't. The SP-11, however, performs best, with the Convergent Audio Technology a close rival...The SP-11 seems spot on, and is amazingly revealing in this part of the frequency spectrum. The SL-1 has much the same tonal character as the SP-11, but lacks a bit of its natural dynamic energy.
Upper Midrange: All four preamplifiers sound very different in this area, but all are very listenable and musically involving without producing artificial emphasis or fatigue. The C.A.T. SL-1 seems exceptionally accurate. It does an outstanding job of reproducing what is on the LP or CD, good or bad. Once again, however, the Audio Research SP-11 seems superior in terms of overall tonal accuracy, dynamics, and detail—particularly in soft passages. It would be nice in some ways, however, if the SP-10/II were accurate; it makes most recordings sound like music. The SP-11 and SL-1 reveal the unfortunate fact that most recordings sound like recordings.
Treble: The Audio Research SP-11 again has the lead, but the C.A.T. is a very close rival. The SL-1 also has a slightly better top-octave performance—at least according to those female members of my family that insist on hearing everything in this region.
Soundstage Depth: The Audio Research SP-11 seems a bit more realistic than either the MC-7 or SP-10/II, but has less apparent depth with most records. The SP-11 does, however, suddenly acquire more depth and detail when the record or tape actually has the information. Once again, the Convergent Audio Technology has much the same sound character as the SP-11, and is only slightly less detailed and revealing.
Soundstage Imaging: All four preamps do a consistently good job of portraying imaging on both the simplest and most complex music—a consistency normally lacking in even the most expensive competition.
Both the SP-11 and C.A.T. SL-1 tend to favor the center—only slightly, provided that extreme care is taken with the balance control to get things exactly right, which isn't easy with stepped balance controls. This may or may not indicate that the MC-7 and SP-10/II romanticize the imaging.
Soundstage Hall Position: retains the traditional tendency of CJ equipment to make it seem if you were sitting mid-hall, rather than forward, although the improved MC-7 clearly outperforms the Premier Three and any previous CJ preamp at making this seating position seem realistic. There are many small musical details—hall noise, percussion transients, bowing noises, etc.—which come through during phono playback using the MC-7 that are blurred or missing with the Premier Three. These details also come through in a musically natural way. In fact, the more you listen to the Motif, the more you will notice additional data about a recording's location, multi-tracking, and/or mixdown.
The Audio Research SP-10/II and SP-11 have a more forward character [than the improved Motif MC-7], but are both very revealing. If the MC-7 is Row N, the SP-10/II is row H, the SP-11 rows E-F. The Convergent Audio Technology is Row F-H.
All four preamps have a consistent ability to place you in the hall. The Motif MC-7 makes you sink back into the music, almost relax into it as you find yourself listening to the full atmosphere, harmonic detail, and timbre natural to a mid-hall seating position. The Audio Research SP-10/II remains the most attention-grabbing preamp ever made. You feel like you are in the best seat in the house even as your mind tells you that the SP-10 may be improving slightly on the signal source to give you this impression.
The Audio Research SP-11 and C.A.T. are less musically involving, but are also probably more neutral. They do a more realistic job of reproducing records and reflecting the differences in apparent listening position, without imposing the preamp's sound character of the preamp. At the same time, you are less likely to hear hall or listening position effects on records where the presence of such information is uncertain.
Overall Dynamics and Transient Life: The SP-11 is a bit restrained in comparison with both the MC-7 and SP-10/II, but this restraint seems more natural in prolonged listening. It is superb in reproducing the full impact of dynamics and transients from the softest passages up.
Sonic Consistency No Matter the Gain: Both the Motif MC-7 and Audio Research SP-10/II suffer from slightly higher coloration in their high-level stages than do the SP-11 and Convergent Audio Technology SL-1. The SP-10/II can be switched in a number of ways to reduce coloration in the high gain stages, and seems remarkably neutral (until you hear the SP-11)...The SP-11 is probably the most neutral and flexible preamp ever made at every combination of its gain stages. It is sonically consistent with all but the very lowest output moving coils (such as the Audionote and Ortofon MC-2000). At the same time, there are a wide range of combinations of gain, allowing you to remove small amounts of coloration, but at the cost of also removing what are often very necessary and useful features (see JGH's review in Vol.9 No.4).
Most audiophiles will be far better off if they leave in the gain stages that include the balance control, since precisely balanced power response is virtually unheard of in real-world listening rooms. Incorrect balance is far more damaging to the imaging and soundstage than the slight loss of transparency introduced by the balance control and extra gain stage. At least half the time the user will also be better off using the high-level gain stages to create a proper gain match and suitable buffering between high-level inputs and power amp. It is easy to trade one form of coloration for another, and, while transparency may benefit, the wrong match will restrict dynamics and slightly slant the overall timbral balance in favor of the upper octaves.
Not Ranking the Top Preamps: Hoos on Filst? For the vital question of how to rate the four preamps? Well, the latest version of the ARC SP-11 (footnote 1) still defines the state of the art—as well as the state of the price tag! For the purposes of this review, however, what's important to know is that the C.A.T. is good enough to compete head on with the best, and offers a new and important blend of sonic qualities.
You can't have everything in one preamp; if you feel that a Porsche should also be a Rolls Royce, then no preamp will meet your needs. At the same time, if you want a preamp that will help you extract natural musical pleasure from a wide range of recorded material, then all four of the units discussed here can do an excellent job. At this level of quality, the question "Who's on first?" is strictly for Abbott and Costello..—Anthony H. Cordesman
Footnote 1: This latest version of the SP-11 is an unannounced in-production update that AHC received after most of the listening for this review was completed.—Larry Archibald