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It takes more than passing courage to make another assault on building the world's best tube preamplifier. You face stiff competition from well-established firms like Audio Research, Conrad Johnson, and Counterpoint. Such units can't be made inexpensively, and you face the steadily growing problem of tube supply: it is getting harder and harder to get tubes that are stable, have predictable sound and performance characteristics, and are long-lived. And you have to show audiophiles who have been burned before that you will still be around when they need service.
The balance control could have finer increments, and the power supply is hard-wired to the main preamp unit. All in all, however, the ergonomics are very good, and cartridge loading is easily changeable through plug-in resistors or capacitors. I would have liked another high-level input, but then reviewers always want another high-level input—perhaps their only area of consistency.
The Sound: Comparing the SL-1 With the Best
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…
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.
The Soundstage—Depth: The original MC-7 had superb, if slightly exaggerated, depth. The improved Motif provides this same depth, but with more detail and less exaggeration. it is perhaps the most musically realistic preamp to date in this performance area. The SP-10/II has a bit less depth, placing instruments a bit more forward.
The…
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). It does, however, add a bit of warmth and apparent imaging detail to everything that passes through it, with this coloration increasing in direct proportion to gain. The phono stage is very consistent with the overall character of the high gain stages, and its sound character doesn't change with cartridge loading, but its gain capability is also clearly marginal with many of the lower-output moving coils. It needs a relatively high output mc…
Jack English wrote about the SL-1 Signature in December 1992 (Vol.15 No.12):
The Convergent Audio Technology (CAT) story is actually the story of one man—Ken Stevens. He is an electrical engineer/applied mathematician with two degrees from the University of Rochester. While UR did not have an audio program per se, electrical engineering offered Stevens the best alternative. While a student, he worked on various amplifier and preamplifier designs, all of which were, predictably, solid-state, using transistors and op-amp chips. His first real design was something simply called the "FET…
No CAT story would be complete without a discussion of tubes. Stevens continues to measure and audition every type of tube he can get his hands on, over time finding his favorites. This may sound odd to those familiar with the preamp's evolution—different SL-1s often appear to use different tubes. In reality, though, the SL-1's tube complement has remained relatively constant. Tubes have generally come from the same sources via different suppliers, hence the variety of suppliers' logos on the tubes themselves. For the last eight years, all of the 12AU7s have come from the same German…
The heart and soul of the latest CAT's sound is the glorious midrange splendor of all the music which passed through it. No matter how trite this may sound, instruments simply sounded more like themselves. They were musically rich and lifelike, with body and fullness. At the same time, they were clean and detailed. At no time was the sound euphonically rich or analytically thin. Clarinets were often harsh, brass had bite, reeds were raspy as the occasion warranted, strings were often strident, and voices were, well, human. There was nary a trace of syrupy glaze, artificial warmth, or rounded…
We often wrongly assume that a piece of equipment that sounds natural at low volume settings and can play loudly is dynamic. This is far from the truth. To properly re-create dynamics, a piece of equipment must be able to reproduce all of these various volume levels in proper proportion to one another within the same piece of music. If we hear a piece of equipment that gets the softest and loudest passages reasonably correct, we are then convinced it has good dynamic capability. A significant percentage of today's best equipment can get these extreme volume levels reasonably correct, but…
Depending upon the recording, performers were: in the room with me (eg, Johann Froberger's Works for Harpsichord on Deutsche Harmonia Mundi 7923-2-RC); just back behind the speakers (eg, Orpheus); or well behind the rear wall of my listening room (eg, Dire Straits' San Antonio '85 double-CD import LLRCD 097/098). The preamp itself imposed no particular perspective or hall seat on the music through either the line or phono stage. Performers were not thrust into my lap, nor was I relegated to the top of the balcony (or stadium) on any consistent basis. The Signature wasn't laid-back, nor did…
Jack English compared the SL-1 with the MFA MCR in January 1994 (Vol.17 No.1):
Filet mignon or lobster? That's the level of choice in any comparison of these two superlative tube preamps, the MFA MCR and the CAT SL-1 Signature. Oddly, neither offers balanced operation, as do other excellent tube preamps such as the Melos 333 Plus and Audio Research LS-5. Both use RCA plugs in additional sockets to load their phono sections, while many preamps (eg, the Melos and Klyne) build this flexibility in.
The CAT placed me closer to the orchestra, which was located upon a very wide stage.…