Convergent Audio Technology SL-1 preamplifier Jonathan Scull 1994
When I first landed safely on Planet Stereophile, JA asked me a loaded question: How would I feel about comparing the two preamplifiers in my system at the time—the Convergent Audio Technology SL-1 Signature (my longtime reference) and the Jadis JP-80MC? How does one decline such a request?
As often happens in High-End La-La Land, this delectable contest was put on hold until Jadis changed the capacitors they were using in their unit, and DO had concluded his review. The current-production, Philips-capped version—finally coaxed from fellow tube-lover Monsieur Richard Ol-share's grasp and measured by TJN—was dispatched to my waiting system.
When I contacted Ye Olde Editor to announce the Jadis's arrival, he updated the article's raison d'être: "Jonathan," he said, "should a CAT owner dream about one day owning a Jadis JP-80MC?" Hmmmmm. Food for thought.
The similarities and telling differences between these two preamps speak eloquently of the wildly disparate cultures that concocted them. This was going to be fun—if a little dangerous. Of course, both countries have circumstances to live down. Let's not forget l'affaire Edsel. Recall, too, that Jerry Lewis is much admired in France. There, I think the books are balanced. Shall we move on?
The cat in the hat
The CAT looks Lab-Grade Chic (especially in all-black livery) in its hernia-inducing, mass-damped chassis, augmented by internal surfaces covered with (ironically) a vivid, French-blue damping material. The exposed screwheads make it look businesslike and cobbly—especially when raised on footers of one type or another.
The separate power supply is housed in a small but heavy chassis containing the transformer and some supporting circuitry. The regulation for the tube heaters and the first stage of regulation for the audio signal live here; designer Ken Stevens feels that all subsequent audio-signal regulation must be physically close, for more precision.
A very few CAT owners may experience the ills of RFI entering the unit, either through the umbilical between the control unit and the power supply, or in another fashion. During one of his infrequent visits to NYC, Ken remedied a good 80% of the RFI that had plagued our unit; should you also have this problem, he can help. I'm aware of only one other case of an unsalvageably hissing CAT: from a fellow scribe who lives between the Empire State Building and the World Trade Center, in the middle of Microwave City. Ken informs me that only a few incidences of Demon RFI have been reported by the many people around the world using CATs. I'm listening to a Clearaudio Signature phono cartridge (0.6mV) as we speak, and the CAT has plenty of clean and quiet gain to burn.
I've owned three CATs over the years (one Reference, two Signatures), and they've given me literally zero problems. For those counting, tube-saving soft-start warmup time is 90 seconds from Standby to Operate; a newer unit takes a full two minutes before you can step on it. The CAT sounds good after about 20 minutes, but it needs the same one-hour warmup as the JP-80MC before the fat lady really sings.
Cat tube matters
The CAT's tube-filled interior is a sight for sore ears. Under that heavy top plate are a pair of Sovtek 6DJ8s serving as left and right phono inputs, followed by a pair of 12AX7s for gain, followed by a single Sovtek 6DJ8 output (cathode follower). Same arrangement on the line-stage, except it has a pair of 12AU7s serving input duties. This is the most ticklish tube pair in the CAT; it takes time and luck to find a closely matched pair of 12AU7s that don't spit and splutter. If they're noisy in the George Kaye Labs Tube Tester, they'll make a racket in the CAT's line inputs. All other tube positions are filled easily enough (even the phono inputs), although in order for the CAT to perform, you've still got to have tubes that measure well and sound good.
If you're measuring, T1 (triode one of a dual-triode preamp tube) is more critical than T2, so bear that in mind when you slip surreptitiously out of bed in the middle of the night for a measuring session. (You wouldn't want to do this in front of anyone else, would you?) Of course, changing the phono inputs can drastically change the sound, but we're happiest with the Sovteks. Forget vintage tubes for the CAT—stick to Ken Stevens's approved factory tubes (a mix of Sovtek, German, and Yugo Nationals). This advice comes from a guy with a drawer full of tubes—under hard audio-reviewer use, I get about a year from a fresh set.
The ultimate CAT tweak is to get a new one. Ken has a habit of upgrading the unit slowly, without changing the model designation. This way his fans won't suffer from rampant Upgrade Nervosa at the drop of a model suffix. But how bad can a CAT be? Still, most current units are significantly "better" than those of a year ago. But don't faint dead away yet—CAT offers a factory upgrade. Just give Ken a call and crunch some numbers with him. Any unit with a serial number greater than 5400 can get the full treatment. Believe me, it's worth it.
As set up in our system, the CAT is slightly compressed. (It's in a Michael Green Designs ClampRack. [badaBOOM!] I can't help myself.) The ClampRack is more effective with the JP-80MC; the CAT changes but little when clamped due to its damped, heavyweight, "pretuned" chassis. When clamped, it sits on three of the smaller Audiopoints (two front, one rear), with one centrally located up top. I also enjoy especially musical results with the CAT when it's being supported by Shun Mook Super or Ultra Diamond Resonators. The larger Audiopoints, which also do the Drain the Vibe Transfer Thing (to a lesser extent than full clamping), are good choices as well. Ken likes his factory-supplied squidgy O-ring feet the best, but he's open-minded. Sort of. He's designed a preamplifier "system," not just a box.