CAT SL-1 Signature Mk II

Category: Preamps

CAT SL-1 Signature Mk II

Context: preamp was purchased to evaluate against my resident phono stage: Aesthetix IO Signature w/dual power supplies. The balance of the system is as follows: Digital – CEC TL-0 Mk II, modified Meitner Bidat DAC. Analog – Vyger Indian Signature TT with Dynavector Karat 17D2 and Ikeda EMPL cartridges. Micro Seiki SX 8000 TT, Schroeder Reference arm with ZYX 1000 Airy 2 cartridge, ELP laser TT.. Cables – Silversmith Palladium IC and speaker cables. Amps – Wavac 833A mono’s. Speakers – stacked Quad 57’s rebuilt by Wayne Piquet. Primary music preferences are singer/song writer, symphony and vintage rock.

The CAT SL-1 has a few interesting construction features which clue the owner in that Ken Stevens takes his design seriously. First off the cabinet of the preamp is constructed of a considerably heavier gauge metal than other preamps that I’m familiar with. The chassis feels almost as if it’s made of cast rather then sheet metal. Obviously this will help minimize acoustic feedback to the inner workings. Taking a look inside reveals that the chassis is further dampened with EAR polymer damping sheets. This is a fairly expensive damping material and is impressive to see it in use by a manufacturer.
The outboard power supply has a similar weight chassis and, unusually, has a permanent umbilical power cord connecting it to the main preamp chassis. While making the handling of the SL-1 a bit more difficult (you cannot disconnect the power supply from the preamp), this does eliminate one connection and prevent possible damage to the SL-1 from inadvertent power supply disconnects ( as can happen with the Aesthetix).
Another interesting feature is the impedance loading jacks for the phono stage. The phono stage is loaded via custom RCA plugs (one set of plugs for each different impedance level) which plug into the RCA jacks adjacent to the phono input. This allows the listener to quickly switch impedance while listening so as to gauge the sonic effects of the changes.

Upon listening to the SL-1 I was immediately struck by two strengths relative to the Aesthetix. First of all the bass is very un-tube like in its power and control yet very tube like in its nuance and subtly. The bass seems to combine the best features of solid state and tube circuitry, thus producing superior quality bass to anything I have experienced in the past out of a preamp . Secondly the SL-1 has considerably less distortion than the Aesthetix. This has two sonic benefits: the music sounds distinctly more life-like in its transparency (thus the SL-1 is significantly more transparent than the Aesthetix). There is also more information coming through on the SL-1. Low level information is revealed where it previously was lost. To me this is best heard in vocals where small inflections and changes of breath become apparent with the SL-1. This combined with the lower distortion and transparency take the listener closer to the real experience. What surprises me all the more is that the SL-1 uses only 6 tubes in the entire circuit to achieve these results, including the high gain MC gain stage. Yet the SL-1 phono stage is also considerably quieter than the Aesthetix. Clearly Ken Stevens is apparently as careful in his tube selection as he is in his circuitry design.
So where does the SL-1 fall short relative to the Aesthetix? The only clear attribute I’d give the nod to the Aesthetix on is its ability to bring vocals forward in the sound stage. This gives vocals more of an ‘in the room’ quality which I find attractive. The Aesthetix has more of a ‘lush’ sound but this comes at the expense of transparency. There is a light ‘haze’ and veil to the Aesthetix when compared to the SL-1. The Aesthetix seems to push the center of the sound stage forward relative to the sides.
The Aesthetix does seem to sound a little more dynamic at higher volume as well. But this may very well be due to higher distortion levels as a function of volume (distortion tends to make things sound louder than they are)
The SL-1 does not sound like a tube unit, nor does it sound like a solid state unit. It combines the best features of both, in my opinion. Low distortion, clear transparency, yet full harmonic integrity and SE – like detail and nuance reproduction - It’s very much of a ‘clear window’ view into the music. This ‘clear view’ however may reveal other parts of the audio system chain that are weaker. I could see where this would lead others to blame the SL-1 for qualities which are really attributable to other components in the system. I’m constantly surprised out how many ‘audiophiles’ claim they know all about music but don’t listen to live music (especially non-amplified music) Real music is not fuzzy and warm it is alive and vibrant with attack and resonant energy. ‘Warmth’ is really a subjective distortion present in most tube electronics. For this reason I would also offer that the ‘tube aficionados’ may not care for the SL-1 as much as other units because it lacks the ‘tube sound’, which is a distortion of sorts, albeit , a euphonic one. It is difficult to assemble a system that has true similarity to live music. You usually get an imbalance one way or the other because in the audiophile’s quest for perfection they wrongly think that by combining different equipment with different strength’s and weaknesses) they can ‘blend’ their system to get the perfect sound. Instead they end up with exactly what they assembled: a sort of sonic salad. The Sl-1 leaves no apparent sonic signature; it merely(?) seems to pass on what’s fed to it unadulterated.
Ken Stevens’s motto for CAT is “technology serving music” .His products are designed to be faithful to ALL aspects of the music not just some. There are no apparent trade offs in the sound of his equipment. CAT equipment will reveal the rest of your system for all of its attendant strengths and weaknesses.
If you value the sound of true, live music, you owe the SL1 and other CAT products a careful audition. They take the concept of transparency to new levels yet preserve the vital harmonic detail and low level musical information that SE designs are renown for. In the here and now I consider the CAT SL1 to be my reference preamplifier because it honors the music without adding anything of its own (that I can detect). Combined with other similarly transparent components and the effect is startlingly lifelike on good recordings.
90493m? "wrongly" a word? (lol)

I agree the CAT is one of the finest pre's in the world. Ideally, I wish all equip was completely uncolored and undistored. But, none of it is!...including the CAT.
I'll agree it's more true to the source than most anything around. Yet, all gear has some "sound" to it, affecting actual source material. It then becomes a blancing act. And, unfortunately all gear is flawed, and some gear sounds best with others.
If a digital recording can SYNTHETICALLY CONSTRUCT an audio signal to make you believe you're actually hearing the actual analog event, then contructing a great sounding system using "less than perfect gear" can be done by mating pieces that compliment each other..infact people do it every day.
Thanks for the review. Just want to clarify that you are talking about the Signature Mk II, not the relatively newer Ultimate II?
FWIW, as an owner of a CAT SL-1 Signature Mark III, I agree with most of your sonic descriptions of the CAT sound. Can't compare to the Io myself, but I do have friends with great ears and discerning taste that feel the Io Signature is one of the finest components available.
What I know for sure is that in my system the CAT outperforms the Joule Electra LA-150 that I previously had, and that it sounds better than no preamp at all(oh so counter-intuitive!)when used w/my Berning ZH-270 w/volume control. Ken Stevens told me that the change from Mk II to Mk III was a significant improvement with a change in the tube complement a major contributor. Although I haven't heard one yet, the Ultimates are supposed to be yet another step towards nirvana...Cheers,


Good to read yet another person enjoying the CAT SL1 Signature preamp.
Like Spencer (who posted before me) I too own the SL1 Signature Mk 3 version. Simply love it! I have never heard the Mk 2 version myself but my conversation w/ Ken Stevens also revealed the same info that Spencer has already posted. So, time & money permitting, I highly encourage you to upgrade the Mk2 to the Mk3. The upgrade should blow your mind!

The Ultimate is supposed to be another step up: from my conversation w/ Ken, the focus in the Ultimate is the power supply (my, what a surprise!) & getting the timral accuracy more right/more true.

Enjoy this preamp - it is a special piece! Yes, there are many people looking for some "colour" in their music thus, do not take well to the CAT.
I also own a CAT Signature Mk III (I purchased it recently). This preamp is very neutral and rather unforgiving with regard to faults, either in the upstream components or in the recording. What it doesn't do is giving that slight creamy and warmish treble like the older Conrad-Johnson preamps. That could be a drawback for some. Is it possible btw to get a more warm treble by changing tubes? Could you please give some recommendations?

90493m, I rolled in tubes into my CAT Sig and this was a very nice improvement. In the phono stage I now use NOS GE smooth plates.Another improvement was when I replaced the stock loading plugs with WBT plugs with Vishays. You may want to try these mods.
I do agree that the CAT is simply a great pre-amp.