Convergent Audio Technology
Ultimate Tube Preamplifier

        There is a fairly strong contingent of Audiophiles who feel the Convergent Audio Technology (CAT) Ultimate is the best tube preamplifier you can buy. Of course, high-end audio is all about personal preference, so I don’t think we could all agree that one single product is better than all others. Yet, I can think of no other preamplifier that has been more lauded in the press, and owned by more reviewers than the CAT. It is without question one of a very small handful of preamplifiers that are worthy of being called the very best.
        Another unique quality of the CAT preamp has been its staying power. Designer Ken Stevens has kept his preamp in the very top echelon of the category since he introduced it in 1985. No small feat. The latest incarnation is the CAT Ultimate and it continues the tradition of greatness we’ve come to expect from Convergent Audio Technology.
        What does the CAT sound like? Very neutral, I’d say. The piece does not have a strong tendency to either end of the tonal spectrum. It is neither bright, nor warm, offering a tonal balance that remains true to the source. Though there is no mistaking you are listening to a tube preamp, you’ll find no excessive tube coloration here, nor is there brightness or stridency that can be a common trait of the solid-state genre. 
        Over the years, I’ve admired the CAT for its wonderful ability to define sound-space. The CAT offers much more than just the ability to delineate the gross characteristics of depth and width. Though exceptional at each of those, this preamp, more than any other I’ve heard, excels in two areas which help to define minutiae in the stage: 1) the CAT reproduces the space between and around instruments on the stage incredibly well. This characteristic helps to separate and delineate each player on the stage. 2) The Convergent gives dimension to each of the performers, offering a greater insight into the forms making the music. For me, these two finer points make music more enjoyable and involving by offering greater insight into the performance.
        Combine tonal neutrality with state of the art soundstaging and you have one superb preamplifier! My highest recommendation. $6995.00.

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Review by Audio Reference:

 Introduction

There is no longer the need for the music lover to choose between a "musical" and an "accurate" preamplifier. CAT has proven that, when taken to the highest level, these attributes converge, just as the do at a live concert.

CAT's philosophy

Is to design products that neither adds to, nor detracts from the music. They never attempt to cover up a design problem with another problem, nor do they introduce a supposedly complimentary problem to "synergise" with it. Two wrongs don't make a right. Only the eradication of the problem is correct.

The SL1 Ultimate is the product of relentless refinement to the original SL1 introduced in 1985. Every electronic artifact has been identified and eliminated. Rather than attempting to "synergise with badly flawed systems, this preamplifier is designed to allow superior systems reach their fullest potential.

Design Concept

Power Supply

• External power supply chassis lowers noise and allows for much larger transformers
• Initial regulation and noise filtering are all performed in the outboard supply insuring ultra quiet DC power to the main chassis
• Three independent fully regulated filament supplies eliminate the dynamic compression caused by filament to filament crosswalk. (These supplies are also noise filtered).
• Slow filament power up extends tube life greatly.
• Quadruple cascaded audio power supply combines twenty two zero feedback regulators with over thirty energy storage and bypass capacitors for unequalled dynamic life, soundstage precision and musicality.
• Isolation transformers eliminates entry of radio frequency noise through the AC power line

Circuitry

• Pure vacuum tube circuitry
• Extraordinarily quiet, high gain phono amp (Optional) accommodates both high and low output cartridges.
• Speed, openness and transparency without any of the high frequency circuit-induced edginess which slower pre-amps frequently substitute for real speed.
• Very low output impedance reduces sensitivity to cables and load, even into long runs of cable.
• Lowest open loop distortion of any pre-amp yields unforced detail and resolution that must be heard to be believed.
• Low feedback ratios eliminate the aggressiveness of high feedback designs and yet still maintains correct focus.
• Matched output impedance reduces reflections within interconnects, quickly, yielding exquisitely lucid midrange and treble.

Chassis

• Very strong steel chassis with anti-RFI plating ensures hum & RF free operating environment for the circuits.
• Damping material lines both chassis to stop mechanical resonance, which would otherwise modulate the electric fields in the pre amp.
• Mechanical isolation from floor vibrations provided by high loss viscoelastic feet.

Quality

• Exotic low loss circuit board material combines the transparency of hard wiring with low resonant signature and musicality of circuit board designs
• Balance and volume controls are military grade rotary switches with solid silver contacts wired with precision resistors
• CAT manufactured RIAA capacitors use a unique dielectric with several time lower loss than any other dielectric including TFE Teflon
• The best sounding precision resistors are used everywhere for the best resolution and minimum unit to unit variability
• CAT coupling capacitors are made to our specifications and are better than any other audiophile grade capacitor
• CAT audio wire uses ultra pure, soft annealed copper and super low loss insulation
• Rhodium/gold jacks for superior connection
• Silver solder used for best electrical connection
• Custom designed hermetically sealed switches

Convenience

• Front panel-muting switch.
• Automatic mute on turn on and off. Record/normal front panel switch eliminates the non-linear load of the turned off tape deck when in normal and provides uncompromising recording quality when in record.
• Extra set of main output jacks for special audiophile set-ups.
• LOAD jack allows changing MC cartridge loading while listening to music.
• CD and A/V volume control tapers available.

SL1 Ultimate Pre-Amplifier

Specifications (phono stage optional)