Let me start this Review off with thanks to  George Vatchnadze the owner of Kyomi Audio who has afforded me the opportunity to experience both the Convergent Audio Technology JL2 Signature Mk 2 and the SL-1 Legend preamplifier by Ken Stevens. However, this review is for the CAT SL 1 Legend.


First off, a little background information. This audition took place at Keith Perry's home. I was joined by George Vatchnadze, Donald Smith, the owner of Sound Design Labs, Keith Perry and Mike Wright. Keith's system consists of the ARC VT 100 MKII amp with KT 120 output tubes, the ARC LS2B MKII Line Stage, the ARC PH 5 Phono Pre-Amp, the ARC REF CD 7 CD player, Well-Tempered Classic Turntable with a Van Den Hul Frog Cartridge, Vandersteen 5 Speakers, Cables: Dynamic Design (DD) White on the Turntable and Phono to Line Stage. Sound Design Labs (SDL) HPC 4 True Balanced Cables on the CD Player to Line Stage and Line Stage to amp, SDL Speaker Cables with 2 Joule Cases, one per side with (DD) and (SDL) Power Cords. 


We were unable to get the CD player to work and therefore all listening was done with the Well-Tempered Classic Turntable and Van Den Hul Frog Cartridge.

The model SL1 Legend is the top-line preamplifier from the American Convergent Audio Technology company. There are certain significant differences to their Renaissance model. Here we have two separate 46-position shunts with lots of soldered resistors to create ladder-type volume controls. There are two pots, one for the left and right channel rather than a joint stereo control plus balance as in the Renaissance. For the Legend Ken Stevens uses very expensive Rubycon Black Gate capacitors (x 22 more expensive than other high-quality options) which feature extremely solid housings to also make them far heavier than most the competition. The circuit board material was G200 before, now it is Teflon. A transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction.A varying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotive force (emf) or voltage in the secondary winding. Making use of Faraday's Law in conjunction with high magnetic permeability core properties, transformers can thus be designed to efficiently change AC voltages from one voltage level to another within power networks.

The Audio Research LS2B MKII Line Stage, and the Audio Research PH 5 Phono Pre-Amp were no match for the CAT SL 1 Legend with phono. The Legend has one of the best phono stages I've heard and clearly the best integrated unit. Its sound was lustrous, luxuriant but also precise. The CAT offered much better bass control and a more vibrant treble than the Audio Research PH 5 external phono preamp. The line stage offers an amazing precision and the phono stage enriches the sound which was fuller and more emotional than the Audio Research LS2B MKII Line Stage, and the Audio Research PH 5 Phono Pre-Amp. In addition, the Legend is also compatible with both MM and MC cartridges. Both the line stage and the phono stage are based on tubes – two 6922 inputs, two 12AX7 and a single 6922 in the output.

The Legend's phono stage input sports a special low-gain step-up transformer that in conjunction with an MM stage delivers 58dB of gain. The transformer can be set to an additional 6dB of gain but this is recommended only for cartridges whose internal impedance is below 10 ohms. Because of its low gain, the transformer's response is much flatter than others, deviating less than 0.02dB from 20Hz to 20kHz. The whole circuit board is filled with polypropylene capacitors. The separate power supply enclosure is built up of steel plates. It connects to the head unit with a very stiff umbilical and moving and installing the Legend isn't easy. Inside the PSU are huge EI transformer and Black Gate capacitors. 


As good as Audio Research Corp.is, Convergent Audio Technology is in whole different league. In my opinion, it is one of the finest one box Pre-Amps in the Market place, Highly Recommended!!!!!!

By Michael Miguest

By Michael Miguest

 
The 6900 is considered by many to be a rugged version of the 5687 or a Super 5687 as some call it. The 6900 tube was originally developed, circa 1954, for a US Air Force project by the Bendix Corporation of Red Bank, New Jersey. It was in fact used in Pulse applications in the USA's Intercontinental Ballistic Missles, as well as in aircraft and other military applications. Whether the 6900 was actually a 5687 made extremely durable & dependable or whether it was developed from scratch and just happened to come close to the 5687's specs is a subject of debate.

Because it's intended purpose of use, the 6900 needed to be extremely reliable and some of the prime prerequisites were freedom from early failures, long average service life and uniform operating characteristics. All 6900 tubes were subjected to a 45 hour break-in under the various overload, vibration & shock conditions, they were likely to encounter in service. Thus each and every 6900 was tested for it's pulse capabilities under maximum grid-drive and duty-cycle conditions.

This necessitated special materials & manufacturing technics to be employed. The 6900 is constructed from Nonex glass. This causes the 6900 to be quite heavy. It easily weighs as much as any other two 9-pin types together would! It also uses a Tungsten stem seal construction like many of the high-powered transmitting tubes do. The 3 spacers are made from ceramic. Each of these ceramic spacers has the equivalent thickness of about 4 of the typical spacers used in other 9-pin tubes, stacked together. Also the use of ceramic spacers eliminated one of the common sources of tube failure, which is the evolution of gas from other less costly materials such as mica which is commonly used for spacers. Moreover the ceramic spacers along with the use of of multi-pillar supports locked together via 12 welded eyelets, contribute to a sturdier structure. Special alloy snubbers, which maintain their position, retain their spring properties at high temperatures, resulting in a structure resistant to shock accelerations as high as 500Gs.


A friend of mine recently purchased a pair to replace the Phillips 5687's in his AMR-77 phono preamp and invited me over to hear them. This initial listening session had me agreeing with Peter Qvortrup/Audio Note UK who said "The Bendix 6900, I know this is a popular tube with many, but I have to say I find it quite poor sounding, heavy and bright at the same time".


My friend agreed with my initial assessment and several days later invited me back over telling me he had discovered that he had crossed his left and right channel wires in his system. I brought 88 Basie Street by Count Basie and Soft Lights and Sweet Music by Scott Hamilton and Gerry Mulligan. We listened to Bluesville and Nobelesse. We also listened to a 45 RPM Reference Recording, Dance of the Macabre. I found this session sounded only a little better than before but was in no way jaw dropping. The hyperbole that the majority of  so-called audiophiles bestow on this tube wasn't demonstrated to me in his system in no shape, form, or fashion. 


I think its very important that the readers here understand that I have experienced this system with the stock Phillip's 5687 tubes many times before his purchase of the Bendix 6900 tubes and thoroughly enjoyed the musical presentation. My friend was most impressed with the added weight of the musical presentation that the 6900's brought to the table. However, I found it to be dark and heavy which mitigated a lively presentation, which I prefer, and subsequently a diminished magical quality which I experienced from his stock 5687's.


Too often in this hobby, hyperbole, specifications, and price rule the day as opposed to performance. In my opinion, the Bendix 6900's are "Overpriced", "Overrated", and with regard to the musical presentation, "Under Performed".