Recently a client of mine brought in a slightly ill Jadis Defy 7 for repair. Having performed the repair in a small number of hours he then suggested that he leave it with me for a while, as it was his opinion that I would find the experience quite enjoyable, and I did...
The unit that I repaired was built in early 1991 and was a dealer demo, so my comments should be construed as applying to units of this vintage as it is my understanding that an improved version is now available.
The amplifier presents an attractive appearance with a large, uncrowded brilliant chrome chassis with three huge transformers set along the rear lip of the chassis. Four banks of three tubes each flank two large custom computer grade capacitors in the center. Two triangles two apexes of which are coincident with the banks of output tubes are formed near the front lip by two triads of small driver tubes.
First off, so that you know where I am coming from, I feel that this is one of, if not the finest stereo basic amplifier I have encountered from a purely sonic standpoint. The design is simply elegant, although slightly marred by some workmanship related issues that I will discuss among the technical issues.
Sonically this amplifier is refined with barely a hint of the fact that it is an ultralinear design - which in many implementations hints strongly of the tetrode/pentode output devices used... This amplifier is clean, with a slightly lean, but very neutral mid-range - the detail, timbre and instrumental textures (when present) are about the best I have heard. Woodwind instruments are reproduced with their full harmonic structure intact and cleanly delineated. Strings separate into their individual instrumental arrangements instead of sounding like a group of homogenized strings or even worse like one giant violin. The overall presentation is warm, balanced with good extension to the frequency extremes, and the bass performance is quite authoritative and well damped - a slight bloat in the lower mid bass that I initially attributed to this amplifier appears to be a room resonance. (Highly likely in my untreated listening environment.) Cymbals are well reproduced with just a hint of dulling on the leading edge and an overall softening - an effect that does not really manifest itself obviously or obtrusively. There is no spitty or sibilant treble here, just smooth, clean and highly listenable. The space between musical notes is "black", that is to say silent, with no overhang or noise present in the silence between notes. This amplifier could rightly be termed a high definition amplifier without any of the negative baggage conveyed by the definition - in that the Defy 7 achieves high definition without subjectively or otherwise shifting the timbre of instruments towards the bright end of the spectrum.
This amplifier does image well and the space between and location of individual instruments is palpable. Depth is as good as my maggies can manage given the CDP-790 which was used a source for this evaluation. Vocals retain their individual nature and the location of the individual vocalists is easily discernable within the soundstage.
A variety of music was used to evaluate the amplifier and as is the case with the very best amplifiers any music was reproduced with aplomb and without exacting a penalty on another type of music. Here follows a list of some of the material used in this review: Mickey Hart's: "Planet Drum", on Rykodisc #RCD10206, Temple Caves (7) for its huge Earth Drum and The Dancing Sorcerer with its Berimbau - a percussive bow like instrument that generates some very interesting percussive sounds; multiple selections from Wynton Marsalis: "Tune In Tomorrow", on Columbia #CK47044; Mercury Living Presence (MLP): Respighi "Ancient Dances and Aires for Lute" #434 303-2 cut #8 Bergamasca; as well as cuts from MLP NOS. 432 009-2 British and American Band Classics, and 434 301-2 Dorati Conducts Copeland - Appalachian Spring, Billy The Kid (Complete!!)
The technical aspects of this amplifier are quite interesting, this design uses 3 pairs of 6550's (CHINESE NOT RECOMMENDED!) per channel in an ultralinear, cathode coupled configuration. The driver circuit per channel utilizes what appears to be a differential amplifier employing a 12AU7 direct coupled to another differential amplifier/phase splitter consisting of a pair of paralleled 12AX7A's for each output phase, which are in turn coupled to the output tubes through individual coupling capacitors. The output stage employs fixed bias, but is not really intended to be adjusted by the typical user as evidenced by the locking adhesive used on the individual pots. One pot is employed for each bank of three output tubes, obviously it would be a good idea to use matched sextets in this amplifier. The output transformers are the largest I have seen anywhere and can be configured to drive 1, 4, 8, and 16 ohm loads by reconfiguring a bunch of jumpers on terminal blocks adjacent to the transformers on the underside of the chassis. Almost all of the circuitry is carried on one high quality fiberglass epoxy p.c. board. The component side faces toward the bottom of the chassis while the sockets are soldered directly to the upward facing trace side of the board. All components were well soldered except for the sockets carrying the phase splitter/cathode follower circuitry (Cathode Followers are bypassed for the US market) where several cold solder joints were encountered as well as two jumper connections under one of the sockets which were not soldered at all. Whoever performed these modifications needs to exercise greater caution in soldering....
I have three real beefs with this amplifier - all of which may have already been rectified. First I am concerned about the fact that the p.c. board and chassis don't line up well - sockets barely clear the chassis because of a rather serious misalignment between the socket locations on the board and on the chassis. The second item concerns the choice of output connector - how about Cardas, Edison - Price or WBT, with the attendant beneficial elimination of several mechanical connections in the process? And finally I think RTV should be relegated to home D.I.Y projects and not the electrolytics in what is afterall a very expensive amplifier.
In closing this is a great amplifier and probably the best I have yet heard. Listening is a pleasure. If you can live with a very large heavy, but attractive amplifier that in many ways represents the state of the art, and can afford an outlay of $3000 or so for a used one then this could be for you....
N.B. The original component failure that resulted in the repair that resulted in this review appears to have been caused by a defective resistor, not anything that Jadis could be held accountable for.
©1998 By Kevin R. Kennedy