Dick Olsher's original review of the JA 200, published in November 1993, hadn't been as sunny. Dick had found the lower midrange "somewhat meager," the sweetness, sheen, and vitality of violin overtones and soprano voices "blunted" and "subdued." Nonetheless, he called the JA 200 "one of the most musically appealing amplifiers money can buy. It's certainly the most impressive high-power tube amp I've heard."
With such praise still in mind, in 2002 I bought a used, considerably less expensive Jadis Defy7 Mk.II stereo amplifier (approximately $6500 when new) made in about 1993, and repeatedly risked electrocution in numerous expletive-laced sessions of tube biasing that also necessitated backbreaking heavy lifting. A glutton for punishment, I eventually upgraded to the Defy7's successor, the DA-7 Luxe (approximately $11,000 when new, discontinued). After changing some of its tubes and internal wiring at the suggestion of Jadis' former North American distributor, I finally caught a glimpse of the Jadis "magic."
In April 2017, at the AXPONA audio show in Chicago, in the room of Kyomi Audio, a Chicago-based dealership run by pianist George Vatchnadze, I heard brand-new Jadis JA200 Mk.II monoblocks ($33,900/pair). Despite their insufficient break-in, I was moved to write: "I was so taken by the sound that all I wanted to do was sit and listen, and then listen some more. And it wasn't just the fabled Jadis midrange that had me in its grip; the bass was also quite good, and the highs divine."
I learned that the JA200 Mk.II is an auto-bias design; remembering how close I had come, years before, to permanent injury, that feature seemed a gift from the gods. In addition, the amp's adjustable output transformer strapping, designed to work with speakers rated from 1 to 16 ohms, suggested that it would mate well with my Wilson Audio Specialties Alexia loudspeakers, whose impedance drops to 2 ohms in the bass region. In his Measurements sidebar to Dick Olsher's review of the original JA 200, Thomas J. Norton had observed that "The Jadis's output impedance was admirably low for a tube amplifier." This, too, indicated that JA200 Mk.IIs might work well with the Alexias, given that amps of lower output impedance have an easier job driving speakers with complex impedance curves.
The power behind the gold (brass, actually) Like the founders of so many other high-end audio companies, French music lover and amateur radio operator André Calmettes began by designing and building an amplifier for his own use. Several friends heard it, and asked him to build copies for them. Demand grew. In 1983, Calmettes and a friend cofounded Jadis.
The new company's first production model, the JA80 push-pull power amp, is still in production, albeit in what Calmettes's son, Jean-Christophe "JC" Calmettes, calls an "evolutionary" form: the JA80 Mk.II. Like all of Jadis's long-standing models, the JA80's basic circuitry and Jadis-made output transformers remain unchanged. The circuits of nearly all Jadis amps share the same basic push-pull design, have the same number of stages, and use only a small amount of negative feedback. The goal is to maintain the Jadis sonic signature throughout the line.
"We wind and pot our transformers ourselves," JC explained when he and Richard Colburn, of Jadis's US distributor, Bluebird Music, visited me in Port Townsend, Washington, to install the JA200 Mk.IIs. "The output transformer is the heart of the amp. Its quality is of significant importance when it comes to speaker matching.
"All stages in our amps are fed by our very strong power supply. We use big transformers and a lot of capacitors to produce the cleanest possible signal. Our super-low output impedance causes our amplifiers to exhibit the same low output impedance of many high-end solid-state amplifiers." Jadis is so confident in their transformers that they come with lifetime warranties.
Because Jadis's website and the JA200's manual are short on technical details, and JC's command of English is limited, I asked Colburn to confirm which parts of Dick Olsher's 1993 technical description of the JA 200 also describe, a quarter-century later, the JA200 Mk.II. Those parts are:
"The heart of any power amp is its power supplythe reservoir of current for the output stage. . . . Jadis did not skimp here in terms of parts quality or reservoir rating. Solid-state bridge rectification is used exclusively, followed by an RC filter network. Filament voltages are regulated, but, as is almost always the case, plate-supply voltages are unregulated.
"Using the two halves of a 12AU7A dual-triode tube, the input/phase-splitter stage comprises a Schmitt cathode-coupled circuit. This clever push-pull stage has rarely been used in audio amps, primarily because it requires two tubes and offers only moderate amplification. It was originally intended for scientific instruments (eg, oscilloscopes) for which extended low-frequency response is desirable. Coupling caps are not required, and hence frequency extension to DC with good balance is easy to achieve with this circuit. The phase splitter is DC-coupled to a driver stage that uses a 12AX7A dual-triode. Thus, the entire front-end of the JA 200 is DC-coupled."
In the JA200 Mk.II, launched in 2016, the power transformer and cathode circuit have been modified to accept Russian-made Tung-Sol KT150 power tubes. The chassis are made of 304L polished stainless steel, and the characteristic Jadis golden plating is brass.
Setup Listening to music in stereo with the JA200 Mk.IIs requires not two but four chassis: each monoblock has its own outboard power supply, attached to the amp proper via a supplied umbilical cord. At the center of the front panel of each of the four boxes comprising a pair of JA200 Mk.IIs is a single power-on light. When the Power switch on the left side of a power supply's front panel is flipped up, the tubes are warmed up to operate at 30% of capacity, and the lights on the amp and its supply glow red. After 1015 minutes, it's okay to turn the switch on the right side of the supply's front panel from Standby to Operate, to run the tubes at full capacity. Doing so turns both indicator lights green. JC told me that it was unnecessary to wait longer to hear all the JA200 Mk.IIs had to offer, but I invariably did. Jadis cautions users to always turn on their preamplifiers before turning on the amps, and to reverse that procedure to turn the amps off. I did as instructed, using the dCS Vivaldi DAC's volume control instead of a preamp.
After we'd unpacked the ampsthey'd already been broken inJC Calmettes removed their tube cages and installed the total of 24 tubes. The review samples each sported 10 KT150 power tubesthe most powerful JC could supply. "When I talk about value with tubes," he said, "a tolerance of 7 to 10% is normal." This helped explain why he told me that the JA200 Mk.II can output 170W, though its manual and the Jadis website specify 160W. Written on each tube's box was a number corresponding to its proper socket in the amp, as indicated in the manual.
I'm outa touch, I'd thought that the bigger Wilsons all had Servo Woofers. Hmm How do they get away without Woofer control ? Of course a Solid State Amp's dampening is mandatory.
ps. there is an Engineering document covering Audio Output Tube spacing, I think the minimum gap is far greater than glass to glass ( which looks like a Submarine Missile Launch arrangement )
... is rather tightly packed, but there are perforations in the chassis between the tubes to promote air flow. https://i1.wp.com/i1190.photobucket.com/albums/z446/sthull/CES13/Part1/CT6A6117.jpg?resize=640%2C427
I'm a tube fan, especially in Microphones used for Studio Recordings of Vocals. Tubes in Pre-Amps are one of my favorite things. Tubes in Amps have never performed well for me, with the ( only ) exception being the Conrad-Johnson MV-45a driving MG2 Maggies with Music Hose MIT750.
The Tune Audio Avaton Horn Loudspeaker gets Tube amplification and is flat out addictive. ( leave your financials in the Safe or you'll kill yourself to own it )
No Servo Woofers ? new Submitted by tonykaz on February 2, 2018 - 1:59pm "I'm outa touch, I'd thought that the bigger Wilsons all had Servo Woofers. Hmm How do they get away without Woofer control ? Of course a Solid State Amp's dampening is mandatory."
The reviewers Wilson Alexia are full range passive (no active bass) but that bass can go as low as .9ohm EPDR, I can't see any tube amp even this one getting the very best out of the Alexia's bass, like a big current pumping solid state could do.
Then you can read between the lines of the reviewer. "the bass was also quite good" "the bass less full" "the double basses that give extra urgency and dread to the symphony's opening were hardly audible through the JA200 Mk.IIs. While I can't confirm that this bass shyness was due to the Alexias' impedance dip down low"
... a pair of the Parasound JC-1 amps. >4kW output into a 1Ω load. https://www.stereophile.com/content/parasound-halo-jc-1-monoblock-power-amplifier-measurements
I had them way, way back in my pre-Stereophile days. Given that I'm reviewing different equipment each month, as well as reviewing recordings and covering audio shows and teaching about opera and art song and covering concerts [see https://classicalvoiceamerica.org/2018/02/03/a-too-emotional-violin-concerto-played-to-the-hilt/ -- I'm really proud of this review] and plays and writing concert previews and..., auditioning extra products is not so easy.
The good news is, the Wilson Audio Alexia 2 loudspeakers, with a nominal impedance of 4 ohms that dips to 2.8 in the bass, demand less of an amplifier. Review and follow-up of those speakers to come.
... of the Wilson Audio Alexia Series 2. Will also need to see the phase angle test results to determine just how severe a load might be presented by that speaker.
Parasound versus Pass Labs makes a fascinating comparison. Both John Curl and Nelson Pass have identified certain (and different) aspects of the amplifier distortion spectrum which each seeks to optimize in order to achieve a specific sound quality. JA should try to arrange a simultaneous video interview with these two designers.
Regarding driving the Jadis amp from the dCS DAC, no compatibility issue is evident based upon the specifications. The Jadis has an input impedance of >100kΩ and an input sensitivity of 910mV. The dCS can drive a load as low as 600Ω (with 10kΩ-100kΩ being recommended) and can be set for a 2V full-scale maximum output - more than enough to supply the specified 910mV.
Without utilizing an upstream preamp, you have NOT heard what these amps are capable of. IME, this is always the case with tube amps...and most ss amps as well! Your Dcs DAC was a very poor choice to drive these amps! Strapping the amps for a 1 ohm load, more than likely not the best solution either...the 4-8 ohm strapping would have been more appropriate. I would strongly suggest a follow-up review; this time with a decent preamp upstream and different strapping. I suspect ( strongly) that your opinion of the bass response and the treble concerns would be ameliorated. Commenting/reviewing mismatched components is not really fair to the component manufacturer under consideration. All IMHO.
a. The choice of strapping was made by the manufacturer and dealer. You may wish to correspond with them. They had the opportunity to request a follow-up review in Manufacturer's Comments, and did not do so.
b. Why is the dCS gear a poor choice to drive these amps and other amps? I have certainly had no problem with any of the SS amps I've reviewed so far. Why are the products mismatched?
FYI, for my next two reviews where a preamp is definitely required, I have been sent a loaner two-piece Lamm preamp. How I'm going to fit it on my rack will be determined shortly.
Ok, you actually brought up a good question...why is the Dcs a poor choice to drive these amps...and not ss amps? I believe it is a poor choice for ALL amps. The Dcs is designed as a DAC...not as a preamp. ( BTW, the ONLY DAC that might qualify SQ wise to drive an amp is the new MSB Select DAC; and as you may know, the Dcs is not in that league at all) A great preamp will have the DRIVE to handle a tube amp...like the Jadis 200Mk2's. The Lamm's you are going to be receiving would certainly qualify in this way. Pair the Lamm's and the Jadis and you would have a much better idea as to what the Jadis can bring to the table. Why are the products mismatched...YOU SHOULD NOT HAVE TO ASK THIS QUESTION!! Pairing a very difficult to drive speaker ( ala WILSON ALEXIA's-- which have a brutal drop in their impedance in the bass) with a tube amp is asking for trouble, IME. You heard what the combo brought about..along with the mismatch of the DAC!! Wake up man...it's horses for courses in our hobby. Would you pair an Apogee Scintilla with a 3 watt flea powered SE amp??? You would IF you do not believe in such a thing as "mismatching'!! --and were inexperienced in the hobby. BTW, the dealer you mention ( who shall remain unnamed) sold a friend of mine some lower powered Jadis amps for his difficult to drive Gamut speakers( which the very same dealer also sold -- and we are NOT talking about cheap speakers here) Knowing full well the size of my friend's room...Do you think this very same dealer is going to get any of my friend's future business?? If, as you say, the manufacturer has not requested a follow-up, they are making a serious mistake. However, considering they are out of country, that may be a reason. Although, i cannot comprehend why their rep in the US is not all over this!!
I have no answers for absolute statements such as "the ONLY DAC that might qualify SQ wise to drive an amp is the new MSB Select DAC; and as you may know, the Dcs is not in that league at all," and "If, as you say, the manufacturer has not requested a follow-up, they are making a serious mistake."
I’m not considering a job as an audio consultant, but I may have to consider the job opening for an audio reviewer. LOL.
BTW, have you actually heard the new MSB Select DAC...doesn’t sound like it, otherwise you would understand why the difference can be stated as an absolute.
Submitted by Jason Victor Serinus on February 6, 2018 - 4:29am "Wilson Audio Alexia 2 loudspeakers, with a nominal impedance of 4 ohms that dips to 2.8 in the bass, demand less of an amplifier."
You had your doubts with this statement also Victor. ""the double basses that give extra urgency and dread to the symphony's opening were hardly audible through the JA200 Mk.IIs. While I can't confirm that this bass shyness was due to the Alexias' impedance dip down low"
Once we've seen the impedance in conjunction with the -phase angle graph in the test, only then we'll see the true EPDR (equivalent peak dissipation resistance) impedance in the bass as seen by the amp, and I will lay money on it, that's it's going to be lower than 2.8ohm
i had a pr of ja80s and later a da60 integrated, both sounded fine but the da60 was one of the most unreliable pieces of gear i ever owned. hopefully the latest jadis are built to go the distance.
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George, I would be willing to bet that your supposition that the Alexia’s drop below 2.8 ohms is going to be spot on! IMO, utilizing the new Jadis 200 Mk2’s with this particular set-up was a recipe for failure from the beginning....too bad that a good amp is not getting the precise and accurate review that it deserves. Perhaps request a follow up with more appropriate ancillary gear...and another reviewer, lol.
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