Biasing the Power Tubes

As with all power amplifiers that are not self-biasing, hand biasing the twelve power tubes is essential for optimal performance. Jadis recommends that you bias the power tubes anywhere between 4 and 5 volts. Pierre has even experimented with biasing to 6 and higher.

Choosing the right bias for your musical taste is essential to getting the best from the DA-7. In my experience, the higher the bias, the richer the sound. But higher bias also means that tubes run hotter and burn out faster. It can also produce sound overly rich and full, to they extent that the amp begins to sound too sweet, warm, thick, or even syrupy (depending upon your choice of tubes).

It would be very nice if Jadis had made biasing the DA-7's twelve power tubes as simple as adjusting twelve individual settings on the top of the amp and reading the results via a built-in gauge. No such luck. Instead, Jadis' diminutive bias adjustment screws are located inside the amp. You must turn off the amp, remove the protective tube cage on top, turn the amp on its side, remove the 9 screws that hold the bottom plate in place and get the plate out of the way before the bias adjustments become visible.

Once you turn the amp over, expose the adjustment screws, and turn the amp back on until it stabilizes, you must work with four adjustment screws, one for each row of three tubes, rather than twelve screws, one for each tube. Jadis forces you to bias an entire row of three tubes at a time. And while the screws are easy to turn, the tiniest movement can make a big difference in bias.

Given that no two power tubes measure exactly alike, and that bias requires readjustment as tubes age (differently), you must bias the three tubes in a given row to an average level, and recalibrate them every three or four months. To facilitate the process, you will find yourself mapping out the twelve tubes on a sheet of paper, writing down initial bias levels, and adjusting from there.

If you encounter a marked disparity in bias levels in a particular row of three tubes, you must then begin to swap tubes from row to row until the bias range in a particular row is as close as your particular assortment of twelve tubes allows. Assuming you don't burn a hand or drop a tube in the process, getting it right can be fun. It's a bit like a treasure hunt, and ideal for compulsive-obsessive personalities.

It's an especial joy when you discover that the bias of an individual tube is to some extent dependent upon the bias of the other two tubes in its row. When you move a tube that measures 5.3 volt to another row, it may suddenly measure 4.6. Hence what initially looks like a good move may not prove efficacious.

Moving power tubes between sockets and rows is not as intellectually challenging as playing chess, but it does require attention and patience. Much experimentation is required to get your twelve tubes positioned optimally. You may even have to purchase new tubes after you discover that eight tubes are easily adjustable while the four others variously measure much higher or much lower than the others. This becomes more of an issue as tubes age.

Operating a voltmeter (I use a Radio Shack) to measure the bias is easy. You put one lead on the chassis, another on the end of one of the twelve fuses (one for each power tube) easily accessible inside the amp.

Warning. Turning the bias screws is fraught with danger. Brush against the wrong bit of metal with a metal screwdriver and you may be shocked blue by 500 Volts. This may help cure your schizophrenia, but at the cost of the hair on your head or, if you don't have any . . . let's not go there.

The trick is to use a plastic screwdriver to adjust bias. Touch the wrong thing, and no harm is done.

Not so fast. Finding a plastic screwdriver in this day and age may require another little treasure hunt. It seems Radio Shack no longer stocks plastic screwdrivers. Nor do major automotive tool distributors (at least in N. California).

I spent an entire afternoon searching for a plastic screwdriver. I went to carpet stores, auto parts stores, a locksmith, hardware stores, you name it. I tried everything short of driving 45 minutes each way to a computer chain outlet that couldn't tell you what they stocked when you called them on the phone.

Finally, a local locksmith suggested I check out “the old guy in the TV repair shop across the street who keeps irregular hours.” Inside a virtual museum of television history, open for 60 years and stocked with more antiquated TV consoles than I wish to recount, stood a man well into his 80s who boasts that he still works 12 hours a day. Behind him, on his tool display, hung six long Zenith TV adjustment screwdrivers in their original packaging. One had a zip code for the Zenith address; one other was manufactured before zip codes came on the scene. I bought one of each size available. One fit the Jadis. I am still alive to tell the tale.

Models and Distribution

I briefly discussed the Jadis amplifier line with Pierre Gabriel. In his estimation, the next model up in quality from the DA-7 Luxe is the JA-30 30W Class A monoblocks. These also cost $10,500/pair. 30W pure class A usually sounds more powerful than 30W A/B, but it's still 30W.

Then come the JA-80 80W Class A monoblocks, which are very different animals; rather than using a board, they are exclusively hard-wired and employ Jadis' proprietary triple charge technology for even better sound. Thanks to dollar devaluation, they cost $18,500/pair US. I didn't even ask the price of the 200W monoblocks that many favor.

Pierre also extolled the virtues of the Jadis DA-60 INOX-LUXE, a 60W per channel, Class A, auto bias, triple charge technology integrated amp that costs $10,500. I quote: “For an integrated, this is our ‘killer product.” I've put in my request for a future review.

As of this writing, Brooks Burdan Ltd. in Southern California has become the first in-state distributor of Jadis products. Four more U.S. dealers should be in place by the summer.

Authorized repairs and upgrades for older Jadis units in the United States are available from Ron Cox in Colorado (970-882-2530). Like Brooks Burdan, who carried Jadis for many years, Ron knows Jadis backwards and forwards and makes all repairs with Jadis parts. People on the East Coast can work with Jadis' other knowledgeable authorized repair/upgrade person, Avis Brand (516-671-8310).

Internal Wiring

When I received my used Defy 7 Mk. II, Scot Markwell informed me that the wire to the speaker outputs, which runs much of the width of the chassis, had been upgraded to a Siltech silver harness. Scot explained that while Jadis stock wire was good, it has a soft, overtly romantic presentation that lacked tight focus and detail. The Siltech silver harness, in his opinion, made the presentation far more accurate and realistic.

Even though Pierre Gabriel states that Jadis' present choice of internal wire is quite good, he offers a similar upgrade to the DA-7 using his own proprietary cabling. The upgrade can be performed on both the speaker outputs and the preamp (source) inputs. This is a Jadis-sanctioned upgrade. If anyone contacts Jadis in France requesting an internal wire upgrade, they are directed to Pierre who performs the service and installs his own cable.

Pierre explains that manufacturing his cable is far more complicated than simply removing silver wire from a roll and putting a shield around it. There are a large number of time-consuming steps involved.

My DA-7 came equipped with Pierre's cable mod to the speaker outputs. While I have never heard the amp without the upgrade, I have every reason to accept what Scot and Pierre claim that the speaker output cable upgrade accomplishes. I do know for certain, after much experimentation with hook-up wire in my former Bruce Moore Companion III preamp and Michael Green Chameleon III speakers, that choice of hook-up wire makes a major difference in sound quality and resolution. Ask Mike Farnsworth of Talon Audio, who not only changed the hook-up wire in the Khorus X, but also its braiding configuration. I therefore have every reason to recommend the upgrade.

I look forward to the day when Pierre has enough extra hook-up cable available to send me his upgrade cable for the inputs. He claims this will result in a considerably more detailed presentation. This will be all for the better. While the DA-7's resolution tops what I heard through the Defy 7 Mk. II, I have heard more throatiness on Terry Evans' voice when listening through good solid-state amplification. My hunch is that the change of wire to the DA-7 inputs will greatly increase resolution.

The Sound

The Jadis DA-7 Luxe is among the best sounding amps I have yet auditioned in my home. I would not have devoted close to 3400 words (so far) to discussing how to get the ultimate sound from this amplifier if I did not find the effort worth it.

Last night I sat in rapt silence listening to the entire ECM disc of Chants, Hymns and Dances. The disc features improvisations on music by Gurdjieff and Tsabropoulos performed by Anja Lechner on cello and Vassilis Tsabropoulos on piano. The team is beautifully recorded, flattered by an extremely spacious, resonant acoustic of the kind heard on so many ECM recordings produced by Manfred Eicher.

With many of the amplifiers, speakers, and cabling I've auditioned, a lack of ultimate transparency encapsulates voices and instruments recorded in a resonant acoustic in a somewhat gray, whooish halo. No such issue listening to Chants, Hymns and Dances with the Jadis DA-7 equipped with Pierre Gabriel's preferred tube complement. There's a great deal of clarity and detail on top, accompanied by an extremely realistic sense of listening to two musicians situated in a large resonant space. The effect, given the trance-like nature of the music, is mesmerizing.

Listening to these artists' improvisations on Gurdjieff's music through the DA-7 gave me as direct a connection to the soul of music as I've experienced in my years of sonic exploration. It's as though all those metal boxes and wires finally got out of the way, leaving me and the musicians alone in the room.

I of course auditioned two of my stand-bys, the opening of Rachmaninoff's Symphonic Dances (Reference Recordings) and Canteloube's Songs of the Auvergne as performed by Karina Gauvin and a chamber ensemble (CBC Records). With the GE 5751 JANs in the transmission stage, the sound is very crisp, full, and transparent. Bass is extremely tight, piccolos sing, the triangle glistens.

In my extremely live space, minimally treated due to the spousal acceptance factor, the GE 5751 JANs give highs a bright, slightly silvery quality (similar to what I heard in far greater abundance from the Parasound Halo JC 1 monoblocks) that some may find objectionable. There's a similar brightness to David's tenor voice when he practices his Church music in our dining room. For such listeners, the GE 5-Star 5571/7025 combo in the transmission stage, or even a GE 5-Star 5751/GE 5751 JAN combo, may prove more enjoyable.

At first I thought that bass sounded less full using four GE 5751 JANs rather than either tube combo mentioned above. This, I believe, is due in part to the speed of the GE 5751 JANs. The more romantic presentation of the 5-Star tubes adds a modicum of extra resonance to drums, double basses, and even cellos that is not always heard in live performance. The 5-Stars also soften the top a bit, so that the initial attack is not as fierce, and bathes the presentation in a most wonderful, romantic glow. It may not be exactly lifelike, but it sounds positively delicious.

While all three tube choices suggested above conveyed the complexity of Gauvin's voice, the GE JANs made the sharp leading edge of the tone more apparent. The 5-Star combo put more emphasis on the sound beneath the edge. Some might say that the 5-Star combo is less detailed, softer, and more forgiving. But it's also less crisp and transparent.

When it comes to truthfulness of presentation, we can only speak with certainty if we are intimately familiar with the acoustic environment in which a performance is recorded. All the tube choices offered so far are extremely satisfying musically. Choice will ultimately depend upon associated equipment, cabling, room configuration, and acoustics.

Listening to excerpts from the recent Telarc hybrid SACD release of Beethoven's Symphony No. 9 with Donald Runnicles conducting the Atlanta Symphony proved another rewarding experience. (I played the recording in two-channel mode using the Theta Gen. VIII). Using the 5-Star combo in the DA-7, I played the final "Ode to Joy" to nine attendees at our recent potluck. It was so gratifying to watch everyone sitting with rapt attention.

Although a number of listeners commented on muddiness in the upper bass - a situation somewhat room dependent and far less noticeable with all GE 5751 JANs in place - I was most struck by the clarity and focus of voices and instruments. Even at loud volume, with instruments, soloists, and chorus going full blast, the DA-7 transmits information with enviable clarity, offering promise of energy to spare. And it sounds so beautiful!

As I reread this report, I wonder if some readers will somehow equate "beauty" with softness. Please don't. The slam on drums in Terry Evans' great Blues No More (Audioquest/JVC-XRCD), the sharpness of attack on the drums edge, the sizzle of the cymbals - all are as fast and realistic as it gets. If I were to distinguish between the Jadis DA-7 Luxe's speed of attack and that of the killer Parasound Halo JC-1 monoblocks, I would say, to use an analogy, the Jadis might leave you or your partner wanting more, while the Parasound's aggressiveness might be best described as "Slam, bam, thank you ma'am." A chacun son gout.

I have just revisited a marvelous, transportive recording of  Himalayan singing bowls, Deuter's Tibet - Nada Himalaya 2 on New  Earth Records. I first auditioned this disc on the excellent Red  Planet Labs STR201 stereo amp. With the Jadis, the edge of attack on the high-pitched bells is extraordinarily clear. Overtones go on for days, blending into a mesmerizing sonic tapestry. Underneath those high sounds, lower gongs judiciously struck in the background extend way beyond and
above the speakers. Yes, it may be a sonically compromised Redbook CD, lacking the resolution of DVD-A and SACD. But the special qualities of these bells, which have been used for meditation and spiritual practice in India, Nepal, and Tibet for thousands of years, comes through virtually undiminished with Jadis amplification.

Diana Krall's by now Verve classic When I Look in Your Eyes presented a wonderful smoky sultriness with the GE 5-Star 5751/7025 combo. Using all GE 5751 JANs revealed more of the artificially miked sound around Krall's voice, and rendered accompaniment far more crisp and present. Both presentations were delicious in their own way. The combo of GE 5-Star 5751 and GE 5751 JAN, which I'm still experimenting with, may ultimately prove the most satisfying of the lot.

I guess I'm not finished with tube rolling after all.

Conclusions

The Jadis DA-7 Luxe is a wonderful-sounding amp. Its wealth of sonic beauty, openness, air, and power are matched by a frequency extension and sense of control often absent from tube gear. Offering the dual advantages of cooler, less power-consuming Class A/B operation, the Jadis DA-7 Luxe is a must-audition for anyone desiring hour after hour of gratifying listening.


- Jason Victor Serinus -


REFERENCE SYSTEM

Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII DAC/Preamp
Theta Carmen II transport (on loan from Theta)

Amplification
Jadis DA-7 Luxe

Loudspeakers
Talon Khorus X speakers MK. II (with latest modifications and Bybee filters on woofers and tweeters)

Cabling
Nordost Valhalla single-ended and balanced interconnects and balanced digital interconnects
Nordost Valhalla bi-wired speaker cable
Nordost Silver Shadow digital interconnect for DVD-V
Nordost Valhalla Power Cables
Elrod EPS-2 Signature

Also on hand and sometimes used:
Interconnects: WireWorld Gold Eclipse 5 and Gold Starlight 5 digital, Harmonic Tech Magic One, Acoustic Zen Silver Reference II balanced, and Nirvana BNC-terminated digital.
Power cables: Elrod EPS Signature 2 and 3 plus EPS 1, 2, and 3; WireWorld Silver Electra 5, PS Audio X-treme Statement, Harmonic Tech, and AudioPrism SuperNatural S2.

Accessories
PS Audio P600 Power Plant power synthesizer with MultiWave II
ExactPower EP15A
PS Audio Ultimate Outlet; PS Audio Power Ports
Ganymede supports in main digital chain and under speakers
Michael Green Deluxe Ultrarack, Basic Racks and Corner Tunes
Michael Green Audiopoints, and Black Diamond Racing Cones elsewhere
Shakti stones on amp, Theta, and transport
Stillpoints ERS EMI/RFI sheets on most components
Bedini Dual Beam Ultraclarifier, Audioprism CD Stoplight,
Marigo Signature Mat for use atop CDs, Ayre demagnetizing CD and the original Sheffield/XLO demagnetizing and break-in CD.

Room Size
25.5' deep, 37' wide opposite the speakers, 21.5' wide in the listening area. Ceilings are 9'2” high with heavy wooden cross-beams. Floors hardwood and carpet. Speakers are totally decoupled from the floor, resting on Ganymede supports and maple.