Jadis Orchestra Reference bias adjustment?

I've had mine for 4 yrs now and sounds the smae as the day I turned it on. I don't know much about biasing. I guess the tubes have 2000 hrs, but as I say they sound like the day i turned it on. btw I use the bass and treble tone controls up 98% of the throttle. What I've found the tone controls have basically 2 modes, off/on. Only at 90% open do the tones open up, at 95% open there is some slight notice. At 98% is the only way I like it. I love dynamics, and anything less is not acceptable. Also at mid open on the tone the amp sounds very flat and lifeless.
So i guess if you bias from the inside, you get the same effect as pushing the tone controls up to 98% open. Only at 100% do i gut a hum from the amp. btw I lsiten at low volume, 1/4th to 1/3 vol open. After 1/3 I get much less stability /dynamics from the amp. Maybe the speakers are too much a load against the currect for the amp. The speakers are rated 87db. . But still, at 1/3 vol open, i get plenty of music to fill my 30X40(with open hall ways on everyside) cathedral ceiling room. The music carries throughout the entire house. So maybe with low vol I use the tubes will get a longer life. btw Pierre mentioned the Jadis stock tubes are quite expensive, so replacing will be a major cost. Which i have no plans to do for yrs to come.

First, I'd like to say that I cannot recommend my good friend Pierre Gabriel highly enough. We are most fortunate to have him as the North American distributor of Jadis. He is a fantastic person.

Pierre, PLEASE correct me if anything I say here is wrong...

Now, excuse my naivete, but if someone would show my how to post a picture here on Audiogon (do I just include a link to my photobucket.com album?), I can include a photo or two of the resistor that needs to be measured across during the JOR biasing procedure. Robert (mares-mares) lives in Thailand, the document I have is too large to be e - mailed, and I don't want him to have to wait for the mail to reach him there if we can do it simply in this thread.

The picture solves what is the most tricky part when you are inside the amplifier - finding that resistor. The potentiometers are obvious. You simply set the bias to a value between 95 and 120 mV (110 mV being the ideal setting).

I also find there is a lot of confusion as to the requirement of using two multimeters. While I have always used two, doing so with one would be just as efficacious. You are simply trying to make sure that each of the two tubes in the channel stay at 110 mV, as adjusting one could "potentially" throw the value of the other off. I must say that in practice, I have not noticed this being the case (though it was with my Granite 861 amps, but they were super easy to bias as everything was external).

Once you see where the resistor is, the DIFFICULT step of the whole thing becomes actually reassembling the JOR. In fact, my recommendation is to drill additional holes (there's already a lot of them there anyway) in the bottom plate while you have it off that line up with accessing the resistors and pots for each tube. That way, the entire procedure would become a simple no muss, no fuss procedure that would probably be done in about 3 minutes.

As far as time periods go, I think that biasing the amp every year would be good. For someone rolling the 12AX7 tubes, which Roberts wants to do, the difference in gain of the different 12AX7 (and 5751) variants, could potentially alter the bias settings (Pierre could answer this one as I no longer have my JOR to see if it does or does not). But, the type of output tube itself is a big consideration. The Ei KT90 tubes that came with the JOR for a long time are the most rugged, but are not very good sounding. Pierre and I both like JJ E34L and KT88 tubes best in terms of sonics. In my JOR, the E34L produced the BEST midrange I've ever encountered anywhere, though the KT88 will provide more low end and a bit more power. I'll add that I'd been using the new JJ KT77 in my DA60 for its combination of low end and midrange, though since Saturday I've been running the E34L, and am quite happy.

Until I got a tube tester, my JOR sounded fine, other than having to goose up one tube like crazy. It turned out that KT90 tube was shorted (caused no damage to the amp or my speakers), but getting it right sure provided a lot of peace of mind.

Joe,

Thanks again for your posting at Audiogon.

Like you say, a picture is worth a thousand words, and I wonder, if perhaps you could email me a few JPGs indicating the two points, where I have to put the black and red probes of my multimeter.

I think, I will manage to unscrew the bottom part, and sides of my JOR and put it back together.
The location of the bias potentiometers are obvious
I guess, and if I know what the values are (110mv), adjusting the bias should be no big problem.

Basically what I don't know is, where I have to put the black and red probes of my multimeter.

I also don't know, if the value of 110mV stays the same for KT90, KT88, KT77 and EL34 tubes, or if the value changes accordingly, and if it does, what the values for each kind of tubes are.

Perhaps changing the driver tubes, lets say from 12ax7 to
5751 or within different 12AX7s affects the bias settings
as well. I don't know.

Unfortunately I am not living in Canada or the US, otherwise I could ask Pierre Gabriel

The dealer here in Thailand has told me, the JOR has auto-bias, but obviously, it has a fixed bias setting. So, the local dealer seems not to be of great help in this case.

Thanks again for your help.

Best regards,

Robert

Trelja what label 88 are you usig? I bought a quad of Electro Harmonix 88 (EH88) and sounded like c**p. Seems not all tubes are the same. I may try the JJ77's I've heard good things. Or JJ88's, or both. Keep one sell the other.

Robert, I sent you a few photos, illustrating the respective resistor. Let me know if it's not obvious. You just do this for each tube... Once you get the hang of it, you can almost do it in your sleep. In fact, I had my daughter do it for the pictures - she was 12 years old at the time.

110 mV is applicable for whatever output tube you are using in the JOR. Please note, you cannot use 6L6 (5881/KT66) variants. If you can (or, Pierre), please let us know if your experience in rolling the 12AX7/5751 drivers impacts the bias settings ala the differences in gain from manufacturer to manufacturer. Unfortunately, your dealer in Thailand is incorrect in his assertion that the amplifier is autobias. It is not fixed bias, either. As you know, the bias is set using the potentiometers...

Paul, I'm using JJ KT88. This is the KT88 that Jadis sources as well. I believe they say they are special issue for Jadis, but I'm not willing to spend that kind of price premium. The EL34 tubes I use are also JJ. I'm not a fan of Russian tubes in most instances. The Chinese Shuguang/Valve Art/Penta KT88 have a lot of fans right now, and Kevin Hayes is even using them as the OEM tubes in the VAC equipment, which says a lot to anyone who is lucky enough to know Kevin. The KT77 would appeal to someone trying to split the KT88/E34L line, though in the JOR they may give up some power to the KT88 - I don't have a JOR around these days to find out.

Interestingly enough, we had a 12AX7 tube shootout at my home on Saturday morning, and the Chinese Shuguang 12AX7 came in third place out of a pretty impressive lot of six variants. I know that Pierre really hates the Shuguang 12AX7, but Jadis France and I are pretty high on it. At any rate, it's nice to see a $6 new production tube fare better than some of the most vaunted NOS 12AX7 varieties.