Check the archives for posts on the JOR by Trelja, he had an offer to send out an instruction sheet on how to do the biasing, and he may have deescribed the process in the posts as well.
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Northstar (firstname.lastname@example.org) or http://www.northstarleading.com can fax or e-mail you bias instructions. You will need TWO digital voltmeters to adjust the two trimpots on each output transformer. Since high voltage exposure would result, I suggest that once obtaining the directions (which I could also fax you), that you have a qualified electrical service technician do the work. Good luck, and happy listening,
Apparently, there are somehow inconsistent views about how often the bias on the JOR needs to be adjusted.
While most owners here at Audiogon feel adjustments are necessary every few months, one dealer in Europe says, adjustments are only needed once every 4 -5 years due to the fact, that Jadis only uses selected and well burned in power tubes.
Jadis in France says, the JOR needs no bias adjustments at all, unless power tubes are changed.
How often do you owners adjust your JORs if you dont change output tubes?
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.
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.
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.
Though I must thank Denis for his unbridled kindness, the document I put together when I sold him my JOR was flawed.
It seemed there must have been some confusion in the translation of the biasing instructions into English, and that is what I used to bias the amp. There are 4 potentiometers in the JOR, one for each tube. The instructions I received stated setting one pot of each channel to 110 mV, the other to 0.0 mV. After having this pointed out to me, it was obvious that ALL FOUR tubes should be running at 110 mV.
I'll take full responsibility for the previous errors of my ways. I should have followed up with a confirmation of the instructions with Jadis - France, but I did not. My fault...
Pierre Gabriel, the US /Canada Jadis Distributor must be highly recommended.
Even I live in Asia, he still took the time to speak to me for about an hour on the phone, giving me all kind of information about the JOR and other Jadis amplifiers.
He has great technical inside, and is real fun to talk to. It was a very positive experience, I like to say.
Pierre will talk to you for an hour about the Jadis line. I think he realizes Jadis expects him to make sure their product is understood by newcommers to Jadis. Besides Jadis' exclusive rights to making the finest tube amps may be slightly altered here in the US once Cayin makes its way to the US shores. Thats yrs off, but indeed will one day be competition for Jadis.
I just want to thank everybody: Narrod, Trelja, Maresmares, Springbok10, Menosh for your support and great comments.
Importer / Distributor for Jadis / Pierre Gabriel products Canada / USA.
toll free Canada / USA: 1-877-430-1485
This is a great forum! Thanks to everyone who helped me with my questions and concerns. I have learned a lot, met some nice people on the way, and got all the information I have asked for.
Now I know how to adjust the bias on my JOR. It is actually no big problem, and could be done by anyone in a short time. On my JOR, the bias on all four tubes was still within the specified range, but after adjustments, they are now perfectly biased again.
Hello, maybe it is not the perfect place to address my question, but as a lot of people owning the JOR seem to be here, I give it a try instead of opening a new thread.
So: does anyone compared the Tungsol 6550 reiusse to the SED SV6550C? I use the Tungsol reissue now, for over a year or so, that has replaced JJ KT88's. I'm quite satisfied with them, but some say that the SED SV6550C is one of the finest if not THE finest, so maybe I should give it a try?
Also: we use the JOR with 220mV for the output tubes instead of 110mV. Some expert examined the JOR, and said, that it can be a problem, the transformators won't be injured or whatsoever, and the sound will be more lively and dynamic and it is. The only problem that can happen is that the output tubes will last shorter. So we use it this way for a year and a half now, and no problem appeared at all. Would be interested in your opinion about it. Of course I DO NOT advise it to anyone to try in his/her JOR. I did it for myself, in my JOR, that I'm responsible for.