Jadis Orchestra Reference bias adjustment?

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.

Thanks a lot. I really appreciate all the help. With the pictures and descriptions, it should be easy now.

It’s great to get all the support here at Audiogon

It is obvious that Joe (Trelja) has no limits to the generosity of his time and expertise. When I bought his JOR, he compiled an entire color manual of bias instructions for me. We all appreciate your helpfulness, Joe.