Jadis OR bias value for Mullard RL34 and KT88 help


I just swapped my Gold Lion (reissue) KT88 tubes for Mullard EL34's and was vwery surprised that the volume was so much lower. I checked the bias and found it to be less than 10mv while the KT88's had been biased at 110mv.
I rebiased the EL34's up to 90mv and the volume increased to what seemed to be "normal".
I am looking for the correct voltage to bias the new EL34 to in a Jadis Orchestra Reference.
Any help is appreciated.
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Showing 8 responses by mechans

It is too bad that you can't e-mail other Audiogon members anymore. My old friend Trelja could tell you about biasing EL-34s in a Jadis Orchestra Reference. BTW he did the same thing but swapped out the then standard KT-90s and loved the improvement.
I bought a used DA-60 with a mixed bunch of shot EL-34s in it and went the opposite way and put in the GL KT-88s which I though were much much better. It is time to retube and since I like a "big" sound I think I will try the GL KT-77s.
Joe do you still have the same e-mail I have been meaning to get in touch with you and perhaps visit. I have a lot to tell you about. My old e-mail will work if you want to try first. You know Micheal/Sufentil reached out a while back but I was terribly remiss in not answering, again a story with that. I seem have gotten disconnected from the PAAG. I know you aren't following them but If I had been in touch I would have made the New York Show.... I really should have gone to meet the industry people, I would love to get involved on that level.
The reissue Tung Sols are a very good current production 12AX7. I find them clean, clear with a strong signal that is full range capable, they rarely call attention to themselves.
Unfortunately the NOS supply of 12AX7s has dwindled and what's left don't look so good or are very expensive indeed. You may have more luck with 5751s which won't give you all of the gain you might desire but have exciting tonal qualities. They have been discussed ad-infinitum, so I won't say more than that you might want to investigate that option. I don't recall hearing them in the Orchestra but Trelja and I have DA-60s (unless he parted with his,) where they are fabulous 12AX7 subs. I will make one suggection. The most bass emphatic 5751 that we encountered was probably the GE Triple Mica Grey plates. They are not as detailed or as good in general as the 5751 black plate tubes tend to be, but will provide as much bass as any will, if you should see a continuing need for it.
The Tung Sols are competent tubes that do their job in a somewhat understated manner in my experience, they have very good tonal balance. I would be hard pressed to say they are better than the Shuguangs. The Shuguangs have much better treble extension and are indeed cleaner than the Tung Sols now than you have got me comparing the tubes.
I was thinking that his choice for 12AX7 was a good one that really shouldn't have any negative impact on the overall sonics he is looking for.
Joe what would you say provide the most bass in that family of tubes? I remember when we were trying to buy 5751s and you telling me that the Grey Plates, while not your ultimate choice, had "thunderous bass". I found your description to be spot on, and never forgot it.
Indeed I was going to tell you what Joe did. The JJ E34L is a different tube, I think IIRC that the height is slightly longer than the regular JJ EL-34. The other cool thing is that the E34L comes in colors. Trelja and I preferred the Blue glass. I am not sure but I think the color helped with heat dissipation.
Unlike Trelja I never noticed the loss of bass or low end extension relative to other EL-34s. It possibly true and Joe is rarely wrong about all things audio. I haven't had the matched octets necesarry to make such a comparison in a long time.
I am just wondering outloud, if you might want to try the Gold Lion Reissue KT-77 at some point. When I get my equipment back, I was thinking about putting the KT-77s in my DA-60. I will report my findings should I endevor to make the switch, but my amp is not a JOR, so it may not be very useful to you.
I have never rebiased the amp because it has an autobias circuit built in, and I am uncertain if I can overide the autobias, and bias the amp manually. It would be a PITA in any event the amp is pretty heavy and I am not young anymore.
The fuse ratings are typically on the fuse cover, and then again on the fuse. If all else fails see if you can download a users manual from Jadis. The other sources are probably commercial and would want a fee. Joe (Trelja might pop bback in to help you also. If not spontaneous start a new post.
Sure Joe, you know what I have a rarely used one that I don't need to protect so carefully, I will tell you here try [email protected] I can only access it occasionally so forgive me for a slight delay. Once there I will update you on my current addy. Thanks for asking it has been a while my old friend!
Thanks for the link Sumonkabir those tubes look cool and the sales pitch seems plausible even if we can't confirm that it is meaniingful of true. The other possibility that I mentioned but haven't done is to get Gold Lion re-issue KT-77s which are a somewhat higher powered EL 34. I don't know if the bias needs to be changed but it shouldn't be majorly different than an EL-34. To be safe and certain just get a truly matched quad from a good vendor. If not buying from Trelja who on occasion sells some Chinese tubes get the from McShane Design over on Audio Asylum or by search. He really matches his tubes and trys every one of them to avoid sudden infant tube deaths.
Another tube to consider is theso called fat bottle Electro Harmonix 6CA7 which are equivalent to an EL 34 and are direct subs. They put out a really big sound although th Psvane tubes look a lot like the dimension wise. We talked earlier in the thread about the input tubes.