Contact Chris at Parts ConneXion in Canada. He recommended the KT120's for my Sonic Frontier Power 2 amp and I am more than satisfied with the sound. He is a good guy to deal with.
25 responses Add your response
I tried contacting Jadis with no response (broken link?), hence I am trying other avenues, even Pierre G. (Canada Jadis Distributor)with no response yet. Checking for possibly any savvy A'goners with the Jadis Defy filament transformer specs/capacity. Thanks Kkurtis for the contact. I will keep trying.
As I have stated in a few other threads....the KT-120 is NOT a drop in replacement for the 6550. The KT-120 draws more heater current per tube. Using it could pose a potential risk to the heater winding in your power transformer and/ or make the transformer run hot. Do contact the manufacturer of the Jadis (I have worked on Jadis amplifiers in the past) to make sure that it won't void your warranty or damage the power transformer. You don't want to have to pay someone to replace it.
Bob Carver told me this when I told him I was afraid I would damage the power transformer using KT 120's in my Citation II:
The KT120s are larger, more powerful tubes and pull down about an extra 40 volts. That allows substantially more power. It is true that the KT120s require more filament power, but not enough to even begin overloading the power transformer, especially since you will not increase the plate current at all. Actually you will bias the '120s at a LOWER current than the '88s, and the output transformer will run COOLER than it is now with '88s. Hope this helps,
Doc, my experience with Jadis biasing is that when they say "rebias", it is always to the same spec (in the case of my JOR 90 - 120 mv, 110 being the ideal value), regardless of the different (or, even same - EL34, 6CA7, KT77, 6550, KT88, KT90) types of tubes used. My other two Jadis amps are cathode bias, and are "plug and play" when it comes to (a pretty wide range of) output tubes.
They are very cautious to ALWAYS tell you to rebias in their products that have such adjustment. I'm not sure of the Defy DA7 values, but I'm working under the presumption that you have them.
Hello music lovers.
In 1990 I bought my first Jadis JA 80 but it was only for el 34 with the old fat philips el 34 in there. (nice). After 2 jears I need new tubes the China el 34 tubes were in one weekend old so I bought tubes from Sylvania 6L6ga jan from 1953(very nice). In 2005 no old stock more. So I bought new Jadis JA 80 with 6550,this was not my sound. (transistor). Next tubes kt 90, I hate them . Next kt88 from Jadis. (nice). Next kt88 from Genalex, yes this is what I want but the kt88 from all concerns are not reliable and live is short about 1500 hour. And there is the new kt 120 I put them in the Jadis and from the first minute yes this is it. I play now five weeks six houres a day with no trouble and the sound on the Wilson Sasha is (live is to short).
I was able to get a schematic from Jadis, eventually, for my Defy 7 Mk 2, SN 623. (They said mine is a Mk 2, but it has the larger power transformer and looks like a Mk 3 to me.) The scan they sent me is a little fuzzy, but it is usable if only for a reference while you verify component values visually in your own amp. I've read that they made frequent changes, so it may not be representative of your exact circuit. I would be glad to scan a copy of it to you if you would like. For my SN they recomend 4 to 5 volts bias current per tube, and very importantly, 160mA slow blow fuses. Also, I know for a fact, your main fuse will not blow in an over current situation if you do not have a proper AC ground.
I would be cautious of running more current through any older Defy 7, especially the Mk 1, which I've read runs hot as is. It has been my experience that the design pushes the limits of its passive parts if the bias is left to stray. Owning one of these things can be a great experience if you properly maintain it, unfortunately I think many audiophiles find themselves in deep water with these amps because they are unprepared and uninformed as to what they are dealing with. With a little research, and some DIY skills, I've found this amp to be my lasting favorite over the years. When is the last time someone personally repaired their old Levinson or Krell that you know of?
Happily, I still have my "upgraded" Defy 7 as my primary amp, but I've gone the opposite direction power wise. I'm enjoying it with the "reissue" Mullard EL34s. With my speakers I have yet to run out of power, or even come close. Jadis makes wonderful transformers, and that is one component I would hesitate to risk damaging. Resistors and caps are easy to replace, but if you burn out a tranny, well, that would really suck.
Good luck, and please let us know how it turns out.
Hello Calle Jr. These are from 2005 with kt 90 from factory, here you can also set in 6550 without problems. After two weeks playing with the original kt 88 from Jadis, bias was too high, they burn out after 30 hours already, the Dutch importer has bias decreases but problem with all brands was 88 kt at 1500 hours is 50% lot and the rest is worn. The 120 kt is deployed without the bias is increased, is possible (this tube is much more power than a kt 90) And this is the most beautiful sound that my wife and I find we have ever received from a tube.
The transformer,s of the ja 80 are themselves less hot with the 120 kt, no matter what and how old the ja 80 is, the transformer is more than heavy enough for the 120 kt.
Thanks a lot Wiebe. I tested the Jadis factory KT88 Gold Lion tubes and have the same experience as you. I have now connected the orange wire on the trafo for 6550-operation and changed for 6550 Winged C. It works good and sounds wonderful, but still, the JA80s eats some tubes. I will test the KT120.