Regrettably, there are many possible sources. Though the sound is usually indicative of a faulty tube, I've had dirty/poor contacts on tube sockets also produce a similar sound. Rereading your post, did you try swapping the output tubes and then rebiasing? Goodluck.
Jctubes is right, it could be one of a number of things. If it consistently occurs after warmup, it sounds like it could be thermally related. I had a similar problem with my JP80; it was a bad resistor. More likely, it could also be a bad capacitor. After they reach a certain temperature, they start to sputter and sound like they're sizzling when they go bad. These things sometimes are tough to track down, as the effect may only be noticable in a narrow temperature band. I'd suggest you find a good repair facility or contact Jadis if it's still under warranty.
If you have to contact the local Jadis distributor for repair, be forewarned... When I purchased my Defy 7 Mk III used and I called just to get some additional info on the Defy 7, he was trying to convince me that within a few months I would have to spend a few thousand dollars to fix the power transformer (he quoted $2.5K to replace it... yeah right, on an amp at the time that retailed for $4500). Instead of buying the used Mk III that he claimed was a piece of junk, I should buy a Mk IV direct from him instead (for a few $K more nonetheless). When I told him I didn't want to spend the money, he hung up the phone on me. Needless to say, several years later it is still running like a champ. I know the distribution company is the same group but I don't know if the person I spoke with (who was the President of the company at the time) is still the person in charge. Anyone else have a positive experience with the distributor? My suggestion is just make sure you don't get screwed when you get it fixed.
Thanks for all the advice. I did swap power tubes as JCB TUBES RECOMMENDED, THE PROBLEM STILL EXISTS. I also had a negative experience when dealing with Northstar, the importer of Jadis equipment. I will absolutley not send my amp to them. Any suggestions on a knowledgeable technician in the New York area?
Yes. Mike O'Keefe at Audio Outlet has a technician in upper Westchester or Dutchess County that he has referred his customers who own Jadis to, including me. He wasn't able to find the problem with my JP80, but that unit is highly modified and it took Andy Bouwman, the guy who did the mods, over 4 months of constant testing to find the problem, so I cannot fault him at all. If you call Audio Outlet, they may be able to help. I may also have the tech's number at my office, if I'm lucky enough to dig it up, but don't count on it....
I think Rcprince is the person you should listen to for help in the New York area. He is VERY knowledgeable in regard to Jadis. If the problem is a resistor or cap(may also be a faulty connection), you might want to do a parts upgrade while the amp is apart. There is a shop in Philadelphia that used to sell Jadis. He stopped carrying Jadis last year. Seems that the US Jadis dealer network is all but gone. He reports his issue is with the product support for US customers. His stated opinion is that the sound is impeccable, but the support is abysmal(hopefully, I won't have to find out firsthand). I have no experience on their quality of service, but the owner says they are excellent(would he say otherwise...). If all else fails, and you don't mind driving 90 minutes, I could refer you to him.
Got the 7mk4.Had a similar problem. Mine sounded like bacon frying w/o the aroma.Exchanged just the very front tube R/to/L.My center immage shifted.Not sure why that happened.Couldn't live with that. I re swapped back. While the amp was playing,I pushed down on this tube with a wiggly motion/ problem gone.Be nice if yours got cleared up that easy.
Trelja's correct on this--there is one authorized repair facility in the US I know of, and he's located in Colorado, I believe. The importer has narrowed the dealer network considerably. You might also want to ask Lyric Hi-Fi in Manhattan, as I believe they are an authorized Jadis dealer or at least have been while Northstar has been the distributor. They may have a local recommendation as well.
One more possibility is Savant Audio down in Princeton, who I believe has a technician who can service Jadis.
I dont mean to get off the subject, but Jadis has always been on my short list to buy and try. Isnt the beauty of a tube amp design is its easy of repair. Ive been told that there a less than a dozen platforms by which tube amps are based therefore any qualified tech should be able to repair most problems encountered. Most manufacturers do not use custom caps or resisitors which are commonly the problem, therefore getting replacement would be somewhat easy. Am I wrong here? I am fortunate to live near a hobbyist/amp designer who has managed to diagnsose and repair every tube amp problem ive had.
The spitting is caused by the point resistor for the driver
tubes. It is a 100K, 3 Watt resistor. BTW, Jadis transformers are guaranteed for life. If one fails, the owner does not pay for a new one. It is replaced free of
charge. The Mark III never sold for $4500.00. The west
coast Jadis dealer is Brooks Berdan at 626-359-9131. He
is located in Monrovia, CA. Hope this helps. Good luck.
Thanks for all the advice. I appreciate you guys for taking the time to respond. I will post a follow up with my results.