|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
97.95.45.221
JJ is a company that needs to get it's SH-T together on quality control of it's octal based tubes.I don't know how a company that builds such wonderful sounding tubes as JJ does can have so many failures.That EICO amp I was running E34L tubes in and they sounded wonderful but one of them would separate from the cathode after being on for 20 minutes and lose power.
The funny thing is,the tubes they make for other companies such as Groove tubes don't seem to have quite as many issues..They made the KT88SV for Groove tubes and they also made the E34LS for Groove tubes but it was Groove Tubes tooling and design, and it's a 30 watt tube as opposed to the E34L which is JJ's design that's a 25 watt tube..
I'm starting to wonder if people in Europe have the same reliability issues with JJ octal tubes that we do in the US? They had so dam many tubes come thru with crooked bottles and flashing in the wrong places and microphonic as well.I had the E34L in my stash for 6 years since new and I don't have 50 hours on them and two of the four have issues.The KT77s came thru originally with crooked bottles and under sized pins.
I think their failure rate seems to be in the 50% range within the first two years. Any thoughts?
Honest amplification is better than excessive 2nd order distortion anytime.
Follow Ups:
I bought a Rogue Audio Stereo 100 this past January. I immediately pulled out the JJ tubes and replaced them with Genalex tubes. I didn't want to take a chance with a brand new amp.
Nt
I have never had a problem with Genalex tubes and I like the sound they produce. On the other hand, I have had problems with past JJ tubes I have used.
Well, I've had some funny experiences with JJ, lately. Note that these tubes were stuck into guitar heads, running them into pretty abusive operating points.
I have cooked a few JJ 6CA7's lately thanks to the Marshall Superbass. It runs some 535 plate volts, and not matter what I do THE SCREEN IS A GLOW SHOW! I don't know what the amp's screen draw is, but the amps tired set of Sylvania 6CA7 big boys did not react like that. Frankly, this has been my experience with pretty much any new production tube I have stuck into this amp and others like it. I know these amps eat tubes and are known for instability, but it's pretty ridiculous (and unhealthy for these vintage pieces) if tube sets don't even last 25-50 hours until something begins failing.
On that note, a few days ago in the same SuperBass, I tried a VERY well-matched quad of EH 6CA7's (which by appearance looked better than the JJ design), and they cooked EVEN QUICKER than the JJ. I wasn't even running the amp hard, and I had them biased lower to boot! I cannot find a tube that will allow the amp to sit at a nice bias for its given voltage. I haven't scoped it to really see, but I'm afraid I'll be going into cross-over distortion territory if I bias too cold. Yet, I otherwise may not be able to run the amp at all.
6CA7's aside, a quad of JJ KT77's I had in a HiWatt DR105 died within just a few hours of use. When I had first used them they were perfectly fine! The amp doesn't run over 500V, there was no red-plating, and no screen glow - they seemed perfect for the amp. I jammed with the amp ONCE and set it aside for a few weeks. When I came back to it, it immediately began hissing, spitting and cussing! Checking the tubes, I found the center pair had somehow cooked! So fiercely, the lustrous JJ red had turned into an appropriate CaCa brown.
To be fair, at least they all sounded decent before dying. hahahaha
After all that, the tubes which have shown the most promise is the Gold Lion KT77. I have some loaded into a Marshall JCM800, and they're still barking fine after hours of play time. We have a Marshall Super100 under inspection right now (blew a cap I think). It's getting loaded with KT77's. I'll report back on that later.
All in all, I'm really starting to think it's a thing of overrated specs and poor vacuum... Every amp I have serviced that sits under 500V runs essentially problem-free with new tubes - anything above and the screens simply cannot take the punishment. Passed 500V, things start getting funny with modern-made tube. Looking at most amps on the market today, I can understand why - most have a B+ which never goes beyond 500V, and there's profit in producing and burning tubes like this.
Frankly, screw these oversized tubes like the KT150 and KT120. The GE6550A put each of those to shame, and was 1/2 to 1/3 the size. Gimme a beam tubes and pentodes that do 12-15W of sustained screen dissipation at 600V! I would pay for that!
HEAR THAT, NEW SENSOR! I WOULD PAY! lol
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively and long-lasting. Holy be thy heater.
Ive had some of the same problems you described with their 6L6. It's the one with a single hole on each side of the plate.
The tube suddenly quits drawing current. It can be intermittent. I believe it's the internal welded connections. It could be the cathode, the screen or the plate connections. Any would cause that.
The other problem I've seen with them is the pin size is too small. In Fenders where they hang upside down, they fit the socket loosely and can fall out ot make intermittent connection to the socket.
The only octal JJ's I have are the 6L6GC , with that single hole on the plate. Mine have stood up, but it's the only output tube I have where I hear thermal expansion/contraction on start up and shut down. They have approx one year of use @ 4hr/day. The amp doesn't drive them hard - it was built for 5881's and I give them the same bias.
If JJ made a 5881 I might try it, but the Tung-Sol 5881 reissue did exceptionally well here.
I've been using both power and small signal tubes from JJ for years, in various repairs. All types. I have had almost no premature failures, and no crooked bottles etc.
I can't say the same for the Gold Lion Re-issue KT88 or 300B though.
Dan Santoni
No i do not have problems with JJ tubes.
As reseller i have distributed hundreds of tubes the last year, three
has had problems ( one 6l6 with glowing screen, one 6550 with broken glass and one el84 that was way to high idle current. One powertube has been replaced for my customers, and 2 preamp tubes.
That makes me wonder because I talked to Tomas at JJ a few times and he seems oblivious to the problems with the tubes. CE is the main distributor in the US for JJ tubes and it makes me wonder if they were buying rejects or factory seconds if that's possible? If you would have seen some of the JJ KT77s I got,the bottle was tilting about 10 degrees to one side and others flashed and ran hot.
Honest amplification is better than excessive 2nd order distortion anytime.
My experience with JJ's KT-77s was much like your Mike. I didn't note if they were leaning, so I can't be sure about that. I used the KT-777s in a small =35wpc PP integrated with 2 tubes per channel. After very few hours one arced and took out it's circuit which I had a pro repair. He asked what the F did you do?
OTOH I have had E34Ls blue glass that lasted for years no red plates, arcs, noises etc. etc. They just died with nary a wimper.. I dunno if they have better QC on the purely cosmetic blue tubes as that may be "true true and unrelated."
Steve
I recently tried the JJ 6CA7 and have had no issues. Perhaps the QC has improved?
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: