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After nearly a year of consideration, I gave in to the comments posted here about the Ei KT90 tube. Some were not so positive, but the overwhelming majority of you agree that the KT90 is a serious f'ing tube. So, I ordered up a quad and slapped them into my modified JoLida 502A (not too heavily modified... new input wires, Auricaps, and resistor change to allow biasing for EL34 and 6550).I had read that some people found this combination rather poor in the JoLida equipment. I don't know what pipe these folks have been smoking but I've been listening for several hours now and am absolutely amazed at the difference it has made over the Svetlana 6550's and EL34's I've had in my tube arsenal.
This is, to put it mildly, the best combination I could imagine! The KT90's have totally revised how this amp sounds and I *love* it.
The midrange is vastly improved over the 6550/EL34... it's clean and highly detailed! It's deep and expansive. Soundstage depth increased dramatically. It's analytical enough to satisfy my needs for resolution yet it has never once lost its musical finess.
The bass control and impact is astounding! The KT90 packs some serious oomph, yet it's totally controlled and finely detailed. Bass guitars now have strings that can be heard, xylophones now have mallets, etc.
The upper end is now detailed and airy! It's very clean, smooth, and refined.
Again, the midrange detail is what blew me away the most. I have not heard this much detail in anything less than the most analytically anal solid state amplifiers. Yet at the same time, it has none of the shortcomings of these amps.
I'm very happy with the KT90 and cannot recommend it enough! If you have an amp that takes 6550/KT88's, you owe it to yourself to give the KT90 a try. It knocked my socks off!
Follow Ups:
The KT90 just gets better with use imo. At first I thought they were a bit too "analytical" even though they added better definition and extended range to my current rig (Quicksilver Silver Mono's). I had used primarily Svet KT88 prior (which I perceived as a very musical presentation, but less defined), and mulled at first wether I should return to the Svet's. I stuck it out and let the KT90's mature a bit, and am glad I did.
Amp designed by me with some help and suggestions of the Asylum. About 380V on the plates and screens...bla-bla-bla. I'll let you know when I finally get them built. i suspect I'll have trouble making it sound bad.
The tube met a few design requirements. First is reasonable price/availability. Some NOS is OK if there are few enough folks using them or enough of the tube was made in first place. Things for front ends like 6SN7 and some of its cousins are OK. Second is its huge plate diss. rating. It allows reasonable power whilst remaining in Class A. and not this BS about A for first x watts and AB to full power, though that is another rant in progress.
regards,
Douglas
ps. on top of all that, it is a cool looking tube
"I've been listening for several hours now"DevoX,
I've considered trying the KT90 myself, but I'm confused: Is the above the extent of the burn-in time? If so, perhaps we could prevail upon you for an update in a few weeks? My sets of output tubes have tended to change significantly -- even radically -- on up to 200 hours. (Some sounded so bad, in fact, that I almost trashed a couple of quads in despair before they truly came into their own.) I'd be interested to know what changes you hear, if any, later.
Best of luck, JH
I am letting them burn in for several days here. They've got about 30 hours on them now and the sound is just as good as it was in the first five minutes. They will be burning in all weekend as I re-examine my CD collection. I hope the sound doesn't flake out on me, I am really in love with these power tubes and would hate for it to "soften up".-- Robert
I must admit that my experience with KT90's was quite different, which just goes to prove that different applications produce different results. First, in my AES DJH Superamp, which runs them at 495 VDC in push-pull triode mode, it took about 100 hours of burn-in before they would not blow my tube fuse. I am sure the guy at Radio Shack wondered what I was doing buying all those fuses. So I was probably biased (pun intended) against them from the start. Second, I just couldn't see what all the fuss was about. Yeah, the KT90 was OK, having an extended bass, good dynamic range, good detail and transparency, and clean highs. But in my amp it was seriously lacking in warmth, fullness, soundstage size, immediacy. Compared to the Sylvania 8417, T-S 6550, Tesla and GEC KT88, GEC KT66 and KT77, Amperex and Mullard EL34, heck even the Svetlana EL34 and JJ E34L, I just didn't think the KT90 was that great. I tried all kinds of bias settings, but in my rig at least, the KT90 was a very mediocre tube. Glad to hear it worked well for others.
You're absolutely right. It's an interesting description about the differences in circuits. One person's garbage is another person's gold. I will say that after listening, I can understand how someone could describe the KT90 as lacking "warmth" as opposed to the EL34 and 6550's.I tried some Svetlana EL34's and they really were not to my personal liking. The EL34 sound was very sedate and loose to my ears. The 6550's was a bit more up-front with things and I was relatively happy with the performance I was getting. My inefficient speakers, however, seemed to suck a lot of power off the amp leaving the sound a little too dainty.
I finally figured I would try the KT90, for the hell of it, just to see what happens. I read some comments about the KT90 being a poor choice for my amp, but who am I to believe everything I read on the Internet, right?
With the KT90, I get all of the sound "texture" that I could want with none of the overtly analytical sound of high-buck solid state gear. I am in tube heaven once again!
But yeah, I understand that this sound is neither wrong nor right. It's all a personal choice. I will keep my other power tubes around to roll with now and then. It's still a fun hobby. :)
-- Robert
sounded woody and poor for many hours. I tried this tube over and over. I would leave it in for background music. After about 500 hours it changed. I now have many thousands of hours on the quad, in a Cary amp, and in either triode or pp, they sound fantastic, compared to GE6550, EL34's of Mullard and others, Kt88's of current productions and other tubes. But it took many hours to get there.They are biased around 55mA and a voltage of about 375.
ja in partialy cloudy and breezy, Tucson, AZ
Does anyone know how long these tubes last. I have them in an amp made probably 1992-1993 and have been wondering if they are about to run out anytime soon.
What signs should I be looking out for to suggest that these tubes are due for replacement?
Thanks.
I have just got my first set, so I can't really comment with authority. However, I did read that the KT90 is a real work horse and is tough as nails. It apparently lasts a very, very long time and can take quite a bit of abuse.-- Robert
Hi there,my two cents on the topic:
First, I have to admit that in the PP amps I tried them I was not
entirely pleased with the sound - preference went to EL34 or KT88
- in Ultralinear-Pentode operation - however, in a SE triode-wired
setup the pair I listened to was quite outstanding, beating the living
daylights out of the GE 6550s they replaced.As for the lifetime, the ones in the SE amp - using the permissible
anode dissipation in full, lasted for less than 1000 h before getting
dull - by loss of emission. This happened twice in a row, with matched
pairs from a reputable importer.A shop owner I know uses them as standard in the Jadis gear he sells.
The pre-tested ones from Jadis last 2000-4000h, whilst his trial of
stuff directly imported from the factory did deliver mixed results,
with life between 200h (and subsequent runaway with deformation of
the anode and other electrodes) to 4000 h. Some were gassy and
therefore useless out of the box.It seems that there is (or has been) an issue with the QA of EI.
As for the good examples, they are _very_ sturdy. The intestines are
based on a horizontal line deflection valve for TV sets, the EL519,
which gives the valve catodes with high impulse current resilience...Best regards,
---mb---
======
Try again: EL156 .This was the tube that DM brought to the Ei factory's attention. He wanted an AUDIO tube, a super KT88/6550-type, higher plate dissipation, tolerant of high voltages, octal based, no plate cap, and definitely NOT a horizontal deflection TV tube.
If he wanted TV tubes we could have gotten EL519's cheap all day long and saved oruselves all the hassle.
While it is true that Ei were making EL519, and the innards might appear to look similar, it is very important to make the distinction that the KT90 design was NOT based on this tube.
As for tube life, that will depend on the amplifier design, and plain ol' good luck. I have documented cases of KT90's running +50,000 hours in recording studios in LA, in our amps, never switched off, in a dedicated air-conditioned rack.
Cheers, EveAnna Manley, Manley Labs
Please correct me if I'm wrong. But wasn't the KT90 (or KT99 which I believe are basically selected KT90)based on, or "inspired" by the old Luxman 8045G that was manufactured for them by NEC? They look very similar except that the KT90/99is a little taller. The internal elements look the same too, except for being proportionately larger to fit the taller glass envelope. I also believe Gold Aero was rebranding KT99 & converting them to 8045G by rewiring & new base. I have some of these & they are nearly a direct replacement in the Luxman MB3045 amps (for which the 8045G was designed) requiring only the repositioning of an existing resistor on one of the socket pins.
I beg to differ.The tooling used by EI for anode as well as for the mica discs is the one used for their 1980ies EL519s - the grid configuration is different, but the anode looks like a carbon copy.
I challenge you to do the comparison.
The EL156 is somewhat different - it is based on the LS50-family,
and a real pentode. These two and the EL152 share the basic configuration, but differ in the envelope, connection layout and internal capacitances, as the latter was optimised for VHF use.
The EL153 is similar, too, but a tetrode with beam former...This is easy to see - just take one of each and look at it.
Mr. Manley may have intended to get a EL156, alas, this did not deliver. The KT90 is a reasonably good beam power valve, but it is nowhere near the EL156 in properties.
Compare the curves.
If you are in for a _good_ EL156-clone, they are produced in China now.
If you are in for an interesting beam power valve, take the KT90.
Regards,
---mb---
======
I listened to these with the Jadis Orchestra Reference Int. Amp. It sounded lush with very open holographic mids that can even drive 85 dB spkrs. The KT-90 is the WE 300B of Beam Power Tubes.
EI KT90! What a great sounding output tube other than 300B. Several years ago, my friend modified my Citation II and suggested that putting the KT90 on it and wire in triode mode.Today this set still one of my reference amplifiers! Happy Listening!
... but I am glad you did.As we know, not all tubes work best in all amps, and people hear different things going on but it's nice you found a good synergy in your amp with those tubes.
I remember my first ever visit to a tube factory was in early 1990 seeing the KT90's get born at the Ei factory. Cool stuff. (way cool in January in Yugo-land...)
Have fun!
Cheers, EveAnna Manley, Manley Labs
of this tube. Do you know if this is the case? I have always wondered about this.Thanks,
ja in clear and cool, Tucson, AZ
I was there at the factory twice in in January 1990, mid 1991, and DM went a third time without me.I was first in Nis the first week of January 1990 where they showed us the first prototypes of the KT90. There had been some correspondence between DM and the Ei factory for alomost a year before our visit as to what he wanted them to build. (See my post above regarding the KT90 NOT being based on the EL519.)
The actual engineering of the guts of tube was done primarily by the head Ei engineer, Blagomir Bukumira. We took home four samples and did the initial testing. Some suggestions were made and production began. This was the first "red" paint version. As with any first production run, of which we had to buy ALL of them, there were things to be improved upon.
The second version incorporated some structural modification suggestions from Bill Perkins. This was the "blue" version. You can see the additional spot welds for the concentric inner anode structure if you compare them. More meat. As I have previously posted, in 1993, tubes that fell outside our acceptable parameters were sold to a certain tube vendor who put on a prettier brown base and silk-screened their own "KT99" logo onto the glass.
Then the war started and the embargo went up and none of us could get tubes out of there. The factory also was having trouble getting raw materials IN. Contrary to rumours at the time, the Ei factory was NOT bombed, as we now know.
There later came a third version with wings outside the anode structure but gone was the additional inner plate structure needing all those spot welds.
The latest KT90's I have here, what I would call the 4th version, the sacrificial element tacked onto the anode structure that was square is now circular. Other than that, it looks like the version 3 tubes to my eye.
Here are some quick pictures I just put up for you.
KT90's I have known and loved...
As for bad blood, there was some disappointment as we were supposed to be the world exclusive distributors for the KT90 but this part of the contract was not ultimately honoured by the factory, although it was basically more or less enforced for two years. It was the "less" part of this equation that raised some concern. On the other side, it was understandable that other tube amp manufacturers were not happy to have to buy their tubes from a competitor in the tube amps biz who had been granted "exclusive rights for the whole world concerning advertising, sampling, and sale."I have faxes from Ei-RC from March 1991 outlining all of this. It is quite interesting stuff.
With this, with the war, with all the weirdness that went down, perhaps the factory's memories fall short in some areas, but I was there and I have the original correspondance needed to refresh my memories.
Cheers, EveAnna Manley, Manley Labs
I have always been curious about the response from the factory that I read some years ago about David Manley's involvement. I found it hard to believe that he was not engaged in the development as an interview with him had stated.Thank you again,
ja in Tucson, with the sun going down and a beautiful sunset, AZ
Manley Labs as a company only started in 1993...(You can read about the corporate history here since everyone seems perpetually confused about it.)
Credit where credit is due: it was David Manley who caused that tube to get born and more importantly funded that tube to get born. I was luckily there to witness all that.
It was a big deal at the time as there had not been a new output tube design created in many, many years. And do not forget back then, the Russian factories were still basically hiding behind the iron curtain, the chinese tubes of the time were generally flyweight, and well, it was getting kinda scary. The GE plant had already closed or was just about to (can't remember) and we all were almost faced with a severe tube crisis.
It took real vision, guts, and hundreds of thousands of dollars to make that tube happen, and for that, give credit where credit is due.
Cheers, EveAnna Manley, Manley Labs
they said that Manley had no involvement in the development of the tube. I had also read a number of times that David had helped with the development so I often have wondered why the factory would state this. It seemed like there was bad blood for some reason.Thank you for your response,
ja in partialy coudy, Tucson, AZ
This is one cool lady! I met her at the HT2002 in NYC and got to talk to her about audio. She's got real cool names for the company's audio gears. Many years ago before the invention of digital camera, I send her a 'Telefunken' EL34 for inspection and see if it was the genuine article. Thanks!
that the KT-90 was the standard output tube for all their power amps. That is until the embargo ended their import into this country. The word we got was that VTL (Vacuum Tube Logic) was keeping all remaming stock for themselves, since Mr. Manley was the one who had designed the tube and, as such had some control over who got what.
I do recall a high degree of stress at A.R.C. during this time, as an adequate substitute was sought out. Enter the Sovtek 6550. These tubes proved to be consistantly reliable and, more importantly were available in large quantities.
While no one at A.R.C. ever came right out and admitted (that I was aware of anyway) that the 6550 was not as good sounding as the KT90, you kind of got the feeling from the engineering department that this 6550 was sonically, the second place tube. Whatever the case it was vital, for the continued production of the tubed power amps, to have a steady source of output tubes.
I don't pay any attention to the activities at A.R.C. anymore but I'll bet if these new KT90's are as good as you say, it won't be long before they find their way back into the A.R.C. parts room.
The thing that makes me curious is if they really are out of production. I mean, I see lots of dealers on-line that claim to have this tube in stock. I bought mine from one of them without any problems. I believe Triode Electronics has "current production" Ei ECC83's in stock, and recently put the KT90 back to "in stock" status from what I can tell.Does anybody have the full scoop?
-- Robert
Who said KT-90s were out of production? Ei is still producing tubes, including the KT-90, 12AX7, etc. But for some reason this rumor seems to be out there, even the people at Magic Parts (Ruby) are/were saying the tube is out of production. Strange...There are some quality issues on the KT-90 right now, so the percentage of rejects is quite high; but the tubes are still being made AFAIK. My own stock of KT-90s is quite low, as I've had to reject 80% + of what I received lately. But a good one is a GREAT tube!
The Ei 12AX7 has been changed a number of times, so I believe what Ned's site is trying to tell you is that he has the latest design tube, which is the one in current production.
Also, as far as tube life, I can tell you I've had the original KT-90s in my Citation amp for 12 years - they are still great! I got a couple "red label" sets via David Manley way back in 1991, and then during the first embargo David was able to get Bill Perkins to send me some "blue labels" - just 4 is all I could get. I still have them, new unused sitting in my personal stash except for the set in my Citation.
Oh, I knew they were still producing tubes. But this rumor is out there, along with the one about NATO bombing their factory (ridiculous).As for the "current production" ECC83's, I see that they are now back to the grey plate design. I have last year's models with the chrome plates. Now I also see that they have the Ei "Elites", which I guess have gold plated pins and are specially selected at the factory or some such. I have some Ei 12AT7's that I use, as far as I can tell Ned is the only place to get them.
Have to keep feeding the need to upgrade, I guess! Grey plate, chrome plate, gold pins, rib plates, ticklers, etc. Crazy world.
-- Robert
Hi Robert,You wrote...
"As for the "current production" ECC83's, I see that they are now back to the grey plate design."
Correct you are, sir!
"I have last year's models with the chrome plates."
Yes, they made their appearance last year, and now apparently are history.
"Now I also see that they have the Ei "Elites", which I guess have gold plated pins and are specially selected at the factory or some such."
Actually, the worldwide distributor does the plating and screening. This is good though, as I was rejecting almost 40% of the regular Ei 12AX7s, the "Elite" reject rate is about 10%. Most "Elite" rejects are for microphonics (DESPITE the fact they are screened by the distributor) and for cracking in the glass in the tube base.
"I have some Ei 12AT7's that I use, as far as I can tell Ned is the only place to get them."
That may be, I don't stock them yet as my NOS supply is still okay. But certainly Ned's a good source (and a good guy!).
Hi Robert,You wrote...
"As for the "current production" ECC83's, I see that they are now back to the grey plate design."
Correct you are, sir!
"I have last year's models with the chrome plates."
Yes, they made their appearance last year, and now apparently are history.
"Now I also see that they have the Ei "Elites", which I guess have gold plated pins and are specially selected at the factory or some such."
Actually, the worldwide distributor does the plating and screening. This is good though, as I was rejecting almost 40% of the regular Ei 12AX7s, the "Elite" reject rate is about 10%. Most "Elite" rejects are for microphonics (DESPITE the fact they are screened by the distributor) and for cracking in the glass in the tube base.
"I have some Ei 12AT7's that I use, as far as I can tell Ned is the only place to get them."
That may be, I don't stock them yet as my NOS supply is still okay. But certainly Ned's a good source (and a good guy!).
Yes, the first design KT-90 had a problem running in the Manley circuit, though I don't recall why, nor what David Manley suggested as a fix to the manufacturer. It did work, though.The first design KT-90 works well in the Tube Research amps, without any problem. Great news for TRL owners, because the first design KT-90's sold for bargain basement prices after the redesigned second design.
on the set. One did go weak but I had a matched tube for a back up and the others tested about the same as the new one. I would like to try the version 3 that everyone talks about.ja somewhere in southern AZ.
I haven't used the First design KT-90 for quite some time, opting for KT-88 Gold Lions. What's the word on the 3rd version KT-90?
The third version is what I am raving about. I've heard a lot of stories about the history of this tube but the most common is that it was designed for a speicific few amps.I believe the new 3rd generation KT90 should work fine in an original KT90 amp design. I think the "fixes" really only change the tube slightly so that it will also work in a 6550/KT88 design (since the original KT90 was so close to begin with).
Either way, it's a spectacular tube. I am way impressed and sold "for life"...
-- Robert
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