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Old 16th December 2003, 07:14 AM   #1
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Default Electro Harmonix KT90?

There are rumors of this tube comming early next year, there are samples already out, anyone got any info on it?
Cheers George
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Old 16th December 2003, 02:00 PM   #2
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KT90 is one tube I've never used. If and when it's reintroduced, I doubt it ould be the same price as 6550 class. What makes you choose this one ?

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Old 16th December 2003, 03:09 PM   #3
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Hi,

Quote:
There are rumors of this tube comming early next year, there are samples already out, anyone got any info on it?
The KT90 has been produced by EI for about 10 years.
The latest version is V 3.0 but I don't know in what it differs from the previous ones.

Much to my surprise I just found out the EI site is down....Does anyone know whether they're still producing?

Maybe EH is sourcing it from of the USSR plants, it's basically a resocketed EL509/6KG6A.

If anyone needs a datasheet, let me know.

Cheers,
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Old 16th December 2003, 07:18 PM   #4
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http://www.audioasylum.com/audio/tub...es/101623.html

If you read what being said about the old EI KT90 , you`ll understand why i`m a bit excited about EH doing one. Read all the posts and how this tube was developed in conjuction with Manley Labs.
And it also explains how the KT90 bears very little resemblence to the EL509.

Cheers George
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Old 16th December 2003, 08:21 PM   #5
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Hi,

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And it also explains how the KT90 bears very little resemblence to the EL509.
Let me assure you that I am 100% certain that it was a resocketed EL509 whhen it was developped and David Manley had something to do with it....He ordered the first batch of 10.000 pieces which is a requirement for start-up production runs at the EI factory.

I like the EL509 and I like the KT90 aswell but urban myths are, well, urban myths.

Cheers,
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Old 16th December 2003, 10:39 PM   #6
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Much to my surprise I just found out the EI site is down....Does anyone know whether they're still producing?

Frank

This spring I purchased 10) KT90 EI tubes along with 10) EL34's and 30) 12AX7's

The site has been down for a long time but the factory is up and running.

Hope this helps.

Joe
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Old 16th December 2003, 10:50 PM   #7
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Hi,

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The site has been down for a long time but the factory is up and running.
Thanks, Joe...

Yes, that's reassuring as they are sole the makers of some less in demand types such as the 12DW7 and 6FQ7 amongst some others.

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Old 17th December 2003, 01:37 AM   #8
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fdegrove, Frank the el509, looks nothing like the KT90, you sure you do`nt mean EL519 as that looks almost identical, as for the similarties, Manly says this about them.


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



Posted by Vanimal Manley (M) on November 08, 2002 at 15:09:43
In Reply to: I once read that Manley Labs helped with the development. . posted by John PA on November 07, 2002 at 21:13:23:


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.


http://www.manleylabs.com/galleria/KT90.html


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

Cheers George
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Old 17th December 2003, 06:11 AM   #9
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Quote:
Originally posted by georgehifi
The second version incorporated some structural modification suggestions from Bill Perkins. This was the "blue" version.
I can confirm that bit -- i've seen the drawings Bill did.

dave
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Old 17th December 2003, 12:52 PM   #10
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Hi,

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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.
Not very likely if you'd ask me. Don't know about yoU guys but buying rejected tubes from someone is one thing but removing the octal base to put on one with a different colour is plain lunacy.

The EL509/519 as they're often referred to in one go by most vendors are cousins, the 519 being the strongest of the pair.
Visually there isn't much difference to go on except when you have real NOS Philips ones.

Does anyone have any idea what it's like to correspond, even talk to anyone working at the Nis factory back in 1990?
I do and it's not easy as most of the workers didn't speak a word of English.

Does anyone have any idea what the tooling cost is like to manufacture a new tube? You don't want to ask, believe me.

Ah, the wings...Guess the factory forgot to remove them from the 509/519s too?

Anyway, bedside stories aside the KT90 is certainly a good powertube.

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CONTROVERSY # 2

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