JJ KT88s and other octals

[Jim McShane]

Originally Posted by kevinkr

I guess I am confused because SED (Svetlana Electron Devices) was the name of the joint venture company, but I guess New Sensor did not get the rights to that name, along with Svetlana and the "S" logo? Sorry for inadvertently adding to the confusion, and it is confusing. Noted in checking the new sensor site that it now comes up under "www.svetlana.com" and all of the S branded tubes are not for sale to EU countries.

Unfortunate news about the 6550C, it was a good tube IMLE.

Yes, since they won the rights to "Svetlana" in a US court, it limits what countries in which they can sell tubes they've branded with that name.

You're correct about the rights - the "winged C" and SED logos were not purchased in the bankruptcy.

Don't feel bad if you're confused - you're FAR from the only one. I still deal with it all the time, although less so now than a few years ago!!

[pedroskova]

I've got a pair of Svetlana 6550B's from the mid '90s - the "clear tops" with the disc getters attached to the plate. Googling these brings both praise and scorn. Anybody have experience with these? Should I build around them, or should I build around the current EH 6CA7's that I also have?

[rknize]

I remember the "B" version having issues back in the day. The "C" version was/is much better.

[kstagger]

Just my .02c - I don't like running (most) modern power tubes above 450-475VDC. The metallurgy and cathode material are pretty good but nothing like the olden days - or perhaps I'm just being nostalgic.

I had a pair of SED 6550cs in my old Dynaco Mark IIIs and also used them in my last SE project - which also could handle the Shuguang EL156. I thought the Chinese EL156 sounded better but I had problems with screens shorting - the current meter would peg before the fuse blew. The same pair of monoblocks took a leap forward when my friend bought over a pair of old Tungsol 6550s.

[tubelab.com]

I hope we don't start seeing RCA and GE tubes.

I talked with someone well connected in the guitar amp business about a year and a half ago. He was worried about the current crop of junk tubes and explained what was being done. It now seems that nothing came of it but the plan was to build new production tubes here in the USA (Chatanooga Tennessee) and sell them under the RCA brand. The first tube was to be the 6L6GC. I would welcome RCA's under that plan, but probably couldn't afford them.

[rknize]

Originally Posted by tubelab.com

I would welcome RCA's under that plan, but probably couldn't afford them.

Indeed. Made in the USA would mean prices of the likes of EAT and Western Electric (Richardson).

[richwalters]

Originally Posted by pedroskova

I've got a pair of Svetlana 6550B's from the mid '90s - the "clear tops" with the disc getters attached to the plate. Googling these brings both praise and scorn. Anybody have experience with these? Should I build around them, or should I build around the current EH 6CA7's that I also have?

I find them emission sensitive, i.e slight variations of heater currrent easily messed up the quiescent running figures...although they look rather bland I've found they can handle the C version. IN UL the cue is to avoid running the whole 6550 group above 450V B+, that is all recent types. The only version that can take more stick than a KT88 is the NOS famed GE and JAN versions with a green logo which are understandably pricy and in very short supply.

The only versions I've had serious problems with is the Coke bottle New Edition 6550 from New Sensor which I find has serious longevity problems. A pity because they have a generous glass envelope.

richy

[richwalters]

Originally Posted by kstagger

Just my .02c - I don't like running (most) modern power tubes above 450-475VDC. The metallurgy and cathode material are pretty good but nothing like the olden days - or perhaps I'm just being nostalgic.

Agreed. Although I'm running EH KT90's in my 200W amp at 575V, (using these tubes, this is the lowest B+ voltage in parallel pair p-p that will give this power), it's fitted with IR sensors aimed at the hottest place on the anodes to forewarn of tube runaway. I shall see how long these new ones hold up. My MOV KT88's can take this voltage but it's a waste to put'em in a studio amp that gets thrashed.
The chemistry stuff....that's I recon where all the problems are despite carbon and gold coated electrodes.......poor metal annealing in a reducing atmosphere which is mean't to suck out undesirable gasses. This costs time, money and I suspect not enough time is devoted to this important process.

richy

[sajti]

Originally Posted by rknize

They are available from TubeDepot, TheTubeStore, and Jim McShane as well. As I said, the big Saratov power tubes all seem to have the same or similar plate structure. The Winged-C tubes look quite different.

The real Winged C 6550C/KT88 has square holes on the plate. The "Svetlana" tubes have round holes.
I get my 6550C-s from TAD. Very well matched. Unfortunately it looks that they finished to sell it.

Sajti

[Doz]

Originally Posted by pedroskova

I've got a pair of Svetlana 6550B's from the mid '90s - the "clear tops" with the disc getters attached to the plate. Googling these brings both praise and scorn. Anybody have experience with these? Should I build around them, or should I build around the current EH 6CA7's that I also have?

I have used loads of these... great until about 5 years ago, when something changed ... like the JJ's, bottles weren't square on the bases... don't even think about trying these in an oddwatt... one tube will always run away , no matter how good the matching (so it seems). Many an hour spent scratching my head, checking, measuring , finally solving the problem with a set of KT88s!

Used to love them in Ampeg SVT's... no more will I trust them now... got 4 left and afraid to use them in anything, they'll wait until I design round them ...

Tung sol 6550's seem OK, as to "Winged C" Svetlanas, which I've both had from HotRox in the UK.