KT88/6550 trials

Thought I would finally post my experiences with various manufactures KT-88/6550 tubes, mainly out of surprise at what was one of my favorites. The KT88 arent cheap tubes to buy, perhaps this may help someone out a little bit.

First choice, and an obvious one by most all accounts, was vintage TungSol 6550. A sparking top end unparalled with any other tubes I have listened too. And mine werent even the famous black plates! Mine have since bit the dust, so off to the new manufactured tubes. Plan on a second mortgage on the house for a set of NIB Tungsol 6550, if you can even find a matched quad!

My next favorite was the reissue Gold Lion KT-88. The best top end, with all other aspects well balanced and very pleasant to listen too. I like these tubes alot, and will spend no time mourning the loss of the NOS tubes and their out of control prices anymore! I hope these hold up well, I have a few hundred hours on them so far.

Next, and here is the surprise, was the lowly Sovetek 6550WE. I got a lightly used quad of these for $40 and figures I would use them as a bench/test set of tubes. But, they sounded good! A top end rivaling the Gold Lion reissues, not quite as detailed in the top and mids but very close. For the price (I have seen new quads as low as $84) these are an absolute steal.

Fourth favorite would be the old GE6550 straight bottle tubes. The best low end, and not too shabby mids/highs. Expensive and rare now, so not really a consideration any more.

Fifth is the Winged C 6550 tubes. Sound very mellow and balanced top to bottom, but maybe a little too much so in that there just doesnt seem to be the dynamics of some of the other tubes. Not at all bad tubes, but I would choose others, expecially since the Gold Lion reissue is not much different in price.

In the rear,and the last one that I have tried, is the Chinese Shanguang GEKT88 solid plate. The Penta solid plate is the more common model sold of this tube. I had high hopes based on some of the excellent reviews of this tube, but I was not overly impressed. Sounded similar to the Winged C, but maybe even a little less top end. I will also note this is the only quad in which I experienced a problem, with one tube failing after about 200 hours. These are expensive tubes, at nearly the price of the Gold Lions. Will be my one and only set purchased of them!

None of these tubes were that "bad", and if my least favorite of the group suddenly became the only version available, I could live with them. I am impressed with what is available at the current time, with new manufacture KT88/6550.

I dont know what I will try next, but am leaning towards the Electro Harmonix KT-88. As you can probably tell from my reviews, my taste runs towards tubes with an extended top end. I have heard the EH KT88 tends towards that characteristic.

looking in my crystal ball, I see you next testing the new tung-sol kt120's. do a search here, and you will find some info, and they should start being available in a couple of weeks.

the jj kt88's get a pretty good rap out there, and surprisingly, I am running 5 quads of valve art kt88's and really do not have much bad to say about them. swapping the gain stage in my amps seem to make more difference (getting into mid 40's 6sn7gt's)

I would say give the EH KT88's a try as well as the EH 6550's.

So far, I have tried the Sovtek KT88 and the EH 6550's in my ST120.(60 wpc)

The Sovtek's sounded good but for whatever reason, I think this amp just pushed them too hard. I went through a few that would slightly red plate if I ran them at the recommended bias.
Like I said, they sounded good with a nice low end and fluid mids. They held bias fine but I had to run them much lower than I liked.( recommended bias is .550VDC, I had to keep them at .510 or lower.)


I have since gone to the EH 6550's and, IMO they are excellent. The bass is very deep and tight. The mid range is nice and natural with the upper end very detailed and open.
They do just fine biased as high as .625VDC but I run them at .550VDC.

Ive seen the Sovtek's used in other amps and they did just fine but I think they just dont like my amp.

Do you think there is any real difference between the EH 6550 and the EH KT88? They look dead identical sitting side-by side.

-Vic

Thanks for the review. It's hard to find this kind of information.

only Svetlana 6550, they are simply THE BEST from sonic point of view

thevic24 said:

The Sovtek's sounded good but for whatever reason, I think this amp just pushed them too hard. I went through a few that would slightly red plate if I ran them at the recommended bias.
Like I said, they sounded good with a nice low end and fluid mids. They held bias fine but I had to run them much lower than I liked.( recommended bias is .550VDC, I had to keep them at .510 or lower.)

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I've had the same experience with the Sovtek 6550. I don't think it's just your amp. If I treat them like a 6L6, they seem to be okay. If I run them harder than about 25 watts overall dissipation, they start to show a hint of red in one corner of the plate. It always starts in the same spot, right next to the seam. It's only on one side of the seam, and on one side of the plate. I suspect there is something peculiar about the internal construction that makes them behave this way.

Otherwise, the Sovtek 6550 is a nice enough tube.

Baele said:

only Svetlana 6550, they are simply THE BEST from sonic point of view

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If you mean the old svetlana from the petersburg factory, ( Now known as SED) I would agree. If you mean the current "svetlana" from the reflector factory, I would whole heartedly disagree.

Russellc

Russellc said:

If you mean the old svetlana from the petersburg factory, ( Now known as SED) I would agree. If you mean the current "svetlana" from the reflector factory, I would whole heartedly disagree.

Russellc

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Of COURSE :thmbsp:

Ty_Bower said:

I've had the same experience with the Sovtek 6550. I don't think it's just your amp. If I treat them like a 6L6, they seem to be okay. If I run them harder than about 25 watts overall dissipation, they start to show a hint of red in one corner of the plate. It always starts in the same spot, right next to the seam. It's only on one side of the seam, and on one side of the plate. I suspect there is something peculiar about the internal construction that makes them behave this way.

Otherwise, the Sovtek 6550 is a nice enough tube.

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This is exactly the issue that I have had with the Sovtek KT88's. Other than that, they sound great and hold bias fine.
Here is a pic of one glowing. Its just doing it in this spot only and not on the other side.



-Vic

I was also surprised at how good the Sovteks are. Yes, the new issue Lions beat them, but not by much.

My only issue with the KT88s coming from the Reflektor factory(EH, Sovtek, what's currently labeled Svetlana, Tung-Sol reissues, etc), is their inordinate short life-span compared to what I'd expect out of a good KT88. I've got a "tube hall of shame" box here, and it's about to over-flow with mostly EH (but a few of the others listed) KT88s, that all failed within 2 years or less of normal use.

OTOH, Winged C KT88s seem to last a long time. As to, surprisingly enough, the most current batches of Shuguang-built Chinese tubes, IME.

One tube I would HIGHLY recommend, for sound and longevity, is the EH KT90. I haven't seen one of those fail yet. Rogue Audio uses them in spades, and we've run quite a few of them through the shop. Nice to have a tube that when you bias it, it STAYS THERE, no matter what. Can't say that about most KT88s these days. Also doesn't hurt that it's put the smack-down on ANYTHING else we've compared it to WRT KT88s, in various amps, for sound! Better soundstaging, in most cases...

I have a theory on why the Reflektor KT88s are unreliable these days... I think they're running their tooling past its useful life, and things are going out of spec. The KT90s are from the same factory- BUT- since that tooling hasn't been around nearly as long, it's not nearly as worn out yet... so, they're much closer to spec and more consistent...

Regards,
Gordon.

Has anyone here listened to the both Sovtek 6550 and Sovtek KT88?

I enjoy listening to the Sovtek 6550 enough that I am more than curious to their KT88. Im guessing the EH KT-88 would be very similar if not identical coming from the same manufacture and/or tooling (New Sensor). My next quad is going to be either EH KT-88 or Sovtek KT-88.

bronco said:

Has anyone here listened to the both Sovtek 6550 and Sovtek KT88?

I enjoy listening to the Sovtek 6550 enough that I am more than curious to their KT88. Im guessing the EH KT-88 would be very similar if not identical coming from the same manufacture and/or tooling (New Sensor). My next quad is going to be either EH KT-88 or Sovtek KT-88.

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I have a quad of the Sovtek KT88's and I like the way they sound. They have a great bass that may be a tad heavy.( I like that) But my amp seemed to run them too hard.

I had a few sets and had at least one in each quad that would have a slight red glow on one side of a plate. No matter where it was in the amp. I had to run the bias very low to not have the red plate and it affected the sound to much for me.

I will be buying a quad of the EH KT88's this weekend from Jim McShane but for now I have the EH6550 in the amp. They both look the same(build wise) but I was told they are made out of different material.

The Sovtek KT88 looks different and has a different bottle shape.
I like the way the Sovtek's sound but, IMO, the EH6550 dose everything better and no red plating issues.

I like both but I vote for the EH6550/KT88.

-Vic

Baele said:

Of COURSE :thmbsp:

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Agreed. I find the 6550 of theirs to be extraordinarily rugged, ditto for their KT88. Not the cheapest, but far from the most expensive. While we're at it, I have found the Tungsol remakes to be excellent as well, typically a little more expensive than the SED 6550. And they look really cool!:yes:
Oddley, I believe the Tungsol is made at the Reflector factory...but they have held up long term, and still are in my P-P amp at this time.
Russellc

GordonW said:

My only issue with the KT88s coming from the Reflektor factory(EH, Sovtek, what's currently labeled Svetlana, Tung-Sol reissues, etc), is their inordinate short life-span compared to what I'd expect out of a good KT88. I've got a "tube hall of shame" box here, and it's about to over-flow with mostly EH (but a few of the others listed) KT88s, that all failed within 2 years or less of normal use.

OTOH, Winged C KT88s seem to last a long time. As to, surprisingly enough, the most current batches of Shuguang-built Chinese tubes, IME.

One tube I would HIGHLY recommend, for sound and longevity, is the EH KT90. I haven't seen one of those fail yet. Rogue Audio uses them in spades, and we've run quite a few of them through the shop. Nice to have a tube that when you bias it, it STAYS THERE, no matter what. Can't say that about most KT88s these days. Also doesn't hurt that it's put the smack-down on ANYTHING else we've compared it to WRT KT88s, in various amps, for sound! Better soundstaging, in most cases...

I have a theory on why the Reflektor KT88s are unreliable these days... I think they're running their tooling past its useful life, and things are going out of spec. The KT90s are from the same factory- BUT- since that tooling hasn't been around nearly as long, it's not nearly as worn out yet... so, they're much closer to spec and more consistent...

Regards,
Gordon.

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I have had very good reliability with the quad of Tungsol 6550 reissues I purchased. I normally am very suspect of the Reflektor factory offerings, maybe things are changing.

Russellc said:

If you mean the old svetlana from the petersburg factory, ( Now known as SED) I would agree. If you mean the current "svetlana" from the reflector factory, I would whole heartedly disagree.

Russellc

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Svetlana in St. Petersburg is still making tubes. The problem is that they will not sell directly to the USA or Canada due to the fact that some company has the rights to their name and trademark. They started using the Russian winged C as their trademark, but for whatever reason, they just don't due business here anymore. even their website says everyone is welcome but USA and Canada. Still, I believe there is a guy in the Ukraine (Odessa I believe) who sells boxes of 100 on ebay every now and then.
I have been using St Petersburg Svetlana 12AX7, 6L6, 6550 and EL34 tubes for years and still do. They are, in my opinion, THE best modern production tubes. Since Svetlana will sell to all other countries, I would be willing to bet you could contact someone who is into tubes and outside north America and they could pick some up for you and then you could work a deal with them to get them here.

Make "tube wingedc" search over eBay, there are enough sellers in USA. Even if they do not list KT88, they may have them, or you can use 6550 instead.

seta1 said:

Svetlana in St. Petersburg is still making tubes. The problem is that they will not sell directly to the USA or Canada due to the fact that some company has the rights to their name and trademark. They started using the Russian winged C as their trademark, but for whatever reason, they just don't due business here anymore. even their website says everyone is welcome but USA and Canada. Still, I believe there is a guy in the Ukraine (Odessa I believe) who sells boxes of 100 on ebay every now and then.
I have been using St Petersburg Svetlana 12AX7, 6L6, 6550 and EL34 tubes for years and still do. They are, in my opinion, THE best modern production tubes. Since Svetlana will sell to all other countries, I would be willing to bet you could contact someone who is into tubes and outside north America and they could pick some up for you and then you could work a deal with them to get them here.

Click to expand...

Actually a lot of places sell them.
Check out the Tube Depot:

http://tubedepot.com/sed.html

GordonW said:

My only issue with the KT88s coming from the Reflektor factory(EH, Sovtek, what's currently labeled Svetlana, Tung-Sol reissues, etc), is their inordinate short life-span compared to what I'd expect out of a good KT88. I've got a "tube hall of shame" box here, and it's about to over-flow with mostly EH (but a few of the others listed) KT88s, that all failed within 2 years or less of normal use.

OTOH, Winged C KT88s seem to last a long time. As to, surprisingly enough, the most current batches of Shuguang-built Chinese tubes, IME.

One tube I would HIGHLY recommend, for sound and longevity, is the EH KT90. I haven't seen one of those fail yet. Rogue Audio uses them in spades, and we've run quite a few of them through the shop. Nice to have a tube that when you bias it, it STAYS THERE, no matter what. Can't say that about most KT88s these days. Also doesn't hurt that it's put the smack-down on ANYTHING else we've compared it to WRT KT88s, in various amps, for sound! Better soundstaging, in most cases...

I have a theory on why the Reflektor KT88s are unreliable these days... I think they're running their tooling past its useful life, and things are going out of spec. The KT90s are from the same factory- BUT- since that tooling hasn't been around nearly as long, it's not nearly as worn out yet... so, they're much closer to spec and more consistent...

Regards,
Gordon.

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Plus one on the KT90s thing, especially if you can find the older ones.:yes:

jaymanaa said:

Plus one on the KT90s thing...

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I tried some KT90, but they didn't sound quite "full" enough at the usual bias levels. I think you probably need to turn the idle current up a bit to fatten them out. Considering the cost of these things, I'd probably stick with KT88 unless you know for certain your amp "likes" KT90.