Sound of SED Winged C KT88 vs. SED Winged C 6550's

Curious as to what if any sonic differences I could expect in comparing the SED KT88's vs. their SED 6550 counterparts. I've researched the forums quite a bit over the last month or so and even asked the question to Kevin Deals gatekeeper @ Upscale Audio... his response was that there was little to no sonic differences between the two.

My amp is a McIntosh MC275 MKV, currently using the stock McIntosh KT88's, which I've been told by Audiogon's Nsgarch, are SED KT88's.
Well Kevin may not have heard a difference, but if he is honest about it then he needs to tune up his ears and/or his equipment. I think he is just 'position' adverse and as a sealesman he doesn't want to jeopardize any potential sales.

In my experience, and just for the fun of it I have to mention that this was formed from using Primaluna amps (as well as four other ones) the SED KT88 is a bit 'full' in the upper bass and the upper-mid range is a bit elevated. Gives them a little of the sense of sparkle. The SED 6550 is much more linear throughout the FR. Tight, non-bloated bass, smooth midrange, and slightly rolled highs.

FWIW, I happen to like the SED KT88's in the PL5, but not anything else I own, when I compine it with the PL3 pre-amp. I prefer the SED 6550 compared to the SED KT88 in my other amps. Actually I've started to grow fond of the re-issue Tung-sols. But they take forever to break-in! :-)_
Newbee - just for clarification, I never got thru to Kevin Deal, as one of his helpers would not let me talk to him... so it was one of Kevin's employees that said there was no sonic differences between the two tubes.

Thanks for the useful info... the sparkle of the SED KT88 is what I'd like to move away from.

Newbee, can you comment on the sonic differences between a SED 6550 and Reissued Tung-Sol 6550? ... which one has less smear when dealing with complex passages and poorly recorded compress music.

Bit out of topic.

I never tried SED valves, but in my PL Plologue Two, KT88 gives more body, like Newbee wrote, and I think this is what you may expect, generally speaking.
Personally, I compared NOS 6550 Tung Sols grey plates with holes, NOS 6550 Tung Sols Black smooth plates, NOS 6550 Sylvania and NOS GEC KT88, which I am using now. NOS 6550 Tung Sols Black smooth plated are great, but not as much as KT88, however may depend in which amp, or simply putted set up, you are using them.
The bad thing, as always with NOS, they are very expensive, but from what I heard/read, TungSols, even they are below their minimum, still sound wonderfull, talking about Black smooth plated from 50's, but they dont have that magic of GEC, I would say KT88 are more involving/musical as well, at least to my ears.
Getting information out of Upscale Audio isn't as easy as it used to be.

There are some major differences between a KT88 and a 6550 and I have always heard a big difference.

I recommend you try Roger Modjeski at Ram Labs for tubes. It's a much better experience.

I switched from EH6550 to GL Reissued KT88 several years ago and the GL is SUPERIOR in every way. Surprisely GL is warmer but also much higher resolution.

My amps require 4MQ so NOS is out of the question. Looking for a tube with the sound of GL Reissued KT88 but higher resolution. Willing to give up a touch of body and bloom ... I DON'T want a SS sound. I'm satisfy with GL but like to experiment ... a bonus with tubes.

I try not dealing with Upscale any longer. ~A years ago I emailed Upscale, Goodwin High End and Audiowave on a EquiTech 2Q. Only Alan @Audiowave replied and ended up purchasing 2 new units from him. Thank GOD for the internet ... have found many great dealers.
Knghifi, I doubt that you will find what you are seeking with the re-issue Tong-sols. Compared to the SED 6550's their bass is bigger, yet tight, mid-range a tad warm, and highs natural. The SED's are more linear and in the wrong amp they can sound clinical (just as the Tong-sols in the wrong amp can sound a bit too warm). I've never heard the GL reissues but from what I've read I would assume they are similar to the SED 6550's with a bit more warmth and extended highs, but that is a WAG.

FWIW, when I'm seeking greater clarity I more often than not go to the small tubes and find success.

Hope that helps a bit.
This is from "the tubestore" Gold Lion KT-88
"In 1957 Marconi-Osram Valve Co. (Genalex) introduced the "King of Power Tubes", the legendary Gold Lion KT88. This tube became the heart and soul of such classics as the Dynaco Mark III, McIntosh MC275, and Marshall Major. Unfortunately, Genalex ceased tube production in the early 1980s and the Genalex Gold Lion KT88 has become very expensive and hard to find."

"After extensive research and engineering, New Sensor Corp. has reissued the famed Genalex Gold Lion KT88. This tube has been recreated down to the finest detail with gold plated grid wire, carbonized screen grids, and a tri-alloy clad plate structure for exceptional performance and sound quality."

I used these in my Quicksilver V-4's and loved them. Worth checking out!!
I think sounds best with KT-88's rather than 6550's and the best new production KT-88 is the Gold Lion re-issue.
Newbee, thanks for the comparison.

It's tough to roll power tubes since the amp requires 4MQs. I'm satisfied with the sound of the amp so probably stick with GL reissued KT88 when it's time for a new set. Already rolled all the small tubes ... was just curious on SED and Tung-Sol 6550.
The Gold Lion KT88 reissue does not sound the same as the original Genalex KT88.

For that matter, none of the reissue tubes sound like the originals.
Any body have suggestions for a VTL S-400 amp? I had Gold Lion Kt88s when first released a few years back and thought they were bright? Could it have been the fact that they were very early production? Any opinions
SED winged C KT88 are more dynamic and have a little more bass than their softer sounding SED 6550. I preferred the KT88 myself and found the SED 6550 a little too laid back in my system. They definitely sound different, although not in a big way.

NOS vs new manufacture tubes sound different mainly because the oxides that we used and method to manufacture were toxic, and thus are manufactured anywhere but the USA.  Also, many old oxide formulas were lost as the companies were sold for scrap.  Last, the quality of mica mined is no longer available so there are trace leakages going on.

New manufacture may not sound like an original of the same type, but then again there can be vast differences even among same NOS brand year of manufacture.