6550 and KT88 differences?

I have a pair of Hurricanes and I use them with a new set of Chinese KT-88 tubes.
I was offered at a great price matched sets of new Ruby,A-R 6550 tubes with the VTL logo printed on (they were made for the VTL amps by the RUBY corporation) on the tube itself is the VTL logo and on the other side the number:
6550
A
USA
Those tubes look far better made than the Chinese KT-88's
Are they made in the USA and would they sound better than the KT-88 ?

The SED 6550 had a very soft and rich midrange, almost mid hall sounding, not clinical sounding though. It made voices just a little too soft to let singers with an etched voice like Diana Krall sound natural in my system.

The SED KT88s much more dynamic and open sounding, yet still possessed a textured midrange. If you have a bright amp that is bothering you, you might like the SED 6550, if you want to open things up and be more front row center sounding, the KT88s will probably prove to be the best choice. The KT88 for me was the much better of the two choices in tubeds.

I have ASL Hurricans which use KT 88's. Has anyone (or can this be) changes tubes to 6550's...and what was the differnence with the Hurricanes (sound).
Any good prices on KT88?

and now for something completely different...

Try some KT66 toobs!
According to Primaluna these will also work in your integrated 8^)
The 6550's were softer in the top, and in the long run had a somewhat bloated bottom for my tastes.
The 66s on the other hand really spiced things up, it made the music more lively, a bit more forward, yet they offered the speed, detail, resolution, and transparency I wanted without sacrificing the sweetness and body I had grown to love.
additionally I have also rolled the small tubes in conjunction with them making an even bigger impact - the clear top 12au7 very smooth which compliments the 66s well. Along with some Brimar 12BH7s that added to the transparency sound scape .
thanks to the Kats @ the tubemonger for helping me match all the above.
cheers

The 6550's were softer in the top, and in the long run had a somewhat bloated bottom for my tastes.
The 66s on the other hand really spiced things up, it made the music more lively, a bit more forward, yet they offered the speed, detail, resolution, and transparency I wanted without sacrificing the sweetness and body I had grown to love.
additionally I have also rolled the small tubes in conjunction with them making an even bigger impact - the clear top 12au7 very smooth which compliments the 66s well. Along with some Brimar 12BH7s that added to the transparency sound scape.
thanks to the Kats @ the tubemonger for helping me match all the above.
cheers

With respect to its design, the KT-88 is the British variant of the 6550.

In use, they have proven less reliable than the 6550, particularly back in the 80's when their were some especially poor quality Chinese KT-88's that were more roman candle than output tube. VAC sells very good KT-88's.

It depends upon the use to which the tube is put and the production run, but in my experience, KT-88's tend to be a bit richer sounding than 6550's, while 6550's may be more accurate and linear.

If I were to investigate new KT88's I'd be interested in the new Gold Lion reissues. Minimal input yet, but from what there has been they 'sound' like they might be excellent. Don't read too much negative into my assessment of the SED KT88. Of all the tubes I tried in my Prologue 5 (including EL34's and 6L6's)and other brands of 6550's and KT88's it was my favorite. All tubes are agruably colored, depending on your speakers and amp, not to mention sonic preferences. Also, don't overlook the impact you can benefit from in further refinement by changing the small tubes.

Any suggestions on a KT88 brand that's still smooth and extended yet maybe a tad less colored than the SED? Seems like I've heard mixed things about the EHs.

In my Prologue 5 (W/Prologue 3) the SED KT88's have an emphasis in upper bass and a more forward midrange, smooth and extended highs. The SED 6550's had a more linear response with a slightly soft high end and a tight but not bloated bottome end. Tonally the 6550's sound more coolish in the mid range. I preferred the KT88's. The SED has a lot of color that can be attractive, but......

In a Cayin A100T (and 2 other tube amps I have) the two types have a similar sonic signature, but I much prefer the 6550. In it the KT88's bass was a bit much.

I'm guessing that the Dialogue might sound best with the KT88's, but much will depend on the brand of KT88 - they can sound quite different.

Did one have a clearer midrange?

In a Cayin 70T, the general differences between the two boiled down to dynamics. The (EH) KT88s were fast and detailed and so they had great dynamics. The (SED) 6550s had a meatier tone, softer top end, and focused more on microdynamics than anything else. They were quite different but both good.

Arthur