[Freo-1]

I found this post in one of the forums:

VTV 6550/KT88 Shoot Out for Hi-Fi

Genalex KT88 Gold Lion 1969 - 4.87
Tung-Sol 6550 1963 Solid Grey Plate - 4.77
JJ KT88 2002 - 4.63
Ei KT90 1999 - 4.52
EH KT88 Reflektor 2002 - 4.16
Sveltana 6550 2001 - 4.13
Svetlana SVKT88 2002 - 4.09
Svetlana SV6550C Reflektor 2002 - 3.98
Philips Sylvania 1970s - 3.98
Chinese 6550 Valve Art 2002 - 3.89
GE 6550A 1970s - 3.78


The Tung-Sol was voted the best 6550. The Genalex was voted the best KT88 and the best tube in the shoot out. The Ei KT90 was voted the Best Value - it was liked by all reviewers. The JJ KT88 was voted the best new KT88 and also a KT88 best buy.

IMHO, I think this ranking is disingenuous (at best). While the top two rankings are all right, after that, Fugetaboutit!

The GE 6550A and Sylvania 6550 both sound better that the JJ, and are WAY more reliable.  The GE 6550A has roughly the same electrical characteristics as KT 88 (42 watt vs. 35 watt), and long lasting to boot.  For additional info on the GE 6550A, click on the link
http://www.timeelect.com/6550a-ex.htm


 The KT-90 tube in ultra linear has some strange behavior characteristics (but is better in triode).  I think this is because it was modeled after the EL519.

The Genalex Gold Lion Re-Issue was not out when this was published, but most people that use it rank it right up there with the original GEC. Although I personally have had some trouble with them, I'll be the first to admit they sound excellent.

So, I would group them within their wattage limitations. For example, I would be hesitant to use NOS Tung Sol 6550 in a Citation II, due to plate voltages/current issues. 

For the 42 watt, I would put the Genalex NOS KT-88 at the top, with the GE 6550A and Gold Lion Re-Issue just a tad behind. One's overall system would dictate which tube would sound better. The midrange/treble of each of these are slightly different, and what sounds better with system A may not with system B.

The rest of the KT-88's are "horses for courses". I think you have to read the reviews regarding sonic characteristics of each tube, and figure out how to match the tube to your system needs.


For the 35 watt types, the NOS Tung Sol is the reference, with the Sylvania at the next tier. After that, again, it's horses for courses.


So, let the dialog go forth.     

[JoshK]

These rankings without a specific application (ultralinear, pentode, triode, push/pull, single ended, no feedback or feedback, what operating points?) is worse than useless.  One must assume that ordinality will maintain across different operating points and topology but I simply don't subscribe to that non-sense. 

As you astutely point out, the plate dissipation limits of the different tubes puts them in different classes, but also, the optimal points of linearity means they shouldn't be used at the same points just because they can.  Comparing a KT88 at optimal points versus a 6550 at suboptimal optimal points just because it can operate there tells us what exactly? 

The only thing we can garner from this is outliers as they may very well hold their ordinality across topologies & operating points.   Another thing to note is this list is already quite a bit dated. 

I recently read a thread, can't remember where, that brought up the point that we use tube curves and data sheets from 40-50 years ago for new production tubes.  Think the NP tubes have similar curves, or any two tubes of same type but more than a decade apart in manufacturing?  That would be highly optimistic and mostly naive.  In order for a tube to call itself a XXXX type it just has to match some basic parameters, all of which are static, unlike tube curves.   Plate structures, filament structures, etc, etc vary wildly even within a tube type.  Still think they have similar curves?  No wonder they sound and perform different.

[Les Lammers]

VTV's rankings are subjective to say the least. There are too many variable to rank tubes, circuit, cables, speakers, source etc. Personal preference is a large factor too.

[anubisgrau]

I will get very interesting EL34/KT88 SET monoblocks to try them if they can cope with 115db speakers with 15" woofers.

The maker rates JJ very highly but it would be great to know what is considered to be the best sounding tube for SET use from this family.

[Les Lammers]

I have an Audio Note Kit 2 KT88/6550 single ended pentode and the tube *I* like best is the Tung Sol 6550. The JJ El34's are well regarded.

[Freo-1]

Josh makes a number of good points. I do think that the sonic characteristics of a tube/manufacture combination do stay fairly constant over the life of manufacture. The NOS Tung-Sol tubes I have used over the years were remarkably similar sounding from early to later production units. Same goes for the GE and Sylvania 6550 types.

The old tube curves are not as far out as some would have you think. There was some decent test equipment and measurement tools back in the day.

What I think has changed is the "Black Magic" the old tube mavens use to employ to manufacture tubes. The new production tubes should be better compared to the NOS variety. However, especially for the small signal types, we all know that is simply not the case. Just try to find a 6DJ8 currently made that is even close to the NOS Amperex/Phillips/Mullard.  The new production power tubes, for the most part, simply do not seem to sound as good as the NOS, and they do not seem to last as long. I do think it is getting better, but replacing that old acquired experience has proven somewhat vexing.   

[Steve]

I agree with some comments, but doesn't it depend on the design/parts? Most designs use electrolytic capacitors, carbon resistors etc? Sure fire way to skew the results.

I have tried the Jan Phillips and found it to sounded awful. The Amperex bugleboy "D" getters (60 vintage) were good, more pinpointy, but not necessarily better sounding overall. Even changing the frequency response can change the relative ranking of tubes to some degree.

So I would say rankings can easily cause false impressions.

I would like to try NOS mullards sometime and see how they rate.

Now back to the subject at hand.

Cheers.

[MichaelSamra]

 Im new to this particular forum and I hate to be controversial on my first posting but I can't let this go unanswered.
  Many times the rating of a product unfortunately is fed by consumer demand and the high price people are willing to pay.Reviewers many times will evaluate a product as top rated out of fear of looking like a duntz in front of the public.Another words,how dare anyone rank the vintage Genelex as anything but the best..I got news for you.I have all the vintage Genelex and GEC KT88s in my arsenal and many are nos/nib but many are well used but nevertheless very good shape..As far as the sound,they have excellent detail and make great power but they are very lifeless in comparison to the TungSol black plate 6550s or even the TS solid gray plates. So that is first one I disagree with and the only reason I keep the vintage Gens and Gecs are for collectability or when Im displaying my mac amps or my citation 2s for looks.
  The TS black plates on the other hand are my favorite and they defeated the vintage gens and gecs in my mcshane modded macs and citation 2s as well as my upgraded allen organ amps for delicacy and smoothness and an overall romatic ability to pull you into the music and sonic testuria to die for.
    Next would be the Gen 1 and Gen 2 EI kt90s.Yes this tube performs best in triode but it also bested the Genelex in my mac mc60s which run them in correct pentode as well as my Grommes 260 which also run them correctly by raising the plate voltage and lowering the screen grid voltage to just over half and then regulating it.
     Next I would say is the new genelex kt88..I'm not afraid to say that New Sensor did their homework on this little gem..They addressed the shortcommings of the original being sort of lifeless IMHO while maintaining the great attributes of the original..These things become very apparant after 200 hours of break in.
      Next I would put the vintage genelex close behind the new one because the new genelexes do best the original in all but one area and thats top end extension..They are very close tho.
      I also love the Penta Shuguang kt88 solid plate...VERY VERY NICE in all aspects.
      The SEDs would be next and they have a 6550 to die for.
      The EH is pretty much standard equipment in many new amps.
      The worst tube I have found for a kt88 is the JJ..Although it has excellent bass and makes gobs of power,I just can't tollerate the poor midrange clarity..Im a big JJ fan actually and I even talked to Tomas at JJ and he just said we dont make enough money on kt88s to warrant improving them..Oh well!

[bunky]

My 1st tube amp was a Sonic Frontiers SFS 80 And i ran Gen 2 EI KT90's,JJ KT88's and SED winged C 6550's.The EI KT90 was by far my favorite with the winged C 6550 also being a very nice tube,The JJ KT88 in my amp sounded sluggish and unfocused and i had one fail in a spectacular fashion that could be best described as lightning in a bottle.thanks....WCW III

[JakeJ]

My .02 is that most of what comes from VTV is self-serving hype.  Just look at their tube prices.

JakeJ

[JoshK]

Michael,

First welcome to AC!  Those of you who don't know Michael, he is an avid and well respected poster on AA's tube forums (SET, Tube DIY, etc).

I was curious if you have tried tungsol's NP 6550.  I'd like to hear your thoughts if you have.

[JakeJ]

Michael,

First welcome to AC!  Those of you who don't know Michael, he is an avid and well respected poster on AA's tube forums (SET, Tube DIY, etc).

I was curious if you have tried tungsol's NP 6550.  I'd like to hear your thoughts if you have.

+2!  Welcome to AC, Mr. Samra.  Very good information as I would like to get more output tubes for my VAC amps but need more info on new production vs. NOS, western vs. eastern, etc.  This input is greatly appreciated.  Kudos on the fine vintage inventory as well!

JakeJ

[HT cOz]

Michael,

First welcome to AC!  Those of you who don't know Michael, he is an avid and well respected poster on AA's tube forums (SET, Tube DIY, etc).

I was curious if you have tried tungsol's NP 6550.  I'd like to hear your thoughts if you have.

I second that welcome and wonder how the NP Tungsol 6550 stack up?

Thanks,
Robert

[Thebiker]

I have not used the JJ KT88's, nor will I even give them a try in my Cary.  Reason being that a few years ago I purchased an octet of JJ EL84's for a Manley Stingray from a reputable dealer that I have bought other tubes from without problems.  This was supposed to have been a "matched octet" and supposed to have been highly thought of in the audio world, based on reviews I had seen.  Out of 8 tubes, only 6 would bias to 250mV.  The other 2 wouldn't get above 220mV.

Since then I steer clear of all JJ tubes.  May have been a fluke.  But I won't go there again. YMMV

Walt

[bunky]

I follow both Mr Samra and Jim McShane over at AA because they are the tube Guru's on that particular forum.I failed to notice that Mr Samra's post above my previous post in this thread was his first one here at AC  Welcome to the Audiocircles Mr Samra 

[galyons]

Welcome Mike!

Tube comparisons, without practical equipment and circuit information are, IMO, really not very valuable.  It makes a big difference on how a is tube used.  I have Rogue Magnum 150 monoblocks. They use a quad of '88's per side driven by 2 AU7's and 1 AX7.  The Rogue design is conservative and does not drive the tubes hard. The amps have been modified with Russian PIO caps. I listen to blues, dino rock,  female vocals, classical and jazz

I have used the EH, Penta, Winged C Kt88, Winged C 6550A, Ruby Shuguang 98's and GL reissues.

The GL Reissues were the best. The Penta's were nice, but I had reliability issues and my Rogue amps do not run them hard. The Penta's were pricey and 2 of 8 went within 60 days of moderate use. Not, IMO, a good value if this is indicative of the reliability.

The Wing C were too soft and rolled off at the extremes. I am a big SED/Winged C fan. I used the 6L6GC''s in my, now, secondary amps, for many years. I wish that I liked the SED '88's better!  The Winged C 6550A's were solid, reliable, but not as musical as any of the KT88's. They are my default back-up tubes. They are "bullet-proof"!

The Shuguang 98's were very nice. Good bass and treble. Excellent soundstage, but they were bested by the GL reissue.

Then the EH's. The EH's do 95% of what all of the "Top Shelf" others do well for much less money. My only real complaint with them was that the treble is a bit glaring and harsh. But, again, for the money, a great value!

Your circuit will play a role in what works best for you. Take any rave or rant with a "cowlick" size grain of salt. Unfortunately, there is a high percentage of "axe grinders" amongst us.

Cheers,
Geary

[DustyC]

My amps (C-J MV75's) are tough on output tubes. As such I haven't tried all the usual suspects except the 6550 GE and winged "C" Svets. They both have held up, giving good service for the past 4 years. Sonics? I prefer the GE's slightly but the Svets are available in mass quantities and seem to last just as long.
I profess puzzlement as to why the big sonic fuss over output tubes when most of the sonic attributes of an amp lie with the input and driver tubes? (say 15% output, 85% input and driver)

[twitch54]

My amps, just the opposite of Dusty's are easy on their KT-88's. I'm running a pair of Rogue M-150's with the Genalex Gold Lions biased to 40ma. These tubes should last fairly long under these conditions I suspect. I've got approx 400 hrs on them and couldn't be happier.

[mfsoa]

I use the reissue Gold Lion KT88s in my VAC. I don't have anything to compare them to other than the original, old and tired VAC tubes.

But to me they sound great.

I lost one after about a year and just recently replaced it (Thanks again, Mr. McShane).

-Mike

[Freo-1]

Welcome, Michael!  Glad to see you here.

The Penta KT88SC and Gold Lion Re-Issue are both very good sounding tubes.  It's hard to say which one sounds better. I would think either tube would meet one's requirement depending on a given systems balance.

I (along with Michael) would state that the Tung Sol 6550 Black Plates are the best overall sounding of the bunch. (The price is VERY HIGH though).