No love for the KT 90?

Did a search on the forum and found ONE post on the KT90 ... that left me wondering about the tubes and whether they'd work in these amps.

My understanding is they have more of an EL34 "mellow" sound to them than most KT88's. Also that the EH brand tubes hold up to some serious torture tests and are pretty much bulletproof.

Grey on how they sound - web reviews tend to make them slightly brighter at the top than the average new production KT88, with the extra boost on the bottom similar to a KT120. Break in time is longer than usual, but you should hear pretty much as good as it gets before 50 hours.

I expect I'd be able to run them at the same bias levels as the KT120's (60mV) and that they'd be plug 'n play with a bias adjustment to hit those levels. I also figure I'd see approximately the same 5 watt boost over a KT88 in the ST120 ...

*I'm too cheap to pay out the big bucks for the EI version. Get what ya pay for though ...

Seems you got it.....haveing had the EIs i never felt the need to try the EH....i have had EH EL34s
An 6550s....There better than any JJ....Ok sound but theres others same $$...
One thing .....the top on EI... is richer than any EL34...Never got brite as some KT88s...in my setups...i use ESL....thay dont let much pass....you hear all good an Diff....i have for 40 years....i have other speakers...but the ESL are the test.....

Finely crafted by the GuiGuang Factory in China......Golden Gate KT88....some one told me thay great tone......Vary fair $$..................thay were on sale for $19.ea...

https://www.tubesandmore.com/products/T-KT88-GG

In 1956,....I heard my frist tube....i was 5.....Have fun with tubes....justsaying iam Still going.......hehe
In the 80s 90s...i sold Bob Carver .... Bob spoke of Mr McShane...
Bobs a big H/K tube amp lover....



Thanks for the site Bob........

I'd forgotten about the Golden Gate KT88 Super Tube.



Posted up about those a couple years back over on AK and only thing I got back was
.
.
.

(yup ... pretty much nothing)

They've been around for a while, and GuiGuang gets real decent reviews for sound quality and durability. And, like ... they're super! You'd think there'd be more folk using them at $100 a quad?

Have to keep them in mind as another option.

Wow what a coincidence! I was curious about the KT90EH tubes and just bought a set last night. I'm currently using JJ KT-77. I should have them by Friday. The Golden Gate KT-88 are also peaking my interest. They are on Amazon for $100 quad. That might be my next try for power tubes. Can't beat that price.

Personally I am using Gold Lion KT-66 (in a Dynaco/Panor Stereo-80), KT-120 Tung-Sol in my ST-120, TAD (Tube Amp Doctor) 6550's as an alternative (with 12BH7) in my ST-120 and Electro-Harmonix EL-34 in my Dynaco MkIV's. All of them produce some really nice music.
There are differences between them, It is like with food.... sometimes I like a bit more salt and pepper.... doesn't have to be the same everytime :-)))

Here is a link to what is probably the best KT-88 of all times, the EAT (EuroAudioTeam) Diamond. The lady in charge of these tubes
is mrs Lichtenegger (of Pro-Ject fame). These KT-88 are handmade like in the old days and very expensive (350€ per tube.... at a rate of 1.3, that is about 455$ each.) They get the highest praise in several reviews.
For the record, I do not own these because of the expense; It is however "nice to know"

On their website there are several downloads that are interesting!


http://www.europeanaudioteam.com/en/eat-kt88-diamond-valve-000011.html

Tevian wrote:Wow what a coincidence! I was curious about the KT90EH tubes and just bought a set last night. I'm currently using JJ KT-77.  I should have them by Friday. The Golden Gate KT-88 are also peaking my interest. They are on Amazon for $100 quad. That might be my next try for power tubes. Can't beat that price.

Looking forward to your review of the KT90EH. What amp you using?

If I wanted to spend the big bux on designer tubes, and seeing as "different" appeals to me, the hand built EAT's really sound interesting, but then there's the Northern Electric graphite tubes ... real deal at only $180 each ...

Still leaning towards the EH KT90's though ... no big rush ... there's plenty of life left in the KT120's.

pOp  

What was that??

Hello Skizo. I'm using a newly rebuilt ST-70. I posted about it here on the forum. my-very-first-tube-amp

I have recently upgraded the power tran and can't wait for the new tubes. I will try to review as best I can although I'm still very green on how tubes amps sound. Its been interesting so far.

I'm sure I will need a few days to break in the tubes. I'll post asap after I get a feel for them.

sKiZo wrote:(PS ... The Tube Store just raised the price on the KT120 $5 each ... still IMHO a good deal at $216 for a matched quad.)

That is a pretty good deal - that's only about $27.00 more than I get for a quad of them - and Bob is kind enough to recommend me to supply them to people who want them for his amps since I test and match them under real world conditions.

I'm sorry, I just couldn't let that post go by without a response.

Skiz,

The last ST70 I built, and as usual for me in a wood case, I misjudged the distance between the octal sockets, and drilled them so that once everything was done and it was time to install the tubes the KT88s had about 1/16th of an inch space between the front and back tubes.  This was too close for heat considerations, and that's what I get for thinking I'm so good I can just whip out an amp.....
Anyway my solution was to go with a set of EH KT90s as they have a smaller diameter glass envelope than the standard KT88s.  It did solve the initial issue as there was now enough space between the tubes for them to breath.   I wasn't expecting much sound wise but there wasn't much else I could do at this point. I had read some decent reviews of the EH 6550 though, which as far as I can tell is the same tube internally as the EH KT88, but less expensive, so that leant itself to try the KT90s.
I should disclose this amp had the very first Octal driver board I had tried with upgraded 450 volt larger value electrolytics installed. I also took the plate voltages up a tad by using a custom toroidal MKIII power tranny with its higher voltages.  OPTs from Kevin.  Mundorff Silver Oils as the coupling caps.
Once broken in I was stunned by how good this amp sounds, and I have built a $hit load of amps, to include some very expensive OTLs.   This amp with the EH KT90s is by far the best sounding Dynaco ST70 I have ever put together, and by that I mean jaw dropping stupid good.  Again not what I was expecting from EHs.  Certainly not a tube you'd kick out of bed for eating crackers.  That's my experience, I would not venture to guess what someone else's maybe.

I should also have stated I run these KT90s at around .525 to .550 volts for biasing, which for me is a little hotter than the .500 I normally run KT88s at.  This tube has no problem taking it.

Something to keep in mind is that if you bias them at half of max dissipation they should last for a very long time.  Like 10,000 hours give or take.

Jim McShane wrote:

sKiZo wrote:(PS ... The Tube Store just raised the price on the KT120 $5 each ... still IMHO a good deal at $216 for a matched quad.)

That is a pretty good deal - that's only about $27.00 more than I get for a quad of them - and Bob is kind enough to recommend me to supply them to people who want them for his amps since I test and match them under real world conditions.

I'm sorry, I just couldn't let that post go by without a response.

Jim, don't blame ya.

I'm not on his payroll, but Jim McShane is my go-to guy for new-issue power tubes, and although he likes the KT-88s better, I'm very satisfied with Russian Tung-Sol KT-120s in my M-125s. They're robust and can put Norah Jones right in your lap. Also, Jim will get back to you within the day to answer, patiently, even the dumbest of questions.

For NOS preamp and driver tubes, if McShane doesn't have what you want, I would highly recommend Andy Bowman at Vintage Tube Services. There's also a guy near Toronto who deals on Canuck Audio Mart (djrosa@bell.net) in antique tubes; quality stock and honest, and another guy in Seattle with 9-pin tubes I like but haven't the time to look him up.

I would avoid Tube Depot. They list stuff they haven't got, then try to sell you up to the cryo nonsense.

deepee99 wrote: I'm very satisfied with Russian Tung-Sol KT-120s in my M-125s. They're robust and can put Norah Jones right in your lap.

I could get to like that!

GP49 wrote:

deepee99 wrote: I'm very satisfied with Russian Tung-Sol KT-120s in my M-125s. They're robust and can put Norah Jones right in your lap.

I could get to like that!  

I have. She's a beaut. Oooops, thread drift here. Seriously, Norah Jones on vinyl will tell you whether you're listening to sand or listening to music.

Norah's Come Away With Me is one of my favorite torture tests when "tuning" the room. The vocals and piano will point out any shrill or inconsistencies.

(And, what goes around comes around ... speaking of tubes ...)

Yet another option is the Penta Labs KT88SC.



Those are the solid plate "strict copies" of the original Golden Lions and seem to be highly regarded for sound and durability. Repeated theme is that they're rock steady right out of the box. Made by Shuguang and the exact equivalent of their GEC series - just relabeled for Penta. Rumor is they sound better than the black bottles ...

Bit more bux than either the KT120's or KT90's, but definitely different. Yes, definitely ...

EDIT >> Apparently, these are the same thing, only different, for $15 less per tube.



For that kinda difference in pricing, makes me wonder if they're factory seconds. The Chinese are well known for providing product to spec (and Penta apparently specs them high) but they're also known for dealing the tubes that don't make the cut.)

Hmmmmmmmmm ...

Ok returning back to the KT90EH...

I recieved them a few days ago. So far they have maybe 15 hours on them.

I would like to restate that i'm very new to the tube sound. So I hope this opinion will be useful to someone.

Current system is a rebuilt ST-70 using the VTA driver with 6SN7 tubes. Also i've opted for a new power tranny. Picture is the third down on http://www.tubes4hifi.com/ST70.htm main page thx Roy. I'm running all custom speakers and custom crossovers. Dayton Audio RS125-4 x 2 and Tang Band 28-847SD per cab. Listening source varies. Pro-ject turntable and digital sources.

Currently I have them biased to 50ma. I believe my bottle neck for power is the stock ST-70 OPT's. That being said the system provides plenty of power for my needs.

If you haven't seen a comparison check out the pic below. Although the tube glass is roughly the same size the tube elements are much larger. You can see the base is very low profile. I kinda wish it was a little more substantial. At first glance they are not as different looking to the old KT77's as a KT88 or fat glass tube would be. So.. they are larger but not as impressive looking than a KT88 would be I guess.  

At first power up I noticed the highs being a bit soft and the bass was over emphasized. I came across a post with a similar experience so I don't feel alone in this. They have leveled out but there are still very new. Right now they don't sound terrible. The bass is still a bit heavy but not all together unpleasant. Once I get more time on them I will try to give a more detailed impression. Right now i'm on the fence.    Just got the Gardians Of The Galaxy LP. Its not sounding to bad right now.  

These observations are in relation to the EL34 and KT77 tubes I was running previous. Also my complete lack of exposure to any other tube amplifiers. I preferred the sound of the KT77  over the 34's so the 34's were shelved quickly after I got them. I will have to try the 34's again to see if my opinion stands.




---KT77---

Thanks for the info an pic..................I to like the tone of 6SN7 inputs
i have had the EI KT90 for years....these EI are not made any more..the KT90 can take 7-800B+v on there plates....if there ran with 600v on the plates thay do open up an topend gets better....but i dont like the sound of any output tube ran with more 460-80....ran on there plates
But sound wize your right on....the top is not rolled off ......But it sounds to me like the mid is push out an the base sounds fat..some amp input tubes can match well....but the 6SN7 can sound dark with some tubes....KT90,KT88.....an maybe the KT120s-150s.........6550s an the 6SN7 is a sweet setup...an some of the topend i ever had.............
The top-end on the KT77,EL34 well be much more open...well to me
I have got great sound out of my Dynaco MK3 with the old stock 6AN8 inputs....
there top-end can sound brite...the KT90s sound right in this setup.....



Thanks for the site Bob........................

Good info ... nice to see a "real world" review. Also impressed with the EXACT matching based on the box stickers ...

Pushing the bass can be a good thing, and something I like about the KT120's. Long as the mid bass doesn't get muddy, I'm cool wit dat.

Pushing the mids is also a good thing IMHO, as that's where the ears typically begin to fail as we age, or at least fail in the spectrum that's most noticeable, as in vocals. I agree the B+ could be a factor as the tubes will never develop their full potential in the ST120. Then again, same could be said about the KT120's, although they perform extremely well in this application.

Fun research!

PS ... things that make you go "huh"? What's with all the blank posts? Some heavy handed modding going on in the background?

12AU7-12BH7.............Bouth being vary close to the Big boy the 6SN7...may give better top on the KT90-120...well i think thats your point about the 120s in your amps...sounding good to you..
I have B&Ws..Apogee speakers....that can get a hot on the topend...6SN7 an the KT88-90s can sound great.....
But get a littel dark on the ESLs.....Magnepans...this is where the 6550s come in...thay need the 6SN7 to give that richness but still...open up the top up....hehe...tubes in 2014 gofig



Thanks for the site Bob...................

zx wrote:12AU7-12BH7.............Both being vary close to the Big boy the 6SN7...may give better top on the KT90-120...well i think that's your point about the 120s in your amps...sounding good to you..

You may have run into a post of mine showing my driver collection ...



Fun rolling them in and out to suit the system. I do know that with both the Psvane KT88's and Tungsol KT120's, the top end was overly bright for my tastes. I tamed that down a LOT with a couple dampers at the primary reflection points on the ceiling AND using a sweet little triplet of Westinghouse "Star" 5963's. I also have the advantage of being able to roll tubes in my Maverick DAC to tailor the sound - that's now sporting a Tesla 6CC42 that was also quite bright with other drivers in the amp, but works real well with the current set. All working well enough that I haven't rolled a tube in several months now.

And ya ... the KT120's are exceptional in this amp, but ... long as I'm looking for another set, might as well see what's out there. Truth be told, I' kinda sorta leaning towards the Penta Labs KT88's at this point. People who got em seem to like em.

Penta Labs KT88's .....had 4ea here new...for two weeks...in a VTL amp i retube for a guy...
Look an sounded good....but not better than my standby sovtek,ys...$200.for KT88...not...
But hay thats me....
i may go for the KT120s.....but i know you have 120s....but i well get the golden gate KT88s..just for fun....i got a lot of tubes here....thay wont die....i run that 480B+...by the way what your heaters runing in you amps..........outputs tube can run a littel hot 6.5-7....but inputs should not be over 6. for the best sound ...if i run the above 6.2-3....that all seam to get briter....hhscott runs there input tube at 5.5-7 DC.....best sound ever....to me anyway


Thanks for the site Bob.....................

sKiZo wrote:Good info ... nice to see a "real world" review. Also impressed with the EXACT matching based on the box stickers ...

Just for everyone's info - those tubes will not match perfectly once installed as the components in the amp are not EXACTLY matched...

Once tubes are matched within a reasonable tolerance there is nothing else to be gained by getting a closer match in all but a VERY few cases. What is more important is how the matching was done:

1. Was the tube run-in for a significant length of time to minimize the amount of drift that occurs after the tube is placed in service?

2. Was the tube matched at voltages/currents like those the tube will see in real world service? And while it was good and hot?

3. Was the tube checked for excess screen current draw?

4. Since most gear requires measuring cathode current - not just screen current - to set bias, was the tube matched according to cathode current (not just plate current!)?

Those are FAR more important to the purchaser than "exact matching", especially if the exact matching was of the plate current only instead of cathode current.

Just a heads up ... I pulled the trigger on a factory matched set of TAD's.



Tube Amp Doctor KT88-STR Vacuum Tube

The latest version of our TAD KT88-STR is built in the style of the early British MOV KT88. It has the same big and heavy glass envelope and beautifully polished metal base. Its wonderful tone and great appearance make this tube the most attractive choice for high-end audio applications and powerful bass guitar amps.

It offers a vivid and three-dimensional tone, pleasingly warm, detailed and with subtle highs. A very musical reaction, with great sound and finest details in mids and top-end; a linear and harmonious overall response with a very natural tone, make the TAD KT88-STR our favorite tube in the KT88 and 6550A class.

I'll let you know how far I got my heads up my rear when I get them installed.  

sKiZo....
I would like to know your thinking on the diff in sound if any.....in the KT120s....an any other kt88 you may have....i dont use Chokes in my tube amps are preamps B+s any more.... i know you have a upgreaded one for two ch in your Amp....What is the B+ in your amp befor an after the choke??......
thanks for any an all input on the sound...





Thanks for the site Bob............Miss Bob.... is he bizzy or just haveing fun??

Jim McShane wrote:

sKiZo wrote:Good info ... nice to see a "real world" review. Also impressed with the EXACT matching based on the box stickers ...

Just for everyone's info - those tubes will not match perfectly once installed as the components in the amp are not EXACTLY matched...

Once tubes are matched within a reasonable tolerance there is nothing else to be gained by getting a closer match in all but a VERY few cases. What is more important is how the matching was done:

1. Was the tube run-in for a significant length of time to minimize the amount of drift that occurs after the tube is placed in service?

2. Was the tube matched at voltages/currents like those the tube will see in real world service? And while it was good and hot?

3. Was the tube checked for excess screen current draw?

4. Since most gear requires measuring cathode current - not just screen current - to set bias, was the tube matched according to cathode current (not just plate current!)?

Those are FAR more important to the purchaser than "exact matching", especially if the exact matching was of the plate current only instead of cathode current.

Hey Jim, in my experience, a lot of tube sellers are not using the right equipment for testing and are essentially selling random tubes.  

I see on your website...

When we match tubes, we are most interested in how the tube "idles" or draws current.

You cannot effectively match power tubes on a typical tube tester. Tube testers never applied the amount of voltage necessary to get accurate measurements of power tubes. In fact, there are only a couple very rare models that will allow you to get close to the voltages needed and allow you to read the parameters correctly. We use custom-built testing equipment that is the best in the business. We burn in and test power tubes at real voltages, and we test them for shorts, grid leakage, and excessive current draw before and after burn in to help minimize the chances of using your amp as a tube tester.

I did buy a set of Tung Sol 6550s from you and they've been fantastic sounding.  

Are you familiar with Roger Modjeski's RAM Labs tubes and his testing / selection techniques?  Here's what he writes about the subject...

My experience gained from testing thousands of EL-34's, 6550's, KT-88's, and other tubes has produced a wide bell curve of the two most important parameters, Bias and Transconductance. The center of this curve is the "bogey" value that the manufacturer is trying to hit, and the ends show the cutoff points of what he is willing to allow out of the factory. The tubes at the ends are still perfectly functional, but may not work well in all amplifiers, and will certainly not work well if mated with another from the opposite end of the curve.

Some amplifiers do not have enough range on the bias pots to handle the range of tubes so that selection-must be made from a particular part of the curve to ever achieve bias.

In the "good old days," I'm told, the spread of values was much less, allowing reasonable performance with random selection. Today, random selection is strongly not recommended

(Edited for misquote correction)