Reissue gold lion kt66 vs JAN 6L6WGB?

Muttlyboy

Member
Messages
3,163
Hi everybody,
A good friend of mine has a re-issue Bluesbreaker and it's time for new tubes.
At one point it had a pair of Valve art kt66's that sounded good, but died quick.

The new gold lion kt66's are getting close to the price of NOS 6L6WGB's (which I haven't tried either)

I'm wondering if anyone has any experience with comparing these tubes...particularly in a jtm45 type amp.

Thanks,
Chris
 

swiveltung

Member
Messages
14,483
Well.... they are very different... the WGB is the low power than the 6L6GC design, of course the KT66 is much higher power. NOS military WGB, often Sylvania, should be very cheap, plenty around. I have noticed some sellers trying to get a lot for them though recently...
 

Tone Meister

Member
Messages
3,266
Well.... they are very different... the WGB is the low power than the 6L6GC design, of course the KT66 is much higher power. NOS military WGB, often Sylvania, should be very cheap, plenty around. I have noticed some sellers trying to get a lot for them though recently...

I believe the 6L6WGB is a 26-watt tube and a KT66 is a 25-watt tube. Not that it matters, though, because I have had more premature failures and more failures right out of the gate with Gold Lions than any other brand. If your choice is limited to just those two, the WGBs are a no-brainer, IMPE. That said, I've had excellent results with the Valve Art KT66s, including long life.
 

Vanyu

Member
Messages
738
I haven't had the best of luck with those JAN 6L6WGB's in high powered combos, the combo environment combined with the electrical limitations, IME, has simply been too much for this tube to handle. I have a customer who loves these tubes in his HRDx, but it just chews right through them about every 8 months due mostly to vibration, with heat being the next catalyst in this case, and I'd imagine a BB would be even harder on this tube. These tubes are spec's very close to a 5881, with a 400V anode limit and a 300V on the screens. Marshalls usually run much higher than this, and the vibration from the speakers won't be doing it any favors either.

With that in mind, my vote goes to the Genalex KT66. Heard nothing but good things about them.
 

swiveltung

Member
Messages
14,483
I believe the 6L6WGB is a 26-watt tube and a KT66 is a 25-watt tube. Not that it matters, though, because I have had more premature failures and more failures right out of the gate with Gold Lions than any other brand. If your choice is limited to just those two, the WGBs are a no-brainer, IMPE. That said, I've had excellent results with the Valve Art KT66s, including long life.
Yes, you are right about the KT66, my error.
 

Muttlyboy

Member
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3,163
Thanks for the replies,

Vanyu, i thought that gold lion and genelex are the same. Are they different tubes?
I was also assuming that the JAN tubes being NOS American military would be very rugged reliable tubes. I saw posted that should handle 470 volts on the plates.
Also, in the case of the Blues breaker re-issue, I think that it was 405v with the valve arts (which died a quick death)

Tone Meister, from what I've seen posted on the Web, I been led to believe that the new re-issue gold lions (same as genelex?) are a premium kt66...I guess not so much?

Swiveltung, I typically see the Sylvania wgb'so going for about 100 a pair...Not cheap, but if actually are a long lasting tube, not a bad deal at all

So far no one seems to be in agreement...
I'm hoping to get a concensus
 

sickboy79

Member
Messages
14,241
I can't speak for the Gold Lion KT66 (the one you can buy today is a new production tube made in the Sovtek/Reflektor factor (probably spelled that wrong). I LOVE JAN Philips 6L6WGBs. My favorite 6L6 tube of all time. I'm running them in many amps, including a 62 Blonde Bassman with 480v on the plates. Zero problems. I've heard numerous sources say they can easily take 500v on the plates. Not sure about the screens. Just bias them as a 23-25w tube. Lower headroom and amazing midrange. Highly recommended.
 

swiveltung

Member
Messages
14,483
Thanks for the replies,

Vanyu, i thought that gold lion and genelex are the same. Are they different tubes?
I was also assuming that the JAN tubes being NOS American military would be very rugged reliable tubes. I saw posted that should handle 470 volts on the plates.
Also, in the case of the Blues breaker re-issue, I think that it was 405v with the valve arts (which died a quick death)

Tone Meister, from what I've seen posted on the Web, I been led to believe that the new re-issue gold lions (same as genelex?) are a premium kt66...I guess not so much?

Swiveltung, I typically see the Sylvania wgb'so going for about 100 a pair...Not cheap, but if actually are a long lasting tube, not a bad deal at all

So far no one seems to be in agreement...
I'm hoping to get a concensus
Yep, the current pricing amazes me, I just checked. Dumbfounded actually. I guess I better polish the ones I've got out there and find the boxes ... :>)
 

Vanyu

Member
Messages
738
Genalex is easier to type than Gold Lion lol, they're the same tube. Genalex is just the brand name.

Of course, your mileage may vary, but personally, based off of what I've experienced, I wouldn't put these tubes anywhere you wouldn't put a 5881. I don't know my customer's playing habits, but he finds a way to plow through those tubes. On that topic too, I have another customer who manages to plow through about a set of old Tung Sol 5881's a year, coincidentally also a combo. You really won't know what will happen until you do it.

Definitely check your screen voltage, having a low (but still in spec) screen voltage will go a long ways in preserving a tubes life. IME, the screen voltage seems to be more sensitive than plate voltages. Musicman ran upwards of 700V on the plates of 6L6's with good results, and even higher on 6CA7's, but had a very low screen voltage at around 350V IIRC. Don't be afraid to increase values to whatever necessary. Fusionbear recently did a JTM45/100 build here on the forum using either 2.2K or 3.3K on the screens with good results with a pair of KT88's with a PV of about 500V. You won't hurt anything by playing around here, and can only improve your tube life, as long as you don't go lower than 470.
 

Tone Meister

Member
Messages
3,266
... i thought that gold lion and genelex are the same. Are they different tubes?

In name only. Actually, the current "Genelex" Gold Lion are very different tubes from the Genelex of old, and it's an abomination they are able to use the same name. A set of authentic old stock Genelex KT66 will set you back a small fortune, IF you can find them. But they will also last for years. I have not had a set of Gold Lion KT66 last more than a couple of months, and that was with fairly conservative bias settings (~60% dissipation). Also bear in mind that my experiences are much different from many others who have been very satisfied with the Gold Lions.

Tone Meister, from what I've seen posted on the Web, I been led to believe that the new re-issue gold lions (same as genelex?) are a premium kt66...I guess not so much?

http://www.drtube.com/datasheets/6l6wgb-tungsol.pdf

They are indeed a premium KT66, but my own experiences don't bear that out. Between those two choices the WGB is the way to go. They are a 26-watt tube, but many very reputable sources claim they can be biased as 30-watt tubes and handle plate voltages in the 470-500 volt range.
 

hacinador

Member
Messages
764
Can the Bluesbreaker Ri run KT66s? I would'n be so sure about it. These tubes have much higher current draw compared to 6L6 or EL34. Is the PT strong enough for this??? There are also differences about impedance ratio for the output transformer...
 

Muttlyboy

Member
Messages
3,163
Can the Bluesbreaker Ri run KT66s? I would'n be so sure about it. These tubes have much higher current draw compared to 6L6 or EL34. Is the PT strong enough for this??? There are also differences about impedance ratio for the output transformer...
Back when I first set this amp up (over 10 years ago) it was with a Metro amp jtm 45 board kit which came with the Valve art kt66 tubes.

At the time there was several sites and forums explaining how to do the conversion.
If I remember right, the main concern for the tube swap (the amp came with Sovtek5881's stock) was to increase the screen resistors to 1k. (maybe also the bias resister value)

In thinking about it, maybe those kt66's pulled down the voltage to 405v, but when I first did the installation of the kit, It probably never occurred to me to check voltages before and after. I just would have checked voltages to compare to the kit instructions.

Anyway, I gave that amp away to a good friend of mine, and not to long after that the tubes failed, so he had a tech near him make the repairs and the Sovtek tubes went back in.
 
Last edited:

Vanyu

Member
Messages
738
Back when I first set this amp up (over 10 years ago) it was with a Metro amp jtm 45 board kit which came with the Valve art kt66 tubes.

At the time there was several sites and forums explaining how to do the conversion.
If I remember right, the main concern for the tube swap (the amp came with Sovtek5881's stock) was to increase the screen resistors to 1k. (maybe also the bias resister value)

In thinking about it, maybe those kt66's pulled down the voltage to 405v, but when I first did the installation of the kit, It probably never occurred to me to check voltages before and after. I just would have checked voltages to compare to the kit instructions.

Anyway, I gave that amp away to a good friend of mine, and not to long after that the tubes failed, so he had a tech near him make the repairs and the Sovtek tubes went back in.
KT66 should be no problem. Screens should be AT LEAST 1k, regardless of tube type, and could go higher for extended tube life at the cost of a little bit of power and added compression.

I don't think a KT66 would stress the power supply and drag down the B+ by a huge amount, unless they were overbiased, of course.

(Real) 5881's are out on FeeBay on the cheap, not much different than the WGB's at all. Just something to keep an eye on, could save you a couple bucks.
 

hacinador

Member
Messages
764
One 6L6 needs about 0.9A for heaters, but "true" KT66 needs about 1.3A. In dual 6L6 you need to have a PT that can handle extra 0.8A for heaters to run a pair of KT66, extra 0.8A is quite big portion for a PT. There were some "KT66" in past that have only 0.9A per tube, they were more like 6L6s and not like "true" KT66, Tung-Sol KT66 is one of them... They can be used in 6L6 style amps without any problems with higher current draw for heaters.
 
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Advisable Owl

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I've been running the new Genelex KT66s in my JTM45 head with no problem for several months at 450 on the plates and 445 on the screens.
 

Roe

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8,752
the metro handles the heater current perfectly and even the marshall RI is likely to do ok.
 




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