New KT66 opinions

[Randall]

I have a Marshall Super 100 re-issue in for a hum issue that turns out to have a dead KT66. The other three seem OKay, the are Russian Gold Lion brand. I ordered up a new set of JJ KT66s, but the bases are so large, they won't fit into the spring clips, and I am not going to mod this amp to accommodate this. These sets are expensive at about $150/quad. Does anyone have any experience with other brands of KT66? There doesn't seem to be many choices. And also, any opinions on just replacing the dead one? The ones I have are from the Tube Store, and have their rating system of 39 on them, whatever that means. Would you trust just ordering another 39 and see if it actually matches?

[Heliotricity]

I've had JJ KT66s fail on me and at least one Gold Lion, maybe two. Tung Sols and Valve Arts have lasted for me. Some people say the TS are more 6L6 sounding, kind of KT66 with their own thing, I really liked them in my JTM45.

Is the Super 100 one of the reissues with the really high screen and plate voltages? That might be a factor, seems like I read it was either with that one or the Hendrix JTM45-100 reissue that people were having issues with modern tubes not being able to handle the voltages...

[Leo_Gnardo]

The ones I have are from the Tube Store, and have their rating system of 39 on them, whatever that means. Would you trust just ordering another 39 and see if it actually matches?

Looks like the best chance you have. What's the plate & screen grid voltages in that Marshall. Though some people seem to think the whole KT series is bulletproof, they do have their limits. I've used KT88 successfully in various 100W Marshalls, they seem to hold up well, no failures so far. Haven't used many KT66 but so far the ones I have installed in a reissue JTM45 hold up fine and are the best sounding out of several choices including NOS GE 6L6GC.

[drewl]

Can't you re-position the clips sideways to fit the tubes or bend them out slightly?

Always worked for me.

[Tone Meister]

Yes, you can order just another 39 from The Tube Store and it will match your remaining good tube.

One caveat you should know about is the metal base on the Tung Sol KT66 reissue. The metal base is tied to pin 1 and will short the bias voltage to the bear claw tube retainer. If you do decide to go with the Tung Sol KT66, you will need to change the retainers to the spring type.

http://ztalk.proboards.com/thread/27...w-tung-sol-66s



The Tung Sol "KT66s" only draw 900 mA while to my knowledge all other modern "KT66" draw 1300 mA.

I have had an inordinate number of failures with ALL Gold Lion tubes, but their KT66 seems even more fragile than any other I've tried. The Valve Arts are solid as are the Ruby and TADs - all three just test and rebrand tubes but don't actually manufacture them. The JJs sound good, but I've experienced excessive tube rattle from far too many of those to recommend them.

I would recommend these, in this order:

1) Ruby
2) TAD
3) Valve Art
4) Tung Sol

None of these are true KT66, of course.

[Tone Meister]

... Haven't used many KT66 but so far the ones I have installed in a reissue JTM45 hold up fine and are the best sounding out of several choices including NOS GE 6L6GC.

Which KT66s are you using in your JTM45 Leo_Gnardo?

[Randall]

The plate voltage is about 545 v, that was with two tubes installed. They are drawing from 49.8 mA to 52.7 mA.I spo 's whatke with a tech at Tube Store (very helpful), and he thought since these are still fairly new with not much use, and still pretty well matched I should have a pretty good chance of getting a new one to match. So that's what I did.

Let's see how long this $52 single tube takes to ship from Canada to Southwest Florida.

[Jammin'John]

I've had good luck with the Shuguang's.

JJ

[Tone Meister]

I've had good luck with the Shuguang's.

The Ruby, TAD, and Valve Art KT66s are Shuguangs that have been rigorously tested. They come with a 6 month warranty

[Jammin'John]

I run 'em in my Tweed clones & my SE amp.

JJ

[Leo_Gnardo]

Which KT66s are you using in your JTM45 Leo_Gnardo?

Whups I shoulda mentioned they were early 90's Shuggies. The amp is a customer's, his ears agreed, KT66 best in show, for his amp anyway.

545V plate Randall, and close to that on screen grids, with 50 mA, I think your friend at the tube sales desk is whistling in the graveyard. That's IMO a stretch for '66's. Sometime your customer should try a set of KT88, I really think that's a better choice. I've used EH - some problem tubes - and JJ - so far no problems. The hi fi crowd seem to adore the premium priced GEC/Genalex line marketed by New Sensor aka Sovtek/ElectroHarmonix.

I'd mention KT77 too but I find they work well in some amps & not others, it's a matter of "do you like what they sound like when heavily clipped". Not for every situation but can recommend for hifi amps, where I've used JJ successfully in Dynaco Stereo 70, MkII and MkIII. .

[Randall]

Looks like cooling off the bias on this one is in order. Every amp this customer has brought has been way hot.

[Tone Meister]

Looks like cooling off the bias on this one is in order. Every amp this customer has brought has been way hot.

How hot were those Gold Lion KT66s running? My experience is the KT66s don't really come into their own until they're dissipating about 17-18 watts, assuming a 25 watt tube.

[Randall]

I refer you to post #6. Tone Meister.

[Tone Meister]

That is hot. I wonder how long they were run that way? I'm gonna cross my fingers and hope that the rest of those Gold Lions weren't stressed too badly.