1975 Twin Reverb - Which tubes?

[Whitey-on-the-moon]

I've just purchased a 1975 Fender Twin which is currently in service and my amp tech has highly recommended the 6L6GC groove tubes to replace the still original Fender tubes.

Does anyone have any experience of this upgrade in a silverface twin?
Is it worth the extra cash over a standard Svetlana replacement?
What would the differences be?

I've looked at the groove tubes website and can't find 6L6GC but there is a 6L6GE. Are they the same tubes or is one the reissue of the other? I'm confused so if anyone can shed some light on this I'd be greatful.

Thanks!

[ahamay79]

Don't wast your money on Groove Tubes. They are just rebranded Sovteks, JJ's, and other tubes. And the Groove Tube 6L6GE is a 6L6GC.... the "GE" stand for "General Electric". It's a copy of a GE tube design.

The Sovtek 6L6WXT+ is a good tube, as is the JJ 6L6GC, and the Svetlana 6L6GC. I use these all the time.

[Gtr_tech]

The WXT+ is a nice sounding tube, but they won't hold up in an ultralinear design. Some 70s Twins were UL, so verify which version you have there before you try that one.

[bnwitt]

I would choose the Winged C 6L6GC tubes over any other brand for that amp. Forget the Groove tubes. Also, Svetlana tubes in America are not really Svetlana tubes. The owner of Electro Harmonix purchased that brand name when it's American registration expired, much to the chagrin of the real Svetlana company. The real Svetlana company can no longer use their own name in the states, only in Europe and other countries. If you go to the sovtek site and look at the Svetlana tubes they sell you will see "No shipments to EU" for them. He cannot ship them their as he would be violating their licensed brand in Europe since they still hold the license there.

He also purchased the Mullard and the Genelex gold lion names. He is rebranding his sovtek tubes (he owns that plant in Russia) with the purchased brand names which IMHO is deceptive. The real Svetlana tubes are now called "winged C" in the states. IMHO the winged c are the best 6L6GC tubes currently made. They not only sound great, but are very reliable. After installing literally hundreds of them I have only had one individual tube prematurely fail. Very high quality.

[Whitey-on-the-moon]

I would choose the Winged C 6L6GC tubes over any other brand for that amp. Forget the Groove tubes. Also, Svetlana tubes in America are not really Svetlana tubes. The owner of Electro Harmonix purchased that brand name when it's American registration expired, much to the chagrin of the real Svetlana company. The real Svetlana company can no longer use their own name in the states, only in Europe and other countries. If you go to the sovtek site and look at the Svetlana tubes they sell you will see "No shipments to EU" for them. He cannot ship them their as he would be violating their licensed brand in Europe since they still hold the license there.

He also purchased the Mullard and the Genelex gold lion names. He is rebranding his sovtek tubes (he owns that plant in Russia) with the purchased brand names which IMHO is deceptive. The real Svetlana tubes are now called "winged C" in the states. IMHO the winged c are the best 6L6GC tubes currently made. They not only sound great, but are very reliable. After installing literally hundreds of them I have only had one individual tube prematurely fail. Very high quality.

Thanks for the recommendation! I'm in the uk so I guess I'll be going for the Svetlana 6L6GC. I did wonder why it stated on the website that they don't provide a service for visitors from the US or Canada. So my mind is made up anyway the Svetlanas it is.

Thanks again!

[ahamay79]

I don't know I forgot to mention the Winged C's. Great tubes. I love the EL34's.

[ctcpete]

I've also got a 75 or 74 Twin 100W. I've already bought JJ tubes. Any opinions on JJ's?

I'm still using the old 5881 Sovtek power tubes that where in it while I refurb and blackface the amp. I hope at least that the JJ 6l6's will be an improvement on the 5881's. The pre amp tubes are all RCA's I assume are originals. They seem to work fine.

[Diablo]

Make sure the tech gives you back your original tubes. They're probably worth more than any new production tubes he will stick in your amp. I've got original RCA power tubes in my V4, and they simply don't make 'em like they used to.

[Whitey-on-the-moon]

Make sure the tech gives you back your original tubes. They're probably worth more than any new production tubes he will stick in your amp. I've got original RCA power tubes in my V4, and they simply don't make 'em like they used to.

Cheers for the hint. It's actually somthing I'd considered but then I thought 'why would old worn out tubes be worth anything?'

I will ask him for them back though as they do have fender written on them but is there some market for worn out tubes that I'm unaware of?

[ctcpete]

Actually, thanks to this forum and much other info on the web, I've been doing the work myself (I do have a tech background in the printing industry).

From what I have heard (remember I am a novice with tube amps), the power tubes frequently fail before the pre amp tubes. The pre amp tubes may still be good, mine seem to be.

Whitey, You may want your tech to modify the amp so the bias is adjustable. These old Twins had a Hum Balance adjustment but not a true bias adjustment. An additional trim pot can be added so you will have a bias adjust as well as a balance adjust capability. Or you can change the connections on the hum pot to make it a bias adjust pot. There is a recent thread on this forum on this subject.

[Jim Darr]

Are you sure all the tubes need replacing? Just because they are old doesn’t necessarily mean they are bad. Have them tested if you can.

Jim

[Whitey-on-the-moon]

Actually, thanks to this forum and much other info on the web, I've been doing the work myself (I do have a tech background in the printing industry).

From what I have heard (remember I am a novice with tube amps), the power tubes frequently fail before the pre amp tubes. The pre amp tubes may still be good, mine seem to be.

Whitey, You may want your tech to modify the amp so the bias is adjustable. These old Twins had a Hum Balance adjustment but not a true bias adjustment. An additional trim pot can be added so you will have a bias adjust as well as a balance adjust capability. Or you can change the connections on the hum pot to make it a bias adjust pot. There is a recent thread on this forum on this subject.

I've already got him looking into the tube bias mod. If it prolongs the life of the tubes then I'm all for it!

[Whitey-on-the-moon]

Are you sure all the tubes need replacing? Just because they are old doesn’t necessarily mean they are bad. Have them tested if you can.

Jim

He's got a tube tester and he's an honest guy so I know he won't replace them if they don't need to be.