Fender Twin Reverb 65 Reissue 6L6 Tube Replacement

[TomCarlos]

Friends...

I just picked up a Fender Twin Reverb 65 Reissue amp - very clean - $600. The owner said it had a bad tube and that was causing the non-functioning Tremolo and thus the low price. Nope, it was a bad foot switch- Score one for me.

However, the amp does need a 12AT7 and two 12AX7s- I've got those.

For the Power Tubes (which are supposedly original), I pulled out Fender Groove Tubes GT6L6B. I am guessing this amp is 10 years old. But even back then, I thought the amp came with 6L6GC tubes- that is what the schematic shows. I am guessing someone swapped the tubes, maybe the owner. No biggie... I intended to replace them anyway.

So.. for the replacement... I was thinking I just use a set of JJ 6L6GC quad set.

Anyone have any other recommendations for this amp?

Thanks,

Tom

[Tom Phillips]

Hi Tom,
I'm sure you will receive many opinions. If I was replacing the tubes I would use a set of Ruby Tube 6L6GCMSTRs. A significant factor in my choice is that the pre-sale screening, matching and the warranty service offered by Magic parts is very good.
Cheers,
Tom

[TomCarlos]

Thanks! I'll look into the Ruby tubes. I see Musician's Friend is running a special on them. For testing, I dropped in an old set of JJ. The amp sounds good, even with the old tubes. The Plate voltage is 432 volts. The current through the (unmatched) tubes ranges from 37.1 to 41.5 ma. So I'm averaging around 57% dissipation? When I get a quad set, I'll reset the bias.

[g1]

GT makes up their own version of what the suffixes mean, so pay no mind. It's not really a 6L6B in the NOS sense. For instance they have a 6L6CB which the CB stands for "coke bottle". I believe the GT6L6B was pretty much a standard Sovtek 5881WXT (6n3C-E).

Here's a handy chart I hadn't seen before, shows the generic names for GT versions: Groove Tubes

[TomCarlos]

Thanks Greg.... that is a handy chart indeed.

[Tom Phillips]

...I dropped in an old set of JJ. The amp sounds good, even with the old tubes. The Plate voltage is 432 volts. The current through the (unmatched) tubes ranges from 37.1 to 41.5 ma.....

In that case I'd say you are good to go with those tubes. They sound good to you and they are matched with in ±6%. That is as well as is common with "Matched tube sets" after they get some real break in time in an amp.

[TomCarlos]

I'm outside the ±6% range. Musicians Friend is running a deal on the Ruby tubes. I ordered a set and will try those. I want to keep my JJ for another project.

[Enzo]

37.1 to 41.5 averages 39.3. That is 2.2ma either way. 2.2 away from 39.3 is under 6%. Some matched sets will be relatively close, others not as much, it varies. I don't consider 10% out of line. More importantly, these are guitar amps, not precision gear. Close is good enough.


I also think those Ruby 6L6GCMSTR are good sturdy reliable tubes. I use them more than any other.

[TomCarlos]

Thanks again Tom and Enzo!