Re-tubing a twin reverb

Re-tubing a twin reverb

Postby Poor Peter » Wed Apr 30, 2014 3:01 pm

Howdy all, I'm sure this topic exists somewhere in the depths of this forum so I apologize in advance. I'm picking up a used TR. The guy I'm buying it from (a good friend that I trust) tells me it needs new tubes and to be biased. He told me to let him know what kind of tubes I want and he will order them and get it set up. I have a Super Reverb now with JJ's in it, but there is very little headroom. I know that is probably more to do with the amp than the tubes. At least thats what I've been told. I am hoping some kind folks could chime in and tell me what they recommend or what they use in a TR. As always thanks.
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Re: Re-tubing a twin reverb

Postby caspersvapors » Wed Apr 30, 2014 3:44 pm

if you can get SED Winged C 6L6's I highly recommend those. Also NOS tubes are not overrated! I like a GE long plate 12ax7 for my reverb/vibrato channel and a NOS JAN Phillips 12at7 for my reverb driver
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Re: Re-tubing a twin reverb

Postby caspersvapors » Wed Apr 30, 2014 3:46 pm

Poor Peter wrote:Howdy all, I'm sure this topic exists somewhere in the depths of this forum so I apologize in advance. I'm picking up a used TR. The guy I'm buying it from (a good friend that I trust) tells me it needs new tubes and to be biased. He told me to let him know what kind of tubes I want and he will order them and get it set up. I have a Super Reverb now with JJ's in it, but there is very little headroom. I know that is probably more to do with the amp than the tubes. At least thats what I've been told. I am hoping some kind folks could chime in and tell me what they recommend or what they use in a TR. As always thanks.


a Super Reverb with JJs and very little headroom? At what point on the volume does it start to breakup? My pro reverb is REALLY freakin loud by the time it breaks up
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Re: Re-tubing a twin reverb

Postby Poor Peter » Wed Apr 30, 2014 4:11 pm

caspersvapors wrote:
Poor Peter wrote:Howdy all, I'm sure this topic exists somewhere in the depths of this forum so I apologize in advance. I'm picking up a used TR. The guy I'm buying it from (a good friend that I trust) tells me it needs new tubes and to be biased. He told me to let him know what kind of tubes I want and he will order them and get it set up. I have a Super Reverb now with JJ's in it, but there is very little headroom. I know that is probably more to do with the amp than the tubes. At least thats what I've been told. I am hoping some kind folks could chime in and tell me what they recommend or what they use in a TR. As always thanks.


a Super Reverb with JJs and very little headroom? At what point on the volume does it start to breakup? My pro reverb is REALLY freakin loud by the time it breaks up


My SR starts to break up around 4. When everything is mic'd and I have my own monitor I can keep it around 3.5 and it works pretty well. Unfortunately those circumstances aren't always there and anytime we get outside by midset I've had to crank it up to around 4.5 or even 5. I know, tell your drummer to keep it in his pants and you won't have to worry about it, but that's a whole different thread.
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Re: Re-tubing a twin reverb

Postby zambiland » Wed Apr 30, 2014 5:30 pm

The ultimate in clean headroom and the tubes that the GD used back in the day are the Philips 7581As. They would buy them by the pallet from military auctions. Not only can they produce more power than a garden variety 6L6, they are also rated for many more hours MTBF (5000). I managed to snag 2 quads, one for my MC30s and one for my Showman. I'm not sure how well the reissue does as I haven't tried them yet. And probably won't have to for years.
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Re: Re-tubing a twin reverb

Postby Searing75 » Thu May 01, 2014 5:50 am

7581'a are great for sky high headroom! I have tried many, and my favorite in my Twin were the Winged C's for power, and it was a crap shoot for the preamp tubes. NOS Mullard 12AT7's are great. I like the Shuguang 12AX7's a lot. Try as many different 12AX7's as you can. They vary so much, even from the same factory!

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Re: Re-tubing a twin reverb

Postby Smolder » Thu May 01, 2014 6:55 am

Well, I don't need huge amounts of volume and for the level I play the huge headroom becomes a bit of a problem. I rarely play in stadiums or if it's a large room the guitar amps should be mic'd and run through the PA. In fact... I run my twin with only two power tubes and generally only one of the speakers (so that the impedance is matched).

I really like GE clear tops and RCA blackplates. They each sound a bit different. They will set you back some coin, but in the long run they will last a lot longer and you'll save money (like over 6-10 years of playing). Either Mike @ kcanostubes.com or Gregg at hitestguitars.com probably still have NOS in stock.
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Re: Re-tubing a twin reverb

Postby tatittle » Thu May 01, 2014 10:29 am

I am wondering if you have the right impedance load on your Super Reverb. I think it is a 2 ohm OT. If the 4 speakers are not wired correctly you could end up with a 32 ohm load which will significantly decrease headroom. I believe standard for SR's: 2 sets of 2 speakers wired in parallel so if 8 ohm speakers: 2 x 8ohm (4ohm) + 2 x 8 ohm (4ohm) = 2ohm total.

That said, I think the reverb Fenders do BEGIN to break up around 4-5 volume in general. Twin is higher though.
Last edited by tatittle on Thu May 01, 2014 10:34 am, edited 2 times in total.
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Re: Re-tubing a twin reverb

Postby tatittle » Thu May 01, 2014 10:29 am

I am wondering if you have the right impedance load on your Super Reverb. I think it is a 2 ohm OT. If the 4 speakers are not wired correctly you could end up with a 32 ohm load which will significantly decrease headroom. I believe standard for SR's: 2 sets of 2 speakers wired in parallel so if 8 ohm speakers: 2 x 8ohm (4ohm) + 2 x 8 ohm (4ohm) = 2ohm total.
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Re: Re-tubing a twin reverb

Postby Poor Peter » Thu May 01, 2014 5:38 pm

tatittle wrote:I am wondering if you have the right impedance load on your Super Reverb. I think it is a 2 ohm OT. If the 4 speakers are not wired correctly you could end up with a 32 ohm load which will significantly decrease headroom. I believe standard for SR's: 2 sets of 2 speakers wired in parallel so if 8 ohm speakers: 2 x 8ohm (4ohm) + 2 x 8 ohm (4ohm) = 2ohm total.


If they're not then it came from the factory that way. I haven't done anything to it since I bought it aside from tubes and biasing. Thanks to all who responded. You've given me a lot to chew on.
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Re: Re-tubing a twin reverb

Postby tatittle » Thu May 08, 2014 7:50 am

If it came new it is probably wired correctly yes. But stranger things have happened. If you buy a $5. multimeter you can easily check a lot of the basic specs. yourself--more as maintainence vs. actual mods and repairs (which require more technical know-how). In this case you would just set the meter to read ohms (at lowest setting probably) and measure the 1/4' speaker plug where it feeds into the chassis jack.
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