Ampeg rewire 7591 to accept 6L6's

[tuberattler]

I have an Ampeg Superbreverb (R-15-R) and got it with the wrong tubes in it. So I thought that instead of buying the 7591's since I have an abundance of 6L6's I'd just rewire the sockets.

Anyone have this experience or know which pins to re-wire?

[steve]

Here are some instructions from the Triode Electronics site:

http://www.triodeel.com/7591.htm

YMMV, I've never personally done this.

steve

I have an Ampeg Superbreverb (R-15-R) and got it with the wrong tubes in it. So I thought that instead of buying the 7591's since I have an abundance of 6L6's I'd just rewire the sockets.

Anyone have this experience or know which pins to re-wire?

[stokes]

I have done it to a couple of Ampegs,I didnt use these instructions,I just used the pinout guides from a tube manual and tweaked the cathode resistor to bias the tubes properly.It works just fine.When you say the amp"had the wrong tubes in it",if the amp was used with 6L6's when it was still wired for the 7591's I would suggest making sure nothing else was damaged in the amp.

[J Martin]

It will sound better with 7591 tubes. Years ago I rewired two of my Ampegs for 6L6 tubes when 7591's were rare and expensive. When they became available again I changed the amps back again. Much better.

[Rob Mercure]

Rattler,

I have to agree with J. Martin and recommend against retubing with any of the 6L6 "family" of tubes. This will alter the sound - darker with less detail. The 6L6 metal was the first beam power tube designed in the late 1930s and still a great "workhorse" in all of it's manifestations. But the 7591 is a mid/late 1950s design specifically designed for HiFi audio and I suspect that this is why the original Ampeg company chose it. While I have not experience with the current production 7591s, although I seen great reports, their existence has "stabilized" the price of NOS 7591s making these more affordable. With the current production I haven't checked prices lately but I hope you are aware that the very same identical "guts" that went into the 7591 were also packaged as the 7868 and the 6GM5. For a while these were almost as expensive as NOS 7591s but I wonder if the price has dropped now that the 7591 is in production? If so, since you were already contemplating redoing sockets, you might be able to pick up a "lifetime supply" of one of these and adapt your amp to that equivalent tube.

Rob

[Snapcase]

Hey guys, nice to know this. My main concern about using 6L6 instead of 7591 is losing the wonderful and detailed tone my Gemini already has. It seems the only way to go are expensive 7591 NOS.

[Enzo]

And if you want to experiment in a non permanent fashion, buy a couple of the 7591/6L6 plug in adaptors. A little thing you plug into the socket (kinda like a bias probe) and then plug the 6L6 into the thing. That way you can switch back and forth easily.

[Snapcase]

Thanks, Enzo. Didn't know that adapters were available. This could be great to aviod the mess or wiring and rewiring sockets back and forth to experiment with different tubes in a while. I'll need to use that things with the chassis outside the cabinet. There's only room for the 6L6GA for just a tiny margin. No room for anything else. But will be worthwhile anyway.

[Snapcase]

Errrmm... Where those adaptors could be found? I googled and didn't find them.

[Enzo]

Gee, i don't know now, they used to sell them. I was thinking Magic and AES/CEDist. Maybe they quit making them. I'll see what I can find.

[slowhand401]

Snapcase, get some J/J (telsa) 7591's and leave your amp like it is. it will sound better and have more resale value..... You can get them on ebay for about $65.00 a matched quad, and that will give you a matched pair for a back-up, without having to re-bias your amp.... Randy

[JJGross]

They sell under a couple names by different manufacturers.
Yellowjackets are one company selling tube convertors.
The other is Groove Tubes and they are called Substi-Tubes.
I use the Substitubes in my Fender HRDx to run it on EL84 power tubes. Makes a world of difference in that amp, I'll likely never put the 6L6GC bottles back in there. Now I have Fender clean and Vox/Marshall grunt.

Cheers,
- JJ

[mant]

i have a couple of gemini's.
i had a gig on a late nite tv show once and had to rent
a gemini in nyc.
i just could not dial the thing in for the life of me.
it wasn't acting like my good old trusted friends back home.
i spun the thing around to see what was going on in there and low and behold it had 6L6's in it.
it was kinda dark and barky.
couldn't get it to sit right.
either to bright in a shitty way or dull.
anyways thats my story.
7591's are the sound of that amp.