I found some old 7591A Tubes - Can I put them in an amp to replace 6L6's?

[3NSDan]

Hi everyone,

I've been searching the internet, and have not been able to come across a straight answer for this one. My Grandpop recently passed away, and I always knew he had some old amps down in the basement. I came across an Ampeg Gemini that he seems to had given up working on sometime between 1968 and 2007

He had the tube sockets marked "12ax7" and "6L6". Well, knowing that vintage 6L6's might well sound unbelievably great, I grabbed them and took them home. Upon further inspection, the tubes are actually Sylvania made 7591A's.

My question is, can I try them in my Marshall or Boogie that has 6L6's, or would I need some sort of adapter to do that?

Thanks for any information,

-3NSDan

[CitizenCain]

No can do on trying them out in an amp wired for 6L6 tubes (or 6V6 or EL34, 6550, KT88, etc). The pinout on the 7591 is different than the 6L6 and it won't work. I don't know of anyone who sells adapters for that pairing.

[3NSDan]

Thanks CitizenCain, that's what I figured. Maybe I'll slap those back in the Gemini and see if I can't get that to work after all.

-3NSDan

[custom_amp_30]

7581 = 6L6
7581A = 6L6G
At least thats what my Tube sub book states and there was not a sub for that 7591.

[Baxtercat]

Folks want 7591's [scarce!].
Sell 'em!

[trevorus]

Get that Gemini fixed and play that thing!

[Jefflom]

would you be interested in selling one of the 7591 tubes?

[Enzo]

Fellows, please keep in mind that the 7581 and 7591 are not the same.

The pinouts for the 6L6GC and friends are not at all similar to this. So the question becomes has the coversion wiring already taken place. And for that matter, if converted already, was it done correctly?

[harojs]

7591s

Let me know if you'd like to sell those 7591s. -J

[Gtr_tech]

The 7581a is a beefy 6L6....industrial grade. The 7591a is a smaller pwr tube specially designed for audio...about the physical size of a 6V6. The 2 are not even *remotely* compatible. Check the socket wiring for verification.

[Gtr_tech]

And FWIW, the Gemini II and 22 used the 6L6, while the regular Gemini and Gemini IV used the 7591. Check before throwing the switch....

[Gtr_tech]

Dammit...I just realized this thread is way necro. That makes twice this week......

[hrbay]

Feel you pain....bumping resting horses. The 7591/A were only used in large numbers by mid-high end audio hi-fi makers like Scott, Fisher and Mcintosh I think. Not much to do with geetar anyways. Powerful little tube though.

[Gtr_tech]

Well actually 7591s are quite common in alot of Ampeg, Gibson, and other misc. amps. Also pretty common in organ amps as well.

[Chuck H]

Supposedly a great tube for guitar amps and OD's fabulous. I've never had the pleasure, but... I did use the OT from a Fisher 500B (2x7591a per channel) in a build. I'm thinking of having that OT cloned, it sounds so good with 6l6's or el34's (6.6k primary Z). I should really try it with actual 7591A's too... But they're all in Japan?!? Other than the reissue variety. Which I've read is just a repackaged 6L6.