Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: imgumby001 on March 17, 2023, 04:14:14 pm

Title: 7591 PP Circuit Recommendations
Post by: imgumby001 on March 17, 2023, 04:14:14 pm

Hello all,

 I’ve got some 7591’s laying around and a good PT w/a pp OT(from a Lowrey organ). Are there any circuits you all would recommend taking a look at to base a build on?

Thank you,

NR

Title: Re: 7591 PP Circuit Recommendations
Post by: sluckey on March 17, 2023, 05:06:17 pm

Look at the Ampeg G12, M12, or R12 series. Probably other Ampegs use the 7591 too.

     https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_Schematics.htm

Title: Re: 7591 PP Circuit Recommendations
Post by: dude on March 17, 2023, 05:11:28 pm

That tube makes a nice SE amp, many schematics for SE amps, just change the socket wiring.

Title: Re: 7591 PP Circuit Recommendations
Post by: imgumby001 on March 17, 2023, 06:31:07 pm

Awesome!! Thank you gentlemen.

Title: Re: 7591 PP Circuit Recommendations
Post by: SoundmasterG on March 23, 2023, 12:36:09 am

Ampeg usually ran the screens quite lower than the plates which limited the power. If you run them up along where Fender might have used them in comparison to the plate voltage, you can get more power (and tone) out of the 7591's. Make sure your OT can handle the power though. The 7591 is a sensitive tube for a power tube, and they don't need a lot of gain in front of them to push them, similar to a 6BQ5/EL84. The 7591/7868 is my favorite tube to use as it has decent power, can be made to really sound good without much effort, yet has a more full bass response than the often lacking 6BQ5/EL84 does. It's too bad no one ever made a version with the same pinout as the 6L6 and 6V6 as it sits right between them for power and tone.


Greg

Title: Re: 7591 PP Circuit Recommendations
Post by: AmberB on March 25, 2023, 07:43:12 pm

Another circuit design you might want to look at for the 7591s is the various Bogan Challenger amps.  They use 7868s, but it's basically the same tube as the 7591, just with a different base.  The Bogan CHB-35 is probably the best schematic to look at for the output section.  Lots of those amps have been modified for guitar use, so if you're starting from scratch, you can basically use the Ampeg Gemini preamp and the Bogan CHB-35 power amp sections together.  I think there's at least a couple schematics for modified Bogans here in the schematic section.
I've modified several of the CHB-35s, they sound good and get plenty loud!

Title: Re: 7591 PP Circuit Recommendations
Post by: Sonny ReVerb on March 27, 2023, 07:24:31 pm

Give this one a look see:

https://el34world.com/Forum/index.php?topic=23894.msg257236#msg257236