Welcome To the Hoffman Amplifiers Forum

September 08, 2025, 05:53:44 am
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Stout TMB with an octal preamp  (Read 2421 times)

0 Members and 1 Guest are viewing this topic.

Offline lvrocker

  • Level 1
  • *
  • Posts: 5
Hoffman Amps Forum image
Stout TMB with an octal preamp
« on: March 26, 2018, 06:44:31 pm »
I was thinking I'd like to build the stout tmb, but swap an octal 6SL7 preamp for one of the 12AX7s for some different tonal qualities. Anyone do this? Would I need to modify much in the circuit to accommodate this tube type? Thanks

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: Stout TMB with an octal preamp
« Reply #1 on: March 26, 2018, 06:50:41 pm »
I was thinking it would be pretty easy to do.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline shooter

  • Level 5
  • *******
  • Posts: 11015
  • Karma Loves haters
Hoffman Amps Forum image
Re: Stout TMB with an octal preamp
« Reply #2 on: March 27, 2018, 09:40:43 am »
no 6SL7, 6SN7 examples, fwiw
Went Class C for efficiency

Offline 92Volts

  • Level 2
  • **
  • Posts: 385
  • I love Tube amps
Hoffman Amps Forum image
Re: Stout TMB with an octal preamp
« Reply #3 on: March 27, 2018, 11:32:00 am »
GE datasheets have charts giving gain and clean signal numbers for different configurations of a tube (voltage, plate and cathode resistance).

If you wanted you could tweak values to make the 6SL7 perform closer to the original tube in the original circuit.

Or just assume 6SL7=12AX7 and 6SN7=12AU7, like most people do, and see how it sounds. They're certainly close enough to function in the same circuits, with slightly different gain and response depending how they're loaded by the following stage.

Offline lvrocker

  • Level 1
  • *
  • Posts: 5
Hoffman Amps Forum image
Re: Stout TMB with an octal preamp
« Reply #4 on: March 27, 2018, 11:45:06 am »
Shooter, thanks for the schem.
92Volts I suppose tweaking the voltages where they should be for the 6SL7 is key, I'd still use the other 12ax7 as the PI, tinker around a bit with things, I did read somewhere that swapping the 6SL7 straight into the circuit would be close enough without much change, but I think it'll be a fun build either way.

 


Choose a link from the
Hoffman Amplifiers parts catalog
Mobile Device
Catalog Link
Yard Sale
Discontinued
Misc. Hardware
What's New Board Building
 Parts
Amp trim
Handles
Lamps
Diodes
Hoffman Turret
 Boards
Channel
Switching
Resistors Fender Eyelet
 Boards
Screws/Nuts
Washers
Jacks/Plugs
Connectors
Misc Eyelet
Boards
Tools
Capacitors Custom Boards
Tubes
Valves
Pots
Knobs
Fuses/Cords Chassis
Tube
Sockets
Switches Wire
Cable


Handy Links
Tube Amp Library
Tube Amp
Schematics library
Design a custom Eyelet or
Turret Board
DIY Layout Creator
File analyzer program
DIY Layout Creator
File library
Transformer Wiring
Diagrams
Hoffmanamps
Facebook page
Hoffman Amplifiers
Discount Program