Welcome To the Hoffman Amplifiers Forum

September 06, 2025, 12:47:09 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: National Deluxe schematic  (Read 2872 times)

0 Members and 1 Guest are viewing this topic.

Offline isaac_teller

  • Level 2
  • **
  • Posts: 167
  • I love tube amps
Hoffman Amps Forum image
National Deluxe schematic
« on: October 31, 2023, 12:47:54 pm »
Hello. Is it reasonable that the volume and tone potentiometers would have such relatively low values? wouldn't 500K be about right? I'm building a clone with a few additions(master volume, grid stops on input and screen grids, capacitor and cap on input triode).


https://el34world.com/charts/Schematics/files/Valco/National_deluxe.jpg

Offline PRR

  • Level 5
  • *******
  • Posts: 17082
  • Maine USA
Hoffman Amps Forum image
Re: National Deluxe schematic
« Reply #1 on: October 31, 2023, 02:10:28 pm »
It's odd. It's not broken.

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: National Deluxe schematic
« Reply #2 on: October 31, 2023, 02:26:27 pm »
capacitor and cap on input triode
Huh? Did you mean cap and resistor? That .05 cap and 6.8M resistor are necessary for proper grid leak bias. I think adding a grid stopper on the input triode is not worth the effort.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline isaac_teller

  • Level 2
  • **
  • Posts: 167
  • I love tube amps
Hoffman Amps Forum image
Re: National Deluxe schematic
« Reply #3 on: October 31, 2023, 04:27:34 pm »
My mistake. I meant cap and resistor on the cathode of the first triode and removing the .05 cap and 6M8 resistor.

Offline ALBATROS1234

  • Level 2
  • **
  • Posts: 484
  • I love Tube amps
Hoffman Amps Forum image
Re: National Deluxe schematic
« Reply #4 on: November 30, 2023, 10:14:43 am »
Man, you must have some sag on those 6L6's with a 6X5. I wonder why they used that rectifier? I get maybe they wanted to skip out of the extra 5v winding but there are better 6V rectifiers that supply more ample current.

Offline ALBATROS1234

  • Level 2
  • **
  • Posts: 484
  • I love Tube amps
Hoffman Amps Forum image
Re: National Deluxe schematic
« Reply #5 on: November 30, 2023, 10:20:13 am »
I just saw you are building a clone. If you have the current available try a 6AX5, same pin out as the 6X5 but a much more robust rectifier. My latest build the PT and chassis came from a 1954 Revere R2R which used a 6X5 I was a little worried the PT might get hot with a 6AX5 so I bought a $15, 6.3v @ 1.5a trannie and let the PT just power the filaments for everything but the 6AX5 and used the small filament transformer just for the 6AX5. Works like a charm.

 


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