Welcome To the Hoffman Amplifiers Forum

September 08, 2025, 02:26:31 am
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Vibro champ ? Switch on intensity pot  (Read 2449 times)

0 Members and 1 Guest are viewing this topic.

Offline fred

  • Level 1
  • *
  • Posts: 10
  • I love Tube amps
Hoffman Amps Forum image
Vibro champ ? Switch on intensity pot
« on: April 03, 2020, 03:38:36 pm »
Hi , I have a pot switch on my deluxe reverb  . when turned off it gives the amp more gain , would this mod work on a  vibro champ .
Its a 80s black  face
Thanks for any input
Fred

Offline shooter

  • Level 5
  • *******
  • Posts: 11015
  • Karma Loves haters
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #1 on: April 03, 2020, 04:05:23 pm »
Quote
when turned off it gives the amp more gain
from what I see on the schematic you should get the same "gain" with the pot on 0 and no switch.
Went Class C for efficiency

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #2 on: April 03, 2020, 06:07:33 pm »
Hi , I have a pot switch on my deluxe reverb  . when turned off it gives the amp more gain , would this mod work on a  vibro champ .
No. The deluxe reverb tremolo circuit is quite different than the VC circuit.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline fred

  • Level 1
  • *
  • Posts: 10
  • I love Tube amps
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #3 on: April 03, 2020, 06:19:13 pm »
Thanks for the fast answer back.

Offline shooter

  • Level 5
  • *******
  • Posts: 11015
  • Karma Loves haters
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #4 on: April 03, 2020, 06:37:14 pm »
Guess I missed something
"Switch on intensity pot"
does it short to ground the intensity pot, like if pot set to 0?  :dontknow:
Went Class C for efficiency

Offline fred

  • Level 1
  • *
  • Posts: 10
  • I love Tube amps
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #5 on: April 04, 2020, 10:47:36 pm »
Hi , my understanding is the intensity pot turns off all passing electric , gain and increases gain in the pre tubes .
Something about the regular stock pot takes away some gain from the preamp tube circuit even on 0 .
So on a deluxe reverb if you have a switched pot and it's turned off it adds gain .
I was lookin at the vibro champ wiring , it's not as complex as the deluxe is .
So thanks for the input ..

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #6 on: April 05, 2020, 06:25:02 am »
The 50K INT pot in the AB763 amps puts a heavy load on the signal path. When you disconnect the INT pot with the switch the signal increases because the 50K pot is no longer loading the signal. This results in the signal boost. Of course you no longer have tremolo. This is a popular mod for the AB763 amps.

The VC trem circuit is quite different and this switch mod will not work.
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: Vibro champ ? Switch on intensity pot
« Reply #7 on: April 05, 2020, 08:20:22 am »
Quote
puts a heavy load on the signal path
my missing link, thanks  :laugh:
Went Class C for efficiency

Offline fred

  • Level 1
  • *
  • Posts: 10
  • I love Tube amps
Hoffman Amps Forum image
Re: Vibro champ ? Switch on intensity pot
« Reply #8 on: April 05, 2020, 09:44:34 pm »
Thanks sluckey you explained it well .
It is a great mod on the deluxe reverb . I also have the NFB control , called soul control . and if you pull v1 it adds more gain too .
Amps are amazing .
Sluckey , I have that 1940 National amp all up and working great . the field coil does sound nice . I did the rat nest wiring .
It's not pretty , but looks like the 1940s  . thanks again

 


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


password