Welcome To the Hoffman Amplifiers Forum

September 06, 2025, 09:51:47 am
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Hmm, does red plating make a sound to reveal itself?  (Read 2127 times)

0 Members and 1 Guest are viewing this topic.

Offline RoadShow

  • Level 2
  • **
  • Posts: 105
  • Disturbing the Peace Since 1955
Hoffman Amps Forum image
Hmm, does red plating make a sound to reveal itself?
« on: October 21, 2024, 09:50:19 am »
I understand what red plating is and what causes it, but I've never actually experienced it.

I see people mention that they had a tube red plate, but is there something that made them look to see it?

I suspect that the amp doesn't sound right when it occurs, so what is the change in the sound?

Or, should I be looking in the back of the amp whenever I use it... just in case.

Thanks...

Offline pdf64

  • Level 4
  • *****
  • Posts: 2965
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #1 on: October 21, 2024, 09:58:09 am »
By definition, a redplating valve draws a lot of idle current.
That imbalances a push pull stage / typically increases HT ripple, to such a degree that the amp hums at twice mains frequency.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him! BBC News feature  https://www.bbc.co.uk/news/articles/cm26llp

Offline Merlin

  • Level 3
  • ***
  • Posts: 549
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #2 on: October 21, 2024, 10:00:51 am »
Redplating can be due to hot bias in which case you won't necessarily hear anything unusual. Or it may be a symptom of a significant fault that is audible. So both options are possible!

Offline tubeswell

  • Level 4
  • *****
  • Posts: 4201
  • He who dies with the most tubes... wins
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #3 on: October 22, 2024, 08:26:35 am »
If you happen to be playing some power chords, the amp can sound incredible as it’s red plating, and then it dawns on you what might be happening, but by then it’s too late…
A bus stops at a bus station. A train stops at a train station. On my desk, I have a work station.

Offline stratomaster

  • Level 3
  • ***
  • Posts: 585
  • Don't guess, measure.
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #4 on: October 22, 2024, 09:36:40 am »
In my experience, the worst cases both look and sound like Darth Vader waiting in the dark to strike your amp down.

Offline acheld

  • Level 3
  • ***
  • Posts: 1263
  • No well conceived plan survives the event.
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #5 on: October 22, 2024, 09:54:20 am »
The good news is that neither Darth Vader or red plating are subtle.   

At least, not subtle once you have experienced it.   When I hear that increasing 120Hz hum, I know what switch to reach for!

Offline shooter

  • Level 5
  • *******
  • Posts: 11012
  • Karma Loves haters
Hoffman Amps Forum image
Re: Hmm, does red plating make a sound to reveal itself?
« Reply #6 on: October 22, 2024, 10:12:44 am »
was at a local outdoor jam weekend, one of my amps was "on display" for the various guitarist to try out.  That night the "headliner band" jammed out, during a break I was backstage, told the lead guitarist "Your twin sounds like the PA tubes are on their last legs"
He smiled, said; "It's amazing the sound I get, I have my tech ONLY install tubes that are ready to die, I get one or two shows on each set" 
Went Class C for efficiency

 


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