Welcome To the Hoffman Amplifiers Forum

September 06, 2025, 12:39:08 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Signal strength for testing  (Read 2288 times)

0 Members and 1 Guest are viewing this topic.

Offline acheld

  • Level 3
  • ***
  • Posts: 1264
  • No well conceived plan survives the event.
Hoffman Amps Forum image
Signal strength for testing
« on: September 15, 2022, 02:40:52 pm »
I want to follow the signal through a preamp section with my 'scope, mostly to see for myself what happens to the signal after each triode. 

The question is:  what should be the signal strength I send?   I tried to measure the output of one of my guitars, but I'm questioning the results.

Using a Fluke 117 in AC V Max/Min function, six string strum is at about 80mV;  the A string comes in at about 30mV.  This is from a stock Ibanez single humbucker measured at the amp's input jack. Seems low to me, but . . .

What signal strength are you 'scoping with?   

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: Signal strength for testing
« Reply #1 on: September 15, 2022, 06:37:29 pm »
1KHz, 100mV, sine wave is easy to remember.
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: 11013
  • Karma Loves haters
Hoffman Amps Forum image
Re: Signal strength for testing
« Reply #2 on: September 16, 2022, 02:40:57 am »
^^^
I've found 800hz is more pleasing to my ears.
once i've run the test signal and recorded the stages, I typically leave the scope connected to the speaker, then slowly bring up the test signal til the scope display just starts to distort.
measure n note the signal amplitude as "max clean input"
that is the value I use for da math

Went Class C for efficiency

Offline acheld

  • Level 3
  • ***
  • Posts: 1264
  • No well conceived plan survives the event.
Hoffman Amps Forum image
Re: Signal strength for testing
« Reply #3 on: September 16, 2022, 10:15:17 am »
Many thanks!

Offline pdf64

  • Level 4
  • *****
  • Posts: 2965
Hoffman Amps Forum image
Re: Signal strength for testing
« Reply #4 on: September 16, 2022, 10:49:27 am »
FYI my Les Paul, which has vintage PAF type rather than hot pickups (Burstbuckers I think), puts out 2Vpk on initial pick attack.
If an input stage is underbiased, it’ll cause noticeable clipping there.
« Last Edit: September 16, 2022, 10:51:52 am by pdf64 »
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 acheld

  • Level 3
  • ***
  • Posts: 1264
  • No well conceived plan survives the event.
Hoffman Amps Forum image
Re: Signal strength for testing
« Reply #5 on: September 18, 2022, 09:53:59 am »
Quote
2Vpk on initial pick attack.

Whoa.  I think that would clip on any of my amps! 

 


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