Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I have been looking at these for possibly making a dummy load(s)

I'm noticing that they are available in a variety of resistance ratings as well as watts.

I've googled it quite a bit but noticing what seems to be some really extremely skewed items just wondering what some of the applications are for example a 100 watt 0.025 ohm resistor  :loco

Obviously Dale Vishay...Ohmite don't just make these for people testing amps  :lmao:

Also sorry I have to ask I may try it what happens if you connect an amp to for example a 3.9 Kohm resistor?!  :grr  xP

Anyhow I may not buy some of these I dont see many exactly 8 ohm specimens obviously I can work around that.

But it may be something that you guys that have fixed two million amps have used maybe twice idk  :tu:

You can get an 8 ohm 100W resistor to test an amp but a better option is to make an attenuator with inductors and resistors that better simulate a speaker load, I think over in the Marshallforum they came up with a really good homemade version that they use so they can run the tube amps at full power and still tap off at a lot lower power output. A Marshall 800 amp sounds fantastic when you crank it.
https://marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

Other uses could be anything from radio transmission, speaker crossovers, industrial applications like DC motor braking, speed regulation of wiper motors in your old car etc.
Cheers
Mick

Yes sir thanks  :dbtu:

Thank you for making a note that we need to be dealing with impedance here so maybe I can get a calculator out and try to design something that would result in 8 ohms reactance at test frequency and be about 100? watts  xP

The reactance thing is more for playing, it sounds and feels more like a real speaker.
Load resistors are for testing power output.  You don't want to listen to a test tone at 100 watts.   :)  For PA type stuff, you might need to test 1000 watts or more.
Fortunately, the impedance of a resistor is usually very close to it's resistance value, so there are no issues with the measurements.
Some power resistors require heatsinking, and some don't.  A fan may also be required, but it depends on what kind of power levels you are testing.
A small difference in the resistor (ex. 7 ohms instead of 8) is workable and the calculations will account for it.
Solid state amps can usually be run into high resistance (your 3K9 example) but you won't be able to do any power testing.
Tube amps are picky about being run into the correct impedance.

Yes sir thanks you covered a lot of ground there  :dbtu:

Back when I used to send lots of money 🤑💰 to Summit and Jegs there was a particular automotive machine shop where I used to spend lots of money  xP

They are still around in fact last time I visited but anyhow they have a dyno.  I had never seen it in action until one day I was dropping off or picking up etc they were doing some testing in the dyno room and I was privileged to watch for a moment or two.
I can tell you it was truly awesome and amazing to see the engine spin up seemingly trying to break free of the pedestal stand and see the guys at the desk controls it is very cool  :dbtu: And LOUD  :dbtu:

Of course I had read about all this stuff and noticed when I was actually witnessing it live that when they tested at rpm they only very briefly sustained that rpm perhaps long enough to get readings then they decreased the throttle back to idle  :grr

That was stark contrast to what I had envisioned such as "alright Fred take er up to 6500 let er rip"  8|

Side note yes they did have an incident where something came loose and fortunately damaged or went through a wall and nobody got hurt.

Anyhow you're wondering what does this have to do with anything well here ya go  :lmao:
I was reading a manual for a tone burst generator  :tu:


IMG_20260109_232220480 (1).jpg

So maybe I can try to figure out how to use my tone burst generator  :dbtu: to test amplifier output.

Idk how I'm gonna measure 5% distortion but I guess I can eyeball when the signal starts to get crappy  :-X