Analog Signal Generator

This is my scruffy old analog signal generator that I picked up for $15 or $20.   I was actually surprised it still worked, given the apparent age.

If you don't have a signal generator and you see one going cheap, I'd suggest buying it if you are going to be building a few FX pedals or playing with amps.  While it doesn't have all the bells and whistles of the new digital ones, it just sits there and kicks out a nice sine or the occasional square wave - I never actually turn it off.

There's something to be said for having a reliable reference signal that never changes when fault-finding or testing pedals.  Given that I'm a big fan of oscilloscopes for testing pedals, it goes without saying that a good signal generator is a must-have (at least for me, anyway).

For pedals, I always run it at 440hz, and 130mv TRMS.  While 1kHz is usually considered a standard test wave, it annoys me after a while.  As you probably realise, 440hz is actually the A string of a guitar.  

I use sine waves for testing most things, except for filters or equalisation that actually need harmonic content to filter, which is where I use a square wave.  

Sine waves are great for testing any kind of overdrive/fuzz/distortion, as you can actually see the harmonics generated by distorting the wave, as sine waves have no harmonics by definition, just the fundamental frequency.

These can also be used to test output transformers on amps, but that's a topic for another post.