Testing an Amp for Harp

When you play a 3 and 4 draw together, a third note appears that sounds two octave lower than your 2 draw pitch. This is called a Difference Tone and is what we listen for when testing harmonica amps (a G Harmonica is a great harp to use for this test). Simply stated, a good amp is one where you can here the difference tone well and it fills the room with bass (warm and resonant bass) and a bad one is where you can't hear it (thin tone) well.