How to Test a Harp Amp - The Differential Tone

Did you know that when you play a 3 draw and 4 draw at the same time 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 up the room with bass (warm and resonant bass response) and a bad one is where you can't hear it (thin tone) well (or in some cases at all).

To hear more information on this subject and watch "How differential and overtones work" on Steve Baker's Interview and Contributor Ryan Walker's "Lesson 3 - Cupping and Control of Tone"