WIKI – Total Harmonic Distortion / THD
ap.com – THD+N

tungsol.com – Why is there a difference in Tube and Transistor sound

In the heyday of tubes and transformers, a certain amount of distortion may of been desirable but certainly not in the modern day of digital mixing consoles and digital signal processors. Unlike analog tape and analog circuits, most digital audio is a stream of 0s and 1s (binary). There is nothing to be gained by clipping one or more of these devices in a signal chain but ugliness.

Case in point. Recently while performing some electronic measurements on a Soundcraft Vi6, I tested the threshold of clipping going in and out of the console to learned whether or not the red light on the input / outputs comes on at the same time or not.