I have a device designed that allows you to set amp gains up to clipping as well as find headunit (RCA) clipping volume, and I was wonder what kind of interest people might have in it. The circuit allows you to visually watch the waveform your amp or headunit/RCA source is producing with a laptop/computer using free software. (Audacity) The device is connected to a microphone input of a computer and to the amp or headunit, and you crank up the gain or volume while playing a test track until you see the wave deforming (clipping) and then back it off. The device is relatively cheap compared to a DD-1 or oscilloscope, and though testing has been limited (I only have one bass amp and headunit), it has worked perfectly. If you are interested in the device or have questions, please respond.
P.S. I plan to work on making the device compatible with Android phones/tablets headphone jack (if it isn't already), and there are apps that display the waveform.
Here is a picture of a prototype