Tube Amp Bias - Default vs MinTHD and Bode plot on the Line 6 Spider Valve 112 (#003)

An experiment in biasing a tube amp.
Comparing 2 methods:
1. The recommended default bias of 35mV (=35mA)
2. Biasing for minimum % THD at 1kHz.

Additionally showing the amplitude vs frequency response of both methods.

Finally and audio comparison of the 2 bias methods.