Harmonics control may I say?
if you are talking about power tubes I highly discourage overbiasing to warm up
the sound. It just gives you supernova and runaway tubes easily.
Gain and driver tubes are a different story. You can get pretty good returns from say biasing a 6SN7 from say 2mA to 4mA depending on B+ and plate resistor. However since a lot of modern designs are direct coupled. Increasing bias at gain stage by tweaking grid voltage or cathode resistor usually means decreasing bias at driver stage. Not for the faint of heart.
if you are talking about power tubes I highly discourage overbiasing to warm up
the sound. It just gives you supernova and runaway tubes easily.
Gain and driver tubes are a different story. You can get pretty good returns from say biasing a 6SN7 from say 2mA to 4mA depending on B+ and plate resistor. However since a lot of modern designs are direct coupled. Increasing bias at gain stage by tweaking grid voltage or cathode resistor usually means decreasing bias at driver stage. Not for the faint of heart.