Completely rebuilt headamp with the 4 low level audio tubes filaments converted to a regulated, soft start, dc supply for low noise performance and long life. Noise is 20db lower, due to the regulated filament voltage, over the stock configuration. Rently I bypassed the negative bias supply diodes and removed most of the noise spikes, which manifest in the audio as buzz. Filament voltage starts out at 2 volts and ramps up to 6.3 volts DC over 15 seconds of time. Regulator circuit is on its own custom made circuit board , not point to point hand wired. .All power supply and coupling caps replaced with new high performance caps. 6L6’s screen grid resistors replaced with 1% ,7 watt metal film resistors. Power supply rectifiers replaced with fast transition Schottky diodes. Before and after noise graphs are shown. All 6 output tubes replaced with brand new Mesa Boogie 6L6 str428. Output power at 1khz is 200 watts @ less than 2% thd.