Low voltage of 32 volts and below keeps the sound clean and anti-sluggish 

Low voltage 32 volts and below, steady sound, clean, anti-sluggish
10k bias resistor replaced 2k2
27k resistor 2 pieces replaced by 10k 2 Watt Milar input replaced by 104/100n need to add ceramic 104 in the 10 OMh resistor series to dampen stray frequencies okay I hope this video can be useful thanks
Low voltage 32 volts and below, steady sound, clean, anti-sluggish
Modif socl 504 Low voltage
Socl 504 modification, solid bass