[LarryFS]

I have a 38-3 which has the same four point tone control as the 38-4 and 38-5 according to the 1938 Philco sales catalog (see http://philcoradio.com/phorum/showthread.php?tid=15785).  Position 2 of the switch is "brilliant" for speech; position 3 is "bright" for normal reception of music; position 4 is "mellow" for the first noise-reducing stage; position 5 is "deep" for noise-reducing for distant reception.  I hear very little difference between positions 2 and 3 on mine.  I can't comment on how each of the 4 tone circuits functions based on the schematic.

Larry