I already say this before but this particular rectifier fizz come from transformer imo (Schumacher transformer or holy grail 2 channel (mean "revC/D/E/F and in sometimes rev G like your ex) component). I'm sure it's why 3 channels rectifier/roadster/roadking or "standard rev G" haven't this fizz...
Btw it's would be interesting to put this transformer into a roadster for verifying this theory