I've no clue about Mullard rectification but I have two assumptions that the second diode tube either rectifies a phase inversed signal or the split-phase signal(where one phase is lagging bihind another by 1/2period making a twice as freequet "lumps" that are much easier to smooth up with capacitors that have proper time delay. Inverting phases as well as splitting phases can be done using a transformer.
what does a Rectifier tube do?
I have an Air Tight Atm1 amp which uses 2 5ar4 Rectifier tubes. The manufacturer calls it Mullard Rectification. My question is what is Rectification? I ask becuase AirTight makes ATM3s which use the same tubes (EL34) but do not use 5ar4s for Rectification. Would that mean there is a different sound even though both amps use the same Output tube?