Last high-end 2-channel audio development of Onkyo, launched at the same time as the Japan-only and diminutive A-1E.
The P-388 and M-588 were however also exported outside Japan and, depending on country, available until the very late 1990's.
The P-388 embodies the refinement of what was put inside the P-308 (1986) but gone were the In-Phase transformers, and most of everything else, including the myriad of switching functions.
In are two AEI "laser" transformers, one for line sources and one for phono sources, plus another outside the enclosure for utilities such as relays or motor-driven source switching and volume control.
The power-supply section sees the back transformer and two big caps delegated to feeding the L and R line sources ; the other four, two each, and the front transformer feed the MM and MC stages.
Unlike the latter, the phono MM and MC inputs each have their own terminals (and circuits) but no pF or Ohm switching...
Two balanced inputs are available (better than those in the Sony), along with three outputs - one normal and one phase inverted (both unbalanced) and a normal one in balanced format.
Two 6-step output attenuators are present with deported shafts, just like the REC Out selector. Very select component entry, 70µ PCB tracks, dual-mono structure, Neutrik terminals etc.
The main circuit is organized as in the M-588 : double-differential input, double-Servo. And it is almost all made with discrete components : no ICs in the phono stages or anywhere else but in the stepped outputs.
The P-388F is an excellent high-end preamplifier, better than the stock Sony TA-E80ES!