Last ultra 2-channel from Pioneer - a mini-Exclusive of sorts.
Really an Exclusive but Pioneer seemingly prefered to hook the A-09 with the PD-T09 (aka PD-95) and other high-end components which, however did not bear the "09" tag : D-07 DAT, T-1100S recorder and S-HE100 loudspeaker !
That would've been the role of the A-07 but it doesn't fit either - not only Sony makes strange moves :)
Anyway -
Borrowed from the earlier Exclusive M7 is the separation of... everything : two boxes in one, voltage and current stages remain fed by different transformer windings.
The transformer is a copper-shielded 400VA EI which feeds the control, phono, voltage and current sections separately.
The attenuator is real luxury : hand-made, it isn't a regular potentiometer but a 40-steps calibrated resistance array allowing a maximum of 0,5dB balance error. As in the Exclusive C7 and in fact, it is the same as in the C7 but there is only one for both channels ; the same attenuator was used in the Micro Seiki CL-M2DC ultra preamp ; it was actually built by Tokyo KO-ON Denpa under the Type C-3 reference.
Stereo separation up to 20Khz shoots high at 90dB.
The output transistors are bipolars from Toshiba (2SA 1265 and 2SC 3182) ; drivers also bipolars (2SC 4793 and 2SA 1837). The low-NFB, DC-Servo and current-mirror input stages start with two FETs.
Output stages have no NFB loop at all - a late return to the 1979 M-Z1a ?
The capacitor block holds two 15,000uF and two 30,000uF, all Pioneer-made. The preamp stages hold 22 bipolars and FETs (per channel) ; regulations everywhere.
Low internal impedance, non-magnetic almunium slabs, diecast and higly ribbed resin base, select custom caps, non-symmetrical and ribbed heatsinks, ultra-short signal paths (the power transistors are all set at the back of the heatsinks, too), realy-driven i/o and protection, an OFC AC cord which enters the enclosure by the underside to reach the transformer directly, and fully dual-mono structure (after the transformer) - all this copper-plated from top to bottom.
The A-09 is a full Class A design with low distortion, very high damping factor and no NFB loop in the final stage : up to 2x 140W on a 2 Ohm load !
Albeit fairly rare (it did cost 480,000¥), the A-09 is one of the best and most "musical" integrated amplifiers ever made.