A true rarity and a lavish example of structured design, too.
The A-X9 is a sibling of the very successful P-L10, M-L10 and M-7050 and in fact came first in the lineup - so no Gm processors yet (as such), Super-A not yet in handy modules and no feather-touch buttons either !
At 158,000¥, the A-X9 wasn't exactly high-end by japanese standards but nevertheless packed with goodies only the vanishing 1970s could provide at such price points.
Super-A, of course, Class-A DC-Servo phono stage and simplified two-stage structure without flat amp.
Super-A works with an Active Bias Circuit, strapped across the input of the power stage : this ABC controls the amount of bias following the output level's variation.
By feeding them sinusoidally-varying reverse bias during their half-cycles of non-conductivity, output transistors never switch off. No switching distortion as in normal Class B, no useless heat production as in Class A.
As idling current is to be set at 50mV for each channel, Super A, if not regular Class A, produces a fair amount of heat just the same.
The two-stage structure is like that of the slighty later Luxman amplifiers : no flat amp and tone controls wrapped around an NFb loop at the output stage.
The Class-A DC-Servo phono section serves equally for MC and MM cartridges, applying a 60dB gain for the former and 38dB for the latter ; both phono inputs can receive either type of cartridge, with a 3-step choice of input impedance.
A big 380VA toroidal transformer with windings for each stage to be fed, four pairs of Fujitsu RET (2SC2525 / 2SA1075, 120W Pc, 80MHz fT, 12A Ic) power transistors and a bank of eight 4700µF / 71V caps placed horizontally under the toroidal power transformer.
Also four special EL FETs for the phono EQ (really : two matched Toshiba 2SK146 in one box), two output relays, copper bus bars and a bombastic chassis.
The volume pot is the ALPS RK40 "black beauty", as used in almost all JP mid- and high-end between 1976 and 1984.
Build-quality-wise, this is all black glossy steel and aluminium. The front and top are made of a massive 4mm extruded aluminium piece ; the articulated bottom lid is equivalent.
The "display" is made of a semi-reflective metallic strip which hides the unselected functions but lets the lit selected ones pass through - strikingly elegant, very effective and carried on to the later P-L10 bestseller.
Of course, nothing is ever perfect, this mainly works at night for during the day the non-selected functions pass through the strip in black as you can see here :)
The slightly frosted aluminium, shiny vertical selectors and mirror strip make for a finely detailed, well-proportioned and near-Sony finish quality.
Only the well-matched but fairly banal casing and the push-buttons are a bit of a let-down but so what ? The sensual feel of the big volume control makes up for those. And the sound, of course.
I must admit I bought my A-X9 mainly for its design, never having seen one then, let alone more recently. But the A-X9 is not only very well designed, it also is a very hot and able music maker : strain-free, stable stereo image at all levels, lots of power and not a trace of distortion in sight.
The A-X9 didn't sell too well to say the least but its evolution made the P-L10 and M-L10 : both true bestsellers.