Follower of the CA-1000 bestselling series - a bit cheaper and not fully in Class A anymore.
"Dual Class A amp with ZDR" means two amplifier sections (one in A, the other in AB) "circling" the loudspeaker terminals with an NFB loop to effectively damp the counter-reaction between amplifier output and bass cones - the schematic is below.
Two 47,000µF rectifying caps, two 22,000µF smoothing caps and a basic structure which is quite reminiscent of the old CA-1010.
Also present is a pre/main set of i/o terminals and big speaker terminals.
Besides ZDR (Zero Distortion Rule : watch distortion at the output and inject a reversed-phase equivalent at input), a nice touch was added : RICHNESS !
Richness isn't an elusive tonal quality but a three-position tone control to perfectly match the A-1000 to Yamaha's bestselling NS-1000 series and later two siblings.
• Position 1
fits the NS-2000 by adding 7,5dB at 30Hz
• Position 2
belongs to the NS-1000M and NS-1000x by adding 7,5dB at 40Hz
• Position 3
is a freebie adding the same amount of dBs but higher at 50Hz.
The export A-1000 was fairly different and named A-950 in Japan.