From a time when early solid-state amplifiers in Class B ruled - Yamaha got back to basics with Class A.
The CA-1000 is the first of a very long line of very successful, very reliable and very heavy amplifiers which sold like hotcakes until the mid 1980s : japanese high-end-wise, the CA-1000 is the example everybody else quickly followed.
Two-sided circuit boards, low-noise MC preamp, variable loudness control, switchable Class A / Class AB modes are the rarities which very few other japanese makers had put in their top amplifiers in 1973.
The chassis construction and general layout also was to be a school case of how things would be done afterward : phono stage placed right after the terminals, as far away as possible from the power-supply section, huge 270VA transformer, bigga 18.000µF / 80V capacitors (two), 1% tolerance metal film and styrol resistors, 3-stage DC shelving tone controls, and fully differential with current-mirror power stage driver.
The Class A mode puts 2x 15W into 8 Ohm into your ears, and Class AB up to 2x 70W.
The "current steering" circuit allows the output pairs of transistors to remain in Class A for currents up to twice the bias current, with a power supply lowered to ±26V but a bias current increasing to... 0,5A !
In true Yamaha tradition, begun with the CA-1000, the phono stage is very rich with two inputs, one of which has a (back) selector for MC / MM 50KOhm / MM 100kOhm and a front selector for phono 1 / phono 2 and phono MC.
The phono 1 input has a semi-floating ground circuit attached to the back selector - better for MC cartridges ; phono 2 is fixed at 50kOhm and bypasses the additional preamp - better for MM.
The chassis itself is as sturdy as can be, with a difference in color for the wood enclosure : yellow-ish and very clear for the domestic models, warmer and darker for the export versions.
Depending if the recipient market saw the intermediary version (CA-1000 II), the CA-1000 remained available until the launch of the CA-1010 - aka CA-1000 III in Japan.
Like its CA-1000 II, CA-1010 and CA-2010 followers, the CA-1000 needs room to breathe as bias current is high and hot.
So was the sound quality and so were sales.
Nudies of a JP CA-1000 here.