Yamaha C-2a

Updated version of the original C-2 bestseller and itself a bestseller.
Update isn't really accurate for if the exterior is nearly identical, the inside is quite different !


The phono EQ is made of Yamaha's own 2SK-101 Dual-FET used as differential input amplifier of a low-noise high-gain Dual FET, with a cascode bootstrap circuit and automatically balanced active loading, followed by a current-mirror push-pull pre-driver, and a two-stage emitter-follower complementary push-pull SEPP output amp.

High-precision high-capacity metal film resistors and newly-developed polypropylene film capacitors with temperature-compensating capabilities make the parts beyond the 2SK-101 Dual-FET.
The latter also are the center of the Current Noise Reduction Circuit : a phase-reversed RIAA stage clamping the actual EQ stage to lower distortion and noise.

The tone control stage is similar to that of the EQ stage, allowing output impedance to remain low at 250 Ohm.

The 4-gang volume control is made of a conductive plastic material, with two gangs acting before the flat amp and two after ; these were home-made, or so said Yamaha.
Two more gangs are present for the coaxial balance control.

Power-supply was not neglected : "low-distortion, low-noise, high-speed constant-voltage circuit made of a low-drift comparator using a dual transistor, with a cascode bootstrapped active load, followed by a low-noise avalanche effect diode for generating the reference voltage".
The MC stage has its own regulated power supply derived from the main one.

Five capacitance load plugs with a dedicated back terminal replaced the phono 3 input of the original C--2, allowing to tweak high frequency response.


The 2a "update" came in when Yamaha launched several complementary units which others had in their lineups since the 1960s (HA-5, HA-3, HA-1 separate head-amps and EC-1 3-way crossover) but, unlike the C-2a, none of these sold in significant quantities - Sony, Denon and to a lesser extent Pioneer had already cornered that part of the market.

The power amp going with the C-2a was at first the B-2 V-FET masterpiece until 1979/80, then the not-as-lush M-2 powerhouse (B-5 in Japan) - all bestsellers !

The C-2a didn't see a silver version like the C-2 did (somewhat) but was updated in 1983 as C-2x - again quite different inside but this time very rare.


Restoration nudies aplenty at the indispensable amp8.com : page 1 and page 2 and page 3.