Yamaha C-2a

October   1 9 7 8 october 1978
1 9 8 3 1983

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.

Yamaha C-2a, image 1 Yamaha C-2a, image 2 Yamaha C-2a, image 3
Yamaha C-2a specifications
Title Value
Inputs : 2,5mV / 100 Ohm / 47kOhm / 68kOhm / 100kOhm (phono 1 MM)
100µV / 50 Ohm (phono 1 MC)
2,5mV / 47kOhm (phono 2 MM)
150mV / 47kOhm (Aux / tuner / tape 1 & 2)
Max. input : 350mV (MM / 1Khz / 0,01% THD)
10mV (MC / 20Khz / 0,03% THD)
1V (lines / 20Hz...20Khz / 0,01% THD)
Outputs : 2,0V / 250 Ohm (PRE out 1 & 2)
150mV / 100 Ohm (REC out 1 & 2)
Max. output : 15V (PRE out / 0,01% THD)
18V (REC out / 0,01% THD)
THD : < 0,003% (10V output ; phono MM to REC out)
< 0,01% (1V output ; phono MC to REC out)
< 0,003% (10V output ; lines to PRE out)
THDR (HP-IB audio Analyzer) : < 0,0007% (phono MM to REC out ; 1V output ; 20Hz...20Khz)
< 0,0007% (lines to PRE out ; 2V output ; 20Hz...20Khz)
RIAA accuracy : ± 0,2dB (phono MM ; 20Hz...20Khz)
± 0,3dB (phono MC ; 20Hz...20Khz)
Frequency response : 10Hz...100Khz (lines ; ± 0,2dB)
S/N ratio : > 92dB (MM ; IHF-A)
> 78dB (MC ; IHF-A)
> 105dB (lines ; IHF-A)
Residual noise : < 0,03µV (vol. min.)
Channel separation : 90dB (phono MM to PRE out ; vol. max. ; 1Khz ; 0 Ohm shorted)
60dB (phono MC to PRE out ; vol. max. ; 1Khz ; 0 Ohm shorted)
90dB (lines to PRE out ; vol. max. ; 1Khz ; 1kOhm shorted)
Bass control : ± 10dB at 20Hz (turnover 350Hz)
Treble control : ± 10dB at 50Khz (turnover 3,5Khz)
Subsonic filter : 15Hz (12dB/octave)
Audio muting : -20dB
PC : 36W
Dimensions : 43,5 x 7,2 x 32cm
Weight : 7,9kg.
Supplied phono load plugs : 100P (Japan-only)
150P (Japan-only)
220P
330P
470P
List price : 170,000¥ (1978...1983)
Yamaha C-2a : 0 topic
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page online since : april 2009
page updated : january 2011
page type : LGT / KNB
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