YAMAHA CA-400

Commentary

A pre-main amplifier with improved characteristics by adopting a monolithic IC for the equalizer amplifier.

All stages are directly connected to the pure complimentary service OCL circuit in the main amplifier section. The original circuit that takes out the differential amplifier output by push-pull and drives the driver stage of class A operation with constant current further reduces distortion. Moreover, since the bootstrap circuit is eliminated, there is no phase disturbance and excellent transient response characteristics are obtained.
In addition, the supply voltage to the driver stage is set higher than that of the Darlington-connected power transistor, and low distortion rate regeneration is realized even under 4 Ω load.
By performing temperature compensation and voltage compensation using a transistor, fluctuation of the AND current is suppressed, and crossover distortion and switching distortion are improved. In addition, in OCL amplifiers that amplify linearly to low frequencies, the speakers may generate unnecessary vibrations in ultra-low frequencies. Therefore, the first stage differential amplifier is used as a subsonic filter, and the speakers are protected by cutting the frequencies below 12 Hz with a slope of 12dB/oct.
In addition, Yamaha's original protective circuit is mounted so that the speaker protective circuit operates when an abnormal DC voltage is generated at the output terminal due to some trouble.

The equalizer amplifier uses a 3-stage direct-coupled monolithic IC of an intermediate emitter-follower type.
In this circuit, the gain of the first stage is large and the circuit is driven at a constant voltage of + 30 v, so that the dynamic margin is sufficient.
In addition, in order to prevent the degradation of the high-frequency characteristics due to the stray capacitance of the shield wire, the Function switch and Tape switch are mounted on the equalizer board like the CA-1000II, and are connected directly to the rear panel with connectors.

The tone control circuit uses an E-E feedback NF type with a 3-stage direct-coupled amplifier. It has good control characteristics and residual noise of 0.4 mV. It also has a Tone Defeat switch that provides flat frequency characteristics.

With a built-in microphone mixing circuit, mixing recording is possible from the Tape Rec Out jack.
When the Tape switch is set to the Mic Rec position, a mixed signal of the source and microphone is output to the Rec Out jack.

The power supply uses a large power transformer with good regulation and a 4700 μ Fx2 large-capacity capacitor.
In addition, all stages except the main amplifier are driven by a constant voltage power supply, providing a stable voltage supply.

Features include a tape-dubbing switch, low / high filter, two speaker outputs, and three AC outlets.

It is designed to reduce shock noise when the power switch is turned ON/OFF and click noise when switching various switches.

The cabinet has a castor finish.

Model Rating

Type	Pre-main amplifier
Main Amplifier Section
Dynamic Power (IHF, 1 kHz)	90W (4 Ω) 70W (8 Ω)
Effective power	20 Hz to 20 kHz (both channel drive) : 25W + 25W (4 Ω) 20W + 20W (8 Ω) 1kHz (both channel drive) : 28W + 28W (4 Ω) 22W + 22W (8 Ω) (single-ch drive) : 35W/35W (4 Ω) 27W/27W (8 Ω)
Total Harmonic Distortion Factor (AUX In)	0.1% or Less (Effective Output) 0.04% or Less (at 1W output)
Cross modulation distortion factor (at effective output)	Not more than 0.1%
Power Bandwidth (IHF, 0.5% distortion factor)	8 Hz to 70 kHz
Load impedance	4 Ω ~ 16 Ω
Damping factor (1 kHz, 8 Ω)	50 or more
Channel separation	50 dB or More (1 kHz, Effective Output)
Residual noise	0.4 mV or less
Preamplifier Section
Input Sensitivity / Impedance (1 kHz, effective output)	Phono1, 2 : 3mV/47k Ω Mic : 3mV/40k Ω AUX1, 2, Tuner : 150mV/55k Ω Tape PB A, B : 150mV/55k Ω
Phono maximum allowable input (0.1% distortion factor)	135mVrms
Mic maximum allowable input (distortion rate 0.3%)	400mVrms
Output Level / Impedance (1 kHz)	Tape Rec Out A, B : 150mV/1k Ω Pre Out : 450mV/2.7k Ω Mic Rec Out : 450mV/2.7k Ω DIN (Tape Rec Out A, B) : 30mV/80k Ω DIN (Mic Rec Out) : 95mV/80k Ω
Total harmonic distortion factor (Pre-out at effective output)	Phono1, 2 : 0.1% or less
Frequency characteristic	Phono (RIAA deviation) : 30 Hz to 15 kHz ± 0.5 dB Mic → SP Out : 100 Hz ~ 10 kHz + 0. 5-6 dB AUX → SP Out : 20 Hz ~ 50 kHz + 0.5 -1dB
S/N (IHF, A Network)	Phono → SP Out : 75 dB or more MIC → SP Out : 70 dB or more AUX → SP Out : 90 dB or more
Tone control	Bass : 50 Hz, ± 12 dB Treble : 10 kHz, ± 10 dB
Filter	Low:50Hz(12dB/oct) High:8kHz(6dB/oct)
Loudness	100Hz:+8dB 10kHz:+5dB
<General>
Semiconductor used	Transistor : 31 IC : 2 Diode : 9 pcs Zener diode : 1 unit
Power consumption (Electrical Appliance and Material Control Law)	70W
AC outlet	Power switch interlock : 1 system, maximum 200W Power switch not linked : 2 systems, maximum 200W
External dimensions	Width 436x Height 144x Depth 300 mm
Weight	8.0kg