YAMAHA CA-800II

Commentary

A pre-main amplifier equipped with a main amplifier section for switching between class B and class A operation, continuous loudness, and tone jump.

The main amplifier uses a pure complimentary service OCL circuit for all stages. Moreover, since the bootstrap circuit is eliminated, there is no phase disturbance and excellent transient characteristics are shown.
By switching the switch, high-power class B operation and class A operation without crossover distortion and notch distortion which affect sound quality can be selected.

A large power transformer and 10,000 μ Fx2 filter capacitor are used for the power supply.
In addition, stability is improved by using a separately set constant voltage power supply that drives all stages except the power stage.

Equipped with two protection circuits, power transistor protection and speaker protection.
The power transistor protection circuit employs a limiter system that detects when the ASO is exceeded and limits the input. Even when the protection circuit is activated due to overload or other reasons, the output only decreases and playback is not interrupted.
The speaker protection circuit uses a circuit method unique to Yamaha. When the DC voltage at the output terminal exceeds ± 2 V, a relay operates to cut off the signal path to the speakers. This circuit automatically returns when the DC voltage falls below ± 2 V. It also functions as a power muting, preventing shock noise when the power switch is turned on.

The equalizer amplifier section obtains a large gain while maintaining a low distortion rate and high stability by means of an NFB 4-stage direct-coupled circuit using a low-noise transistor, a high power supply of + 50 v constant voltage, an emitter-follower type output stage capable of reducing output impedance, and a sufficient amount of NF.
The EQ element combines a evaporated metal film resistor (error ± 1%) and a styrofoam capacitor (error ± 1%, ± 2%). In addition, tantalum capacitors with little leakage current and aging are used in various parts to achieve high precision characteristics.
In addition, the Phono1 circuit is equipped with an impedance change-over switch, which can be changed in three stages according to the load impedance of the cartridge.

The tone control circuit is an NF type with a phase inversion type 6-stone amplifier.
Both Bass and Treble have two levels of turn-over frequency, and the circuit operates as a flat amplifier when set to the Tone Defeat position.

The filter circuit consists of a phase-inverted 3-element amplifier. The low filter has three selectable positions : 70Hz/off/20Hz, and the high filter has three selectable positions : 6kHz/off/12kHz.

The audio muting switch has a tone jump position that bypasses the tone amplifier and filter amplifier.

Equipped with audio muting that can reduce the gain by 20 dB.

It is equipped with continuous loudness. In this circuit, a volume dedicated to loudness is provided so that compensation can be made based on the efficiency of the listener's ears and speakers, the size of the room, and the volume of the volume.

Equipped with two tape circuits.

The preamp and main amplifier can be used separately.

Equipped with two types of speaker terminals.

It is equipped with 4 AC outlets.

The front panel is made of silver hairline finish, and the cabinet is made of Castor open pore finish.

Model Rating

Type	Pre-main amplifier
Main Amplifier Section
Circuit system	Class B / Class A operation switching type Pure complimentary service SEPPPOCL circuit directly connected to all stages
Dynamic Power (IHF)	Class B operation : 160W (8 Ω)
Effective power	When both channels are operating 20 Hz to 20 kHz : 10W + 10W (8 Ω, Class A operation) 60W + 60W (4 Ω, Class B operation) 50W + 50W (8 Ω, Class B operation) 1kHz: 10W + 10W (8 Ω, Class A operation) 70W + 70W (4 Ω, Class B operation) 55W + 55W (8 Ω, Class B operation) Single-channel operation 1 kHz : 10W/10W (8 Ω, Class A operation) 90W/90W (4 Ω, Class B Operation) 60W/60W (8 Ω, Class B operation)
Total harmonic distortion factor	Class A operation : 0.1% or Less (Effective Output) 0.02% or Less (at 1W output) Class B operation : 0.1% or Less (Effective Output) 0.04% or Less (at 1W output)
Cross modulation distortion factor (70Hz:7kHz=4:1)	Class A operation : 0.1% or Less (Effective Output) 0.05% or Less (at 1W Output) Class B operation : 0.1% or Less (Effective Output) 0.05% or Less (at 1W Output)
Power bandwidth (IHF, both channel drive)	Class A operation : 5 Hz to 100 kHz Class B operation : 5 Hz to 70 kHz
Frequency characteristic	10 Hz to 100 kHz + 0 -1dB
Input Sensitivity / Impedance	Class A operation : 345mV/100k Ω Class B operation : 775mV/100k Ω
Output terminal	Speaker jacks : 2 channels Headphone terminal : 4 Ω ~ 16 Ω
Damping factor	70 (1 kHz, 8 Ω)
Signal-to-noise ratio (IHF, A-network)	100dB
Residual noise	0.8 mv (Pre + main amplifier, 8 Ω)
Preamplifier Section
Circuit system	Equalizer amplifier, microphone amplifier : 4-stage direct connection NFB-type amplifier Tone Control Amplifier : 6-Stone Amplifier
Input Sensitivity / Impedance	Phono1 : 3mV/30k Ω, 50k Ω, 100k Ω Phono2 : 3mV/50k Ω Mic : 2.5mV/100k Ω Tuner, Aux1/2, Tape PB A/B : 120mV/50k Ω
Output Level / Impedance	Tape rec outA/B : 120mV/2k Ω Pre out : 775mV/2k Ω
Phono maximum allowable input	310 mVrms (870mVp-p, 1 kHz, 0.1% distortion)
Harmonic distortion factor (Pre out 20 Hz to 20 kHz at rated output)	Phono1/2 : 0.1% or less Tuner, Aux1/2, Tape : 0.02% or less
Frequency characteristic	Phono (RIAA deviation) : 30 Hz to 15 kHz ± 0.2 dB Tuner, Aux1/2, Tape PB : 10 Hz to 50 kHz + 0.5 -1dB
Signal-to-noise ratio (IHF, closed circuit A network)	Phono1/2:80dB Mic:70dB Tuner, Aux1/2, Tape : 90 dB
Tone control	Bass : ± 15 dB (50 Hz), Turnover Frequency : 250 Hz, 500 Hz Treble : ± 10 dB (10 kHz), Turnover Frequency : 2.5 kHz, 5 kHz
Filter	Low : 20Hz/70Hz, 12dB/oct. High : 6kHz/12kHz, 6dB/oct.
Loudness control	Continuous loudness corresponding to an equal loudness curve
Audio Muting	-20dB
<General>
Accessory circuit	Transistor protection circuit (ASO detection limiter system) Speaker protection circuit (voltage detection relay drive system) Operation switch (class A / class B operation changeover switch) Tape dubbing switch Continuous loudness Tone jump
Semiconductor used	Transistor : 61 Zener diode : 6 pcs Diode : 30 pcs
AC outlet	Power switch interlock : 2 systems, max200W Power switch not interlocked : 2 systems, max200W
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	140W (rating, Electrical Appliance and Material Control Law)
External dimensions	Width 436x Height 144x Depth 323 mm
Weight	14.0kg