YAMAHA A-3

Commentary

This pre-main amplifier was developed as the second DISC straight DC amplifier following A-1.

The EQ circuit consists of current mirror cascode bootstrap differential amplifier at the first stage, common-emitter amplifier at the second stage, and A-class pure complimentary service SEPP-OCL at the last stage.
The current mirror circuit provides sufficient gain, and the two transistors function as a push-pull circuit to cancel even order harmonic distortion. The cascode bootstrap circuit also reduces distortion factor degradation even if signal source impedance changes greatly depending on frequency when a MM cartridge is connected.
As for RIAA deviation, a high accuracy of ± 0.2 dB has been achieved by using a resistor with an error of 1% and a capacitor with an error of 2%.

The MC head amplifier has the same configuration as A-1 and uses a newly developed low-noise transistor.

It is equipped with a DISC switch. If you turn the switch ON, you can listen to the record through a very simple signal path of equalizer → DC high gain power amplifier.

Equipped with a phono selector that can switch the load resistance in 3 stages, it is compatible with various cartridges.
It is also equipped with a 100 Ω position for high output type MC type cartridge that does not require a head amplifier.

The power amplifier section is basically the same configuration as A-1. The first stage employs a low-noise Dual FET cascode bootstrap current mirror differential amplifier. The pre-drive stage consists of a Darlington connection and the output stage consists of a Darlington connection SEPP-OCL circuit. This DC power amplifier has an input sensitivity of 300 mV, which is approximately three times higher than that of an amplifier with a normal design. In addition, the drift of the midpoint voltage, which is a particular problem in DC amplifiers, is minimized by using a Dual FET that combines FETs with excellent electrical and thermal characteristics into one package.
The transistors used in each stage use elements with good linearity that have been carefully selected by hearing.

The tone control circuit uses a first stage differential to push-pull configuration IC. This circuit can be used when the DISC switch is OFF.
The A-3 tone control circuit uses Yamaha's original NF-CR type circuit. In addition, because of the self-defeat system, when in the center position, the element with a time constant deviates from the signal path and becomes flat accurately.
The turnover frequency can be switched between two levels for bass and treble.

Equipped with a subsonic filter.

The Rec out selector allows you to select the signal for Rec out regardless of the program being played by the amplifier.
In addition, two tape decks are possible, and mutual dubbing is also possible.

A large-capacity transformer and 10,000 μ Fx2 electrolytic capacitor are used for the power supply circuit.
In addition, to compensate for the limitations of electrolytic capacitors, metallized polyester film capacitors are connected in parallel to suppress the rise in power supply impedance.

Equipped with a Pc limiter and speaker protection circuit that detects the ASO area of the output transistor and protects the power transistor in case of overload or output short circuit.

It is equipped with a speaker switch to protect the speaker from noise when dropping the needle to the record.

Model Rating

Type	Pre-main amplifier
Effective power	55W + 55W (8 ohm, 20 hz to 20 khz, 0.05% distortion)
Total harmonic distortion rate (20 Hz to 20 kHz)	Phono1 MM-Rec out : not more than 0.005% (3 v) Phono 2MC-Rec out : 0.05% or less (1.5 V) Tuner-SP out : 0.02% or less (8 Ω, 27.5W)
Intermodulation distortion factor (60 hz : 7 khz = 4 : 1)	Tuner-SP out : 0.01% or less (8 Ω, 27.5W)
Power bandwidth	10 Hz ~ 40 kHz (8 Ω, 27.5W, 0.05% strain)
Damping factor	50 or More (8 Ω, 1 kHz)
Frequency characteristic	Phono-Rec out (RIAA deviation) : 20 Hz to 20 kHz ± 0.2 dB Aux, Tuner, Tape-SP out : 10 Hz to 100 kHz + 0 -2dB (8 Ω)
Input sensitivity	Phono1 MM:2.5mV(180pF) Phono2 MC : 60 μ V Aux, Tuner, Tape : 150 mv
Input impedance	Phono1 MM : 100 Ω, 47k Ω, 68k Ω, 100k Ω Phono2 MC : 10 Ω Aux, Tuner, Tape : 47k Ω
Maximum allowable input	Phono1 mm : 250 mV or more (1 kHz, distortion 0.01%) Phono2 mc : 5 mV (sensitivity 60 μ V, 1 kHz, distortion 0.05%)
Level at DISC ON	-6dB
Output Level / Impedance	Rec out : 150mV/600 Ω
Tone control characteristics	Turnover Frequency Bass : Treble: Maximum variable width Bass : Treble: 500 Hz, 125 Hz 2.5 kHz, 8 kHz ± 10 dB at 20 Hz ± 10 dB at 20 kHz
Subsonic filter	15 Hz, 12dB/oct.
Signal-to-noise ratio (IHF-A network)	Phono1 mm : 86 dB or more Phono2 mc : 70 dB or more Aux, Tuner, Tape : 104 dB or more
Residual noise level IHF-A Network	DISC on : 60 μ V or less DISC off : 130 μ V or less
NDCR (Phono1 MM-SP out, 1 kHz Strain 0.1%, Vol-20dB)	DISC on (IHF-A network) : 2 mW to 55W DISC off (IHF-A network) : 8 mW to 55W
Headphone out	68 mw (at 8 Ω rated output)
Attachment mechanism	Phono1 mm, Phono2 mc indicators Two system Tape terminal Rec Out Selector Output transistor and speaker protection circuit AC outlet Route 3 (switchedx2, unswitchedx1)
Pwer	100 VAC, 50Hz/60Hz
Rated power consumption	160W
External dimensions	Width 435x Height 144x Depth 362 mm
Weight	9.6kg