YAMAHA A-1000

Commentary

Pre-main amplifier that uses Dual Amp Class A circuit and ZDR circuit.

The basic circuit configuration of the A-1000 is the same as that of the A-2000. It is a class A power amplifier using a DC servo NF-CR real-time equalizer with twin RIAA elements, a Richness circuit, and Dual Amp Class A with ZDR.
When the richness circuit is turned OFF and the direct switch is turned ON, it passes through the tone control circuit and becomes a pre-main direct connection. It is also designed with an emphasis on CD. The CD input is directly input to a power amplifier with 150 mV sensitivity via a function switch.

Dual Amp ClassA circuit used for B-2x and A-2000 is used.
This circuit consists of a class A amplifier and a class AB amplifier. The load is connected to each output of the class A amplifier and the class AB amplifier, and the NFB is connected to the class A amplifier from both ends of the load. Thus, the class A amplifier completely controls the load current, so that the amplifier as a whole operates as class A, while the class AB amplifier only takes charge of power loss.
As a result, a high-power A class drive of the whole amplifier output area is realized.

The Dual Amp Class A circuit is equipped with Yamaha's original ZDR circuit (Zero Distortion Rule), which eliminates slight distortion caused by non-linearity of the element and realizes excellent linearity.

The Dual Amp Class A system installed in the A-1000 uses a non-current ground that only determines the electric potential and does not allow current to flow to the ground, which fundamentally solves the grounding problem.
In addition, like the A-2000, the common impedance is made to be 0 in the circuit. In addition to the power stage and the current, each circuit such as the preamplifier and the transformer system is completely separated to provide one point grounding.

The power supply unit has a hyperfractionation multi-terminal structure with an emphasis on sound quality, and is equipped with a total capacity of 146,000 μ F.

The preamp section is a separate power source from the power amplifier section, and uses Yamaha's original pure current dam system, which uses two units of 1,000 μ F each.
The equalizer circuit consists of an NF-CR type Dual RIAA element. The CR type compensates for the disadvantages of the conventional NF type to obtain a more accurate RIAA curve. In addition, this method requires only a small amount of NF in the high-frequency range, so the phase correction is light and the operation of the equalizer amplifier becomes extremely stable.
The circuit configuration of this equalizer is a direct-coupling DC servo system using a high gm low-noise FET.

It is equipped with a richness circuit that can correct sound quality.
This circuit is a type of low-pass equalizer circuit that can flatly extend the low-frequency response of the speaker down one octave.
This circuit can be switched between 3 positions of NS-2000 only, NS-1000/NS-1000X only, general purpose, and ON-OFF.

Equipped with an accessory terminal to which graphic equalizers and surround amplifiers can be connected.

The exterior uses a 800 μ m mirror finished real wood walnut sideboard with four times the same polyester paint as the grand piano.

Quality parts such as a large-capacity electrolytic capacitor with a multi-terminal structure of hyperfractionation foils, a polarized 10 mm φ extra-thick power cord using oxygen-free copper wires, internal wiring using many oxygen-free copper wires, large speaker terminals capable of using monster cables, gold-plated Phono / CD terminals, and low-resonance heat sink using extruded material are adopted.

Model Rating

Type	Pre-main amplifier
Rated Output (20 Hz ~ 20 kHz)	140W + 140W (4 Ω, 0.005% strain) 120W + 120W (6 Ω, 0.003% strain) 100W + 100W (8 Ω, strain 0.003%)
Power bandwidth	10 Hz ~ 100 kHz (50W, 8 Ω, Distortion 0.02%)
Damping factor	200 or More (1 kHz, 8 Ω)
Input Sensitivity / Impedance	Phono MC : 160 μ V/220 Ω Phono MM : 2.5mV/47k Ω Aux : 150mV/47k Ω
Output Voltage / Impedance	Rec out : 150mV/330 Ω
Total harmonic distortion factor	0.005%(Phono MC - Rec out) 0.003%(Phono MM - Rec out) 0.003% (Aux/etc-SP out/8 Ω)
RIAA deviation	MC/MM : 10 Hz to 100 kHz ± 0.5 dB MM : 20 Hz to 20 kHz ± 0.2 dB MC : 20 Hz to 20 kHz ± 0.3 dB
S/N ratio (IHF-A)	Phono MC : 72 dB (equivalent to 250 μ V input) Phono MM:86dB(2.5mV) Aux, etc : 108 dB Main in:124dB
Tone control	Bass : ± 10 dB (20 Hz), 350 Hz Treble : ± 10 dB (20 kHz), 3.5 kHz
Subsonic filter	Low : 15 Hz, -12dB/oct.
Richness	Position 1 (for NS-2000) : + 7.5 dB at 30 Hz Position 2 (for NS-1000) : + 7.5 dB at 40 Hz Position 3 (general) : + 7.5 dB (50 Hz)
Pwer	100 VAC, 50Hz/60Hz
Power consumption	305W
External dimensions	Width 473x Height 159x Depth 434 mm
Weight	16.5kg