YAMAHA AX-2000
¥ 230,000 (released in 1987)
Commentary
Stereo pre-main amplifier with built-in D/A converter equipped with advanced digital direct function.
In order to reproduce the digital source in high quality, it is equipped with the advanced digital direct function which improves the SN at the actual use volume level of around -22dB which is normally heard.
The output of the built-in D/A converter unit is a high-level signal of 7.5 vrms instead of 2.0 vrms, and the gain of the amplifier in the latter stage is reduced. This greatly improves the SN of the amplifier system.
The AX-2000 consists of an active volume of up to + 22.5 dB, a tone amplifier of 11.5 dB, and a power amplifier of 12 dB. When the digital direct switch is turned on, the tone amplifier is bypassed, and the signal amplification transmission system is simple and straight with only active volume and power amplifier.
The volume controller uses an active volume with a combination of variable resistor and linear amplifier.
This improves the S/N ratio in actual use by limiting the volume to the maximum value and reducing the noise level as the volume is reduced.
The D/A converter section is equipped with a Yamaha high-bit system (8 fsx 18-bit digital filter, 18-bit operation twin D/A converter).
In a high-bit system, the sampling noise is shifted to a much higher frequency range, and is suppressed to a practically negligible level by the aperture effect of the D/A converter itself, so that a pure DAC direct output without a low-pass filter is possible.
Direct playback is available for 7.5 v high-level D/A output, filtered playback is available for 2.0 v normal D/A output, and clearer sound quality is obtained with the Advanced Digital Direct function.
Yamaha's original HCA circuit is used for the power amplifier.
This eliminates discontinuity in stiffness characteristics by converting input signals into positive and negative hyperbola characteristics, and guarantees class A operation for all power and load.
Hi-f for output stageTTriple parallel push-pull configuration with power transistor is adopted.
In the power amplifier section, the heat sinker of both LR channels and the power amplifier circuit board are arranged symmetrically with the power transformer at the center, and the structural and weight balance is maintained to suppress the sound quality degradation.
The power amplifier circuit power amplifier circuit board is installed on the opposite side of the power transformer with the heat sinker interposed between it and the non-magnetic side wood panel side to avoid magnetic strain.
In order to prevent degradation of sound quality due to unnecessary radiation from the digital part, we have adopted 2 box construction in which the digital part and the preamplifier part are independent from each other.
In addition, by using the copper plated chassis / frame entirely, the generation of magnetic strain is eliminated and vibration resistance is improved.
Equipped with MC/MM independent phono equalizer amplifier.
Input / Rec Out is a semiconductor selector using FET with low distortion factor and low leak specification, and is switched near rear input / output terminal.
By eliminating the routing of the internal wiring that causes the audio signal to go back and forth between the front and rear, deterioration of sound quality is prevented in advance.
The power supply section is equipped with a 420 VA power transformer with shield case and a 27,000 μ Fx2 large-capacity aluminum electrolytic capacitor for audio.
Considering not only the size of electrical capacity but also the effect of size and weight on sound generated, the transformer is designed to be heavier, and the capacitor is enlarged to 76 φ to obtain excellent power supply capacity.
The power amplifier section, analog section, digital system, visual system and control & display system are equipped with independent windings. The Line 5 independent power source system is adopted to eliminate mutual interference.
Especially for analog and digital power supplies, high-speed Schottky diodes are used as rectifying elements to suppress the generation of harmful pulse-like noise.
In addition, the visual system power supply can be turned on and off independently, and can be used separately for pure and AV.
In addition, the digital master clock is designed to automatically stop when the analog source is selected (including when the analog input of the digital source is selected).
Digital input jacks are installed in addition to analog input jacks on the four inputs of CD, DAT1, DAT2 and VDP/DBS.
In addition, DAT1 and DAT2 are equipped with digital REC out jacks.
The digital input terminal automatically follows the sampling frequency of 32k/44.1k/48kHz.
The CD digital input and and DAT1 Digital Drive are equipped with two terminals that are coaxial with the light. They can be used according to preference. When used in parallel, the light is automatically given priority.
Equipped with video input of Route 3.
Equipped with 3-band tone control with tone jump, balance control, stereo / mono mode switching, subsonic filter, headphone jacks and accessory jacks.
It comes with a remote controller that allows input switching and volume control.
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Model Rating
| Type | Pre-main amplifier |
| Amplifier Unit | |
| Rated Output (20 Hz ~ 20 kHz) | 190W + 190W (4 Ω, 0.005%) 150W + 150W (6 ohm, 0.003%) 130W + 130W (8 Ω, 0.003%) |
| Dynamic Power | 600W + 600W (1 ohm) 500W + 500W (2 Ω) 240W + 240W (6 Ω) |
| Damping factor (1 kHz, 8 Ω) | 200 |
| Input Sensitivity / Impedance | Line In : 150mV/47k Ω |
| Output Voltage / Impedance | Rec Out : 150mV/680 Ω |
| Practical SN ratio (Vol -22.5 dB, IFF-A) | Normal : 116 dB (2 V input) Digital Direct : 128 dB (7.5 V input) |
| Residual Noise (IHF-A) | Normal : 23 μ V Digital Direct : 7 μ V |
| Channel Separation (1 kHz, Vol -22.5 dB) |
Normal : 80 dB (5.1k Ω termination) Digital Direct : 100 dB |
| Tone control | Bass : 20 Hz, ± 10 dB (turnover Frequency : 350 Hz) Treble : 20 kHz, ± 10 dB (turnover : 3.5 kHz) Mid : 1 kHz, ± 10 dB (Center Frequency : 1 kHz) |
| Subsonic filter | 15 Hz, -6dB/oct. |
| Audio Mute | -20dB |
| Phono Equalizer Section | |
| Input Sensitivity / Impedance | MC : 100 μ V/100 Ω MM : 2.5 μ V/47k Ω |
| Maximum Allowable Input (1 kHz, 0.01%) | MC:6mV MM:140mV |
| Signal-to-noise ratio | MC : 83 dB (250 μ V, input short) MM : 90 dB (2.5 mV, input short) |
| RIAA deviation | MC, MM : + / - 0.2 dB |
| Harmonic distortion factor (20 Hz to 20 kHz at 3 V output) | MC, MM : 0.003% |
| Channel Separation (1 kHz, Input Short) | MC, MM : 80 dB |
| D/A Conversion Unit | |
| Output Voltage (0 dB Signal Input) | Normal, Rec Out output : 2 V Digital Direct Output : 7.5 V |
| Harmonic distortion factor (EIAJ) | Not more than 0.002% |
| Dynamic Range (EIAJ) | 100 dB or more |
| Signal-to-noise ratio (EIAJ) | 118dB |
| Channel Separation (1 kHz) | 100dB |
| <General> | |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 350W |
| External dimensions | Width 473x Height 170x Depth 475 mm |
| Weight | 28kg |
| Attachment | Remote Controller RS-AX2000 |