YAMAHA AX-2000A
¥ 240,000 (released in 1990)
Commentary
This is a top-of-the-line pre-main amplifier that thoroughly seeks the best analog quality and continues with pure audio.
The MEGA-SN (Most Effective Gain Arrangement for Signal to Noise Ratio) circuit with balanced amplifier gain is adopted to improve the SN degradation in the volume by adopting an active volume (maximum gain + 22.5 dB) with a high-performance linear amplifier and variable resistor. The MEGA-SN (Most Effective Gain Arrangement for Signal to Noise Ratio) circuit with balanced amplifier gain is adopted. This greatly improves the SN in actual use.
The AX-2000A is equipped with a MEGA - direct-in circuit which is based on the MEGA-SN circuit and further improves SN.
In this circuit, an ultra-low noise direct amplifier is provided immediately after the input terminal instead of canceling the tone amplifier. This improves the SN ratio while maintaining the total gain.
The direct amplifier, which is important for this circuit, adopts a capacitor division type using C (capacitor) as a gain setting element, and adopts an ultra-low-noise dual FET configuration at the first stage of the amplifier.
As a result, the gain after the volume is only 12 dB of the power amplifier. At the Vol min point, the SN ratio is further improved by 11.5 dB compared to the MEGA-SN circuit.
Equipped with a Canon terminal with level switching of + 4 dBm for professional equipment, business CD player and DAT can be connected as it is. Equipped with a Canon-Pin selection switch, it can be connected to Para for sound comparison.
Class A operation using HCA circuit is adopted for the power amplifier section.
This is the I of Tr.C-VBEBy utilizing the logarithmic characteristic of the characteristic as it is, it is possible to perform class A hyperbolic conversion (HC) operation without cutting off at all outputs. It does not depend on idling current, and with a simple configuration of two dual Trs, full load and full output pure class A operation is realized.
As a result, class A operation is possible without cut-off even under low load such as 1 Ω in addition to low distortion, and drive capability not affected by the impedance of the speaker is obtained.
The power supply section contains a large power transformer with a shield case of 420 VA, and an aluminum electrolytic capacitor of 27,000 μ Fx2 for audio.
In order to maintain structural and weight balance, the power amplifier section is placed symmetrically on the left and right side of the power transformer, and the circuit board is placed on the outermost side in contact with the wood panel to solve the problem of magnetic strain.
In addition, the pre-part and control part are two independent boxes to prevent mutual interference, and copper plated chassis and frame are fully adopted.
Equipped with MC/MM independent dedicated equalizer amplifier.
Since the input is switched after amplification, deterioration of the signal quality is minimized.
The input and Rec Out selectors are switched directly behind the input / output terminals by a discrete electronic switch of low distortion rate specification.
As a result, there is no need to route wiring with a small signal, and degradation of sound quality is minimized.
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Model Rating
| Type | Pre-main amplifier |
| Rated Output (20 Hz ~ 20 kHz) | 150W + 150W (6 Ω, 0.003% strain) |
| Dynamic Power | 600W + 600W (1 ohm) 500W + 500W (2 Ω) 240W + 240W (6 Ω) |
| Input Sensitivity / Impedance | Phono MC : 100 μ V/1k Ω Phono MM : 2.5mV/47k Ω CD, etc : 150mV/47k Ω Accessory In : 150mV/47k Ω Direct In (unbalanced) : 150mV/47k Ω Direct In (balanced / normal) : 150mV/40k Ω Direct In (Balanced Pro Course) : 1.23V/40k Ω |
| Maximum allowable input (1 kHz, Distortion 0.01%) |
MC:6mV MM:140mV |
| Frequency characteristic | 20 Hz ~ 20 kHz ± 0.2 dB (All Input) |
| Total harmonic distortion factor | 0.003% (MC, MM → Rec Out, 20 Hz to 20 kHz, 3 V) |
| S/N ratio (IHF-A) | Phono MC : 83 dB (250 μ V) Phono MM:90dB(2.5mV) |
| Residual Noise (IHF-A) | 23 μ V (normal, Vol - ∞) 7 μ V (Direct, Vol - ∞) |
| Tone control | Bass : ± 10 dB (20 Hz, turnover frequency 350 Hz) Mic : ± 10 dB (1 kHz, turnover frequency 1 kHz) Treble : ± 10 dB (20 kHz, turnover frequency 3.5 kHz) |
| Subsonic filter | 15 Hz, -6dB/oct. |
| Power consumption | 300W |
| External dimensions | Width 473x Height 170x Depth 475 mm |
| Weight | 28kg |
| Attachment | Remote control |