AKAI AM-A90
¥ 99,800 (released in 1986)
Commentary
Integrated amplifier designed to simplify the circuit completely.
It is equipped with an open loop circuit that pursues simplicity without relying on NFB.
This circuit eliminates the overall NFB loop, the basic configuration of the amplifier is simple with only two stages : a voltage stage (V amplifier) and a current stage (I amplifier), and a parallel push-pull two stage Darlington configuration with two power transistors per channel.
The AM-A90 is equipped with a discrete open-loop circuit for the phono equalizer amplifier and main amplifier. In addition, AKAI's own 0 drive circuit is inserted between the V and I amplifiers to improve low-impedance drive capability and circuit stability with a 2-pole DC servo amplifier connected to all stages.
In the AM-A90, the output stage of the power amplifier is a parallel push-pull configuration using two MOS-FETs per channel. This is driven by a high-resolution FBET (folded electrode transistor) to eliminate the cause of sound quality degradation.
This MOS-FET is fixed to a large aluminum heat sink by means of a highly heat-conductive insulating sheet with little secular change.
The power supply section uses a large toroidal transformer with high regulation and leakage flux countermeasure.
AS-1 for audio is used for the electrolytic capacitor, fast recovery diode is used for the rectifier circuit for V and I amplifiers, and metalized polyester film capacitor of Raderstein (ERO) is used for the DC servo circuit.
Equipped with a line straight-through switch, you can jump the tone control circuit.
The input / output terminal for video is mounted.
A buffer amplifier is installed on the video connector to reduce noise.
Equipped with a REC selector that can be used independently of the input selector.
Equipped with a 2-channel speaker selector switch.
Equipped with MC cartridge selector switch.
Equipped with a -20dB muting circuit.
Equipped with a subsonic filter and loudness.
Aluminum front panel is used for the front panel.
Gold plated terminals with excellent conductivity and aging resistance are used for all input / output terminals.
Uses a oxygen-free copper power cord with polarity indication.
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Model Rating
| Type | Pre-main amplifier |
| Power Amplifier Unit | |
| Effective power (20 Hz to 20 kHz, when both channels are driven) |
145W + 145W (6 Ω) 130W + 130W (8 Ω) |
| Total harmonic distortion factor | 0.7% (20 Hz to 20 kHz) 0.5% (8 Ω, Effective Output) |
| Output Bandwidth (IHF) | 10 Hz to 80 kHz |
| Damping factor | 30 (1 kHz, 8 Ω) |
| Frequency characteristic | 5 hz to 100 khz -3dB |
| Preamplifier Section | |
| Input Sensitivity / Impedance | Phono MM : 2.0mV/47k Ω Phono MC : 0.2mV/100 Ω CD, Tuner, Tape : 150mV/47k Ω VTR, V. Disc (audio) : 150mV/47k Ω VTR, V. Disc (video) : 1Vp-p/75 Ω |
| Phono maximum allowable input (1 kHz) | MM:250mV MC:25mV |
| Output Level / Impedance | Tape rec : 150mV/1k Ω VTR rec (audio) : 150mV/1k Ω VTR rec (video) : 1Vp-p/75 Ω Monitor out (video) : 1Vp-p/75 Ω |
| S/N ratio (IHF-A) | Phono MM:86dB Phono MC:67dB CD, Tuner, Tape : 100 dB |
| <General> | |
| Rated power consumption (Electrical Appliance and Material Control Law) | 195W |
| External dimensions | Width 440x Height 120x Depth 410 mm |
| Weight | 12.5kg |