Audio Database
AM-A70
Commentary

Integrated amplifier equipped with open loop circuit.

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-A70 incorporates 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 amplifier and the I amplifier to improve low-impedance drive capability and circuit stability with a 2-pole DC servo amplifier connected to all stages.

In a simple circuit, the characteristics of the elements appear in the sound as they are, so we use parts carefully selected through thorough hearing tests. We also use transistors, capacitors, and resistors that give excellent sound quality results.
In particular, the use of electrolytic capacitors has been reduced to one third of that of conventional amplifiers in order to reduce the deterioration of sound quality caused by capacitors. Although the equalizer amplifier and V amplifier use independent constant-voltage power supplies, there are only two electrolytic capacitors for smoothing, including this power supply. The I amplifier also has only two electrolytic capacitors except for the protective circuit.

AS-1 for audio is used for the electrolytic capacitor, and fast recovery diode is used for the rectifier circuit for V amplifier / I amplifier.
In addition, high-resolution FBET (folded electrode transistor) is used for the output stage of the V amplifier and the drive stage of power devices, and metalized polyester film capacitors made by Raderstein (ERO) of Germany are used for the DC servo circuit.
In addition, FBET uses a copper heat sink to reduce vibration, and electrolytic capacitors use non-magnetic paint to improve sound quality.

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.

Model Rating
Type Pre-main amplifier
Power Amplifier Unit
Effective power
(20 Hz to 20 kHz, when both channels are driven)
115W + 115W (6 Ω)
100W + 100W (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) 160W
External dimensions Width 440x Height 120x Depth 410 mm
Weight 11.5kg