Audio Database

AU-5500
Commentary

This is a pre-main amplifier that uses triple tone control and complete defeat system to improve practical performance and sound quality.

A differential amplifier circuit in which a pair transistor capable of stable amplification is combined at the first stage of the power amplifier section is adopted.
A 3-stage Darlington connection circuit is used for the drive stage, and a heteropolar power transistor with uniform characteristics is used for the final output stage.

A high-gain monolithic dedicated IC is used for the equalizer amplifier. Because of the high gain, a large NFB is applied, resulting in flat characteristics and a wide frequency band.

In addition to Bass and Treble, the tone amplifier uses triple tone control with adjustable Midrange.
This circuit is an NF type circuit that uses a selected low-noise noise type transistor for the first stage input, and flat characteristics can be obtained by fully disabling the tone control circuit.

The chassis ground is not used for grounding at the input of the equalizer amplifier without using chassis ground.
As a result, each circuit operates normally and stability is improved.

It is equipped with a low filter that cuts out scratching noise and harsh noise in the high range, and a low filter that cuts out grounders in the low range.

A large power transformer with good regulation is used for the power supply.
A stabilizing power supply is supplied to the equalizer amplifier and tone amplifier.

Uses a protective circuit that combines an electronic circuit, a relay, and a short-cut fuse.
The detection circuit is an over-protected circuit with high reliability, such as an ambient temperature detection circuit for power transistors and an abnormal voltage detection circuit for speaker protection.
It also prevents pop noise when the power is turned on.

It is equipped with 2 systems of tape monitors, and it is possible to copy tapes 1 → 2 or 2 → 1 by using 2 units.

Equipped with a loudness switch that is convenient for low volume.

Equipped with an audio muting switch that operates at -20dB with one switch.

Equipped with a stereo / monaural mode selector switch.

The speaker can be switched OFF/A/B/A + B.

Equipped with a pre-main disconnect switch.

Equipped with DIN outlet.

Equipped with large grounding terminal and spare AC outlet.

Model Rating
Type Pre-main amplifier
Effective power
Both channel operation 20 Hz to 20 kHz : 30W + 30W (8 Ω)
1 kHz : 35W + 35W (8 Ω)
Single channel operation 1 kHz : 38W/38W (8 Ω)
Music power 130W (4 Ω, 1 kHz)
Total harmonic distortion factor Pre Amp : 0.1% or less
Main Amp : 0.1% or less
Over All : 0.15% or less
Intermodulation Distortion Factor (70 Hz : 7 kHz = 4 : 1, SMPTE) Pre Amp : 0.1% or less
Main Amp : 0.1% or less
Over All : 0.2% or less
Power Band With (IHF) 5 Hz to 30 kHz
Frequency response (at 1W output) 10 Hz to 35 kHz + 0.5 -1dB
RIAA deviation (30 Hz to 15 kHz) ± 0.5 dB
Damping factor 30 (8 Ω)
Input Sensitivity / Impedance Phono : 2.5mV/50k Ω
Tuner, AUX, Tape Monitor (Pin/Din) : 100mV/50k Ω
Main Amp : 800mV/50k Ω
Phono maximum allowable input (THD <0.2%) 200mV
Output Voltage (1 kHz) Tape Rec(Pin/Din):100mV/30mV
Pre Amp:800mV
Channel Separation (1 kHz) Phono : 50 dB or more
Tuner/AUX, Tape Monitor : 55 dB or higher
Main Amp : 60 dB or higher
Hum and noise (IHF) Phono : 70 dB or more
Tuner, AUX : 85 dB or higher
Main Amp : 100 dB or higher
Tone control Bass : ± 13 dB (50 Hz)
Midrange : ± 5 dB (1 kHz)
Treble : ± 13 dB (15 kHz)
Loudness (at Volume -30dB) + 10 dB at 50 Hz, + 8 dB at 10 kHz
Low filter 70Hz=-3dB(6dB/oct)
High filter 7kHz=-3dB(6dB/oct)
Muting -20dB
Rated power consumption 70W
External dimensions Width 434x Height 130x Depth 315 mm
Weight 10.4kg