Audio Database

AU-6600
Commentary

This pre-main amplifier has been developed taking over the basic performance of the advanced AU 7700.

By using a back panel with a unique structure, the input terminal is mounted facing up and directly connected to the equalizer board at the shortest distance. This eliminates the use of shielding wires, which degrade the high-frequency characteristics, and improves the SN ratio.

In conventional amplifiers, the chassis was used as a common ground for each circuit, but this affected the sound quality due to current interference.
The AU 6600 provides one point grounding near the equalizer amplifier to improve sound quality.

The first stage of the power amplifier section employs a pure complimentary service OCL circuit directly connected to all stages. To maintain the 0 VU potential of the output point, a highly stable differential amplifier and bias compensation circuit are employed. The drive stage is composed of three stage Darlington connection with carefully selected transistors.
In addition, a large heat sinker is installed in the lower part of the input terminals on the back panel, and as a result of putting it out of the amplifier, the heat radiation effect becomes good, and large output with allowance is obtained.

The first stage input of the equalizer amplifier uses a stable differential amplifier circuit with ± power supply. It has a stable DC balance and excellent features such as high dynamic range, high S/N ratio and low distortion.
We have also obtained excellent characteristics by carefully selecting high-precision CRs for NFB elements.
Since the potential of the input / output circuit is approximately 0 V, unpleasant click noise generated when the selector switch is switched is prevented.

The tone control is an NF type using Klix/Klukš top type elements with high precision and good feeling.
The tone amplifier has a 5-chip configuration using a differential amplifier circuit with ± power supply at the first stage.
In addition to Bass and Treble, you can also adjust the Midrange triple tone control to obtain the optimum tone control characteristics according to your preference.

Equipped with a tone selector switch that can switch the roll off and turnover frequency of Bass and Treble respectively.

Equipped with tone defeat, it bypasses the tone control circuit and provides flat frequency characteristics.

Equipped with high filter and low filter.

The power supply section is equipped with a power-supply block such as a heavy-duty transformer and silicon diode.
The equalizer amplifier and tone amplifier are supplied with ± power from a stabilizing power supply circuit.

It is equipped with a protective circuit combining an electronic circuit and a relay.
Speaker protection at the output point Using voltage detection circuit and overcurrent detection circuit, it can cope with the self such as operation error.
It also serves as a circuit to prevent the pop noise that occurs when the power is turned on.

The tape monitor is equipped with 2 circuits so that you can monitor during tape copying and recording.

Equipped with a speaker selector switch, A and B can be output individually or simultaneously.

Equipped with a pre-main disconnect switch, each can be used independently.

It is equipped with spare AC outlet and large earth terminal.

It is equipped with a loudness switch, muting switch, stereo / mono switching mode switch, etc.

Equipped with headphone jack.

Equipped with DIN outlet.

Model Rating
Type Pre-main amplifier
Effective power
Both channel operation 20 Hz to 20 kHz : 40W + 40W (8 Ω)
1 kHz : 45W + 45W (8 Ω)
Single channel operation 1 kHz : 48W/48W (8 Ω)
Music power 190W (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 : 0.15% or less
Power Band With (IHF) 5 Hz to 35 kHz
Frequency response (at 1W output) 10 Hz ~ 40 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%) 300mV
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)
Tone selector Bass:300Hz/600Hz
Treble:2kHz/4kHz
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 90W
External dimensions Width 434x Height 130x Depth 315 mm
Weight 11.3kg