Audio Database

AU-9900
Commentary

This pre-main amplifier has improved audio characteristics and operability by adopting a unique chassis structure.

The AU 9900 has a partitioned layout with the preamplifier and tone control located on the front panel side, and the power and power supplies such as heat sinker and power transistor located on the rear side.
As a result, each function and operation are integrated into a single pre-main amplifier an independent state, reducing mutual interference.

The input terminals for players and other devices are installed on the front right side panel, and the output terminals for speakers are installed on the left side panel, so that the signal flow can be smoothly amplified along the shortest path.
In addition, the input terminal, selector switch and equalizer amplifier are close to each other, reducing the shielding wire and preventing the degradation of high-frequency characteristics due to stray capacitance.

The power amplifier section uses a fully connected pure complimentary service OCL system with a differential-amplifier circuit at the input stage.
The output stage employs a parallel push-pull circuit that provides sufficient power at a low distortion rate.

The input circuit of the equalizer section consists of two amplifiers, a flat amplifier and an equalizer amplifier, with a differential amplifier circuit using dual transistors.
The RIAA correction is a CR + NF type that independently performs high-pass and low-pass operations, and provides more accurate RIAA and phase characteristics.

Equipped with triple tone control that allows mid-range control in addition to normal tone control.
The tone selector switches the turnover frequency between three low and three high levels.

A highly regulated and efficient toroidal transformer is used for the power supply.
A large capacity capacitor and a stabilized power supply circuit are combined to supply a stable ± power supply to each block stage.

Temperature detection, DC detection and ASO detection current limiter circuit is adopted for the protection circuit to protect the speaker and power transistor.

Equipped with a tone defeat switch that passes through the tone circuit and provides a flat frequency response.

The volume level can be set to 0 dB, -10dB or -20dB.

Equipped with a 2-circuit tape play circuit, tape copy switch, tuner priority selector, low / high filter, muting switch, input impedance and sensitivity selector switch.

Model Rating
Type Pre-main amplifier
Effective output (both channel operation) 80W + 80W (4 ω, 8 ω, 20 Hz to 20 kHz)
80W + 80W (4 Ω, 8 Ω, 1 kHz, THD 0.05% or less)
Total harmonic distortion factor (rated output) Not more than 0.08%
Intermodulation Distortion Factor (70 Hz : 7 kHz = 4 : 1, SMPTE) Not more than 0.08%
Frequency Response (at 1W) 10 Hz to 50 kHz + 0 -1dB
Damping factor 80 (8 Ω)
RIAA deviation (30 Hz to 15 kHz) ± 0.3 dB
Load impedance 4 Ω, 8 Ω
Channel Separation (1 kHz) Phono1 and 2 : 55 dB or more
Tuner, Aux1, 2, Tape Monitor : 60 dB or higher
Hum and noise (IHF) Phono1, 2 : 65 dB or more
Tuner, Aux1, 2, Tape Monitor : 80 dB or higher
Input Sensitivity / Impedance (1 kHz) Phono1 : 2 mV, 4 mV, 8mV/30k Ω, 50k Ω, 100k Ω
Phono2 : 2mV/50k Ω
Tuner, Aux1, 2, Tape Monitor1 : 130mV/50k Ω
Tape Monitor2(Pin/Din):130mV
Maximum allowable input (1 kHz, THD 0.1% or less) Phono1 : 1000 mV (Input Sensitivity Switching 8 mV)
Phono2:300mV
Aux, Tuner : 3 v
Output level Tape rec1(Pin):130mV
Tape rec2(Pin/Din):130mV/30mV
Tone control Bass : ± 10 dB (30 Hz)
Midrange : ± 5 dB (1.5 kHz)
Treble : ± 10 dB (20 kHz)
Tone selector Bass : 150 Hz, 300 Hz, 600 Hz
Treble : 2 kHz, 4 kHz, 8 kHz
Low filter -3dB at 20 Hz, 12dB/oct.
-3dB at 60 Hz, 12dB/oct.
High filter -3dB (7 kHz), 6dB/oct.
-3dB at 12 kHz, 12dB/oct.
Rated power consumption 180W
External dimensions Width 460x Height 160x Depth 375 mm
Weight 17.9kg