Audio Database

SU-4600
Commentary

This 2ch/4ch pre-main amplifier was announced as the top-of-the-line 4 ch pre-main amplifier.

The main amplifier section uses a fully complimentary service, all stages of direct-coupled differential-amplification OCL circuit, which eliminates switching distortion that tends to occur at phase transitions, and ensures a flat damping factor up to the DC region. As a result, excellent transient characteristics are obtained from the ultra-low band to the ultra-high band.

The power supply circuits of the output stage and the previous stage are completely separated, and a 10,000 μ F smoothing capacitor is used to eliminate voltage interference and obtain a stable output.
The differential amplifier power supply circuit is also stabilized by a Zener diode.

In order to improve the performance in the ultra low frequency range, the gain is increased by removing the bootstrap capacitor and adding an emitter follower after the differential amplifier.
In addition, by increasing the voltage of the pre-stage power supply circuit to ± 47 v, DC stability is improved and the dynamic range is expanded.

An electronic protection circuit is mounted, and the power supply of the output stage of the main amplifier is controlled by sensing direct current at the output terminal.

In the equalizer section, the first stage differential amplifier is composed of high-voltage and low-noise PNP transistors, and low-noise transistors are also used for the second and third stages to obtain high stability and excellent dynamic characteristics.
In addition, a high DC stability and a wide dynamic range have been obtained by operating with 2 power supplies of ± 43 v.

The tone control circuit employs a two stage direct-coupled differential amplifier circuit with three high-voltage and low-noise transistors. It is a control system that gives frequency characteristics to the amount of NF from the two stage to the differential amplifier. It is also equipped with a tone cancel switch that can quickly obtain flat characteristics.
The tone control circuit is independent for the front and rear, and the adjustment knob uses Klix/Klukš top type.

-12dB/oct. full-scale active filters are used for the high and low filters.

By adopting a ripple filter, shock noise at power-on is prevented.
Two units are installed for the equalizer circuit and tone control circuit in the preamplifier section, and also for the filter amplifier and AFD amplifier.

The AFD control circuit is mounted, and the Matrix 4 ch can be reproduced in the optimum condition.
The phase shift can be switched between 180 °, 90 ° and 0 °.

The main amplifier section can be connected to BTL by switching the switch, and can also be used as a 2-channel high-power amplifier.
In order to protect the amplifier and speaker during BTL operation, a protection circuit using a Sellami star is mounted.

Two 4-ch tape decks can be connected.

Mode switch is mounted.

Equipped with two speaker outputs.

Equipped with 4-ch indicator using LED.

Equipped with front and rear headphone jacks.

Equipped with a 4 ch balancer connection terminal.

There was a wood case sold separately.

Model Rating
Type Solid State 2ch/4ch Pre-main Amplifier
Circuit system Main Part : Complete complimentary service, all stages directly connected OCL circuit
Power Amplifier Unit
Music power
4 ch Operation :
At BTL :
220W (4 Ω)
220W (8 Ω)
Effective power
4 ch Operation :

At BTL :
28Wx4 (4 Ω)
24Wx4 (8 Ω)
56W + 56W (8 Ω)
Power band wiz 5 Hz to 100 kHz (-3dB)
Total harmonic distortion factor 0.2%
Cross modulation distortion factor 0.2%
Signal-to-noise ratio (IHF) 110dB
Damping factor
4 ch Operation :
At BTL :
50 (8 Ω)
20 (8 Ω)
Input Sensitivity / Impedance 1V/50k Ω
Load impedance
4 ch Operation :
At BTL :
4 Ω ~ 16 Ω
8 Ω ~ 16 Ω
Residual noise 1.5mV
Preamplifier Section
Input Sensitivity / Impedance Phono1 : 2mV/50k Ω
Phono2 : 2mV/30k Ω, 50k Ω, 100k Ω
Tuner, Aux1/2, Tape PB : 100mV/80k Ω
Output Level / Impedance Rated output : 1V/10k Ω
Maximum output : 6 V
Rec out : 100mV/500 Ω
Phono maximum allowable input 500mV(RMS)
Frequency characteristic Phono : RIAA deviation ± 0.5 dB
Tuner, Aux1/2 : 5 hz to 70 khz + 0 -3db
Tone control Bass : + 12 to -13dB (50 Hz)
Treble : ± 11 dB (20 kHz)
Loudness control (-30dB) +8dB(100Hz)
Low filter 30 Hz, -12dB/oct.
High filter 8 kHz, -12dB/oct.
Key Features Mono/Stereo/4ch Discrete/4ch Matrix Phase Shifter
AFD Knob (Width, Depth)
Volume knob for each channel
Headphone jack
Preset volume
BTL switch
Phono input impedance selector switch
Pre-out / main in terminal
Circuit protective fuse
4 ch balancer connection terminal
<Others>
Semiconductor used Transistor : 76
Diode : 13 pcs
AC outlet Switched : one system
Unswitched-One system
Power supply voltage 100 VAC, 50Hz/60Hz
Power consumption 110W
External dimensions Width 410x Height 140x Depth 350 mm
Weight 12.6kg
Sold Separately Wood Case SH-747 (¥ 4,800)