Audio Database


Technics SU-3400
59,000yen(around the 1973 time)

The Integrated Amplifier developed Technics 50A and based on SU-3600.

The last stage of power amplifier has adopted the perfect complementary circuit driven while reversing a phase, combining symmetrically the NPN form which operates by + signal, and the PNP transistor which operates by - signal.
+ At the change of - signal, switching distortion which tended to be seen in the conventional circuitry is canceled for the impossible stream composition into which it is easy to flow through an electric current and which is not.
Moreover, the distortion is lessened, while having adopted the whole page hardwired-connection OCL circuitry as a power amplifier part and maintaining a dumping factor at a flat.

In order to make use of the property of a circuitry, the differential amplifier which uses in a pair the low noise PNP transistor to which the property was equal to the first rank is adopted, and moreover, the common-emitter circuitry of the differential amplifier was constituted from a hardwired-connection circuitry which used the constant current circuit, and has acquired high stability.

The equalizer stage serves as circuitry of the 3 steps of PNP-NPN-PNP hardwired connection, and especially the first rank used the low noise PNP transistor selected carefully, took large gain, and has improved the SN ratio sharply.

the changing point of a curve of a tone control a bass and each treble it can switch to a two-step and the tone control can rectify a channel on either side separately.
the object for an elevation for - descent of the special structure with which this tone control combined the resistor and the silver conductor -- are a technics type Dual-unit volume scheme used separately, and while one side is touching the resistor, another side touches a silver conductor -- always -- while is a mechanism in which only the capacitor is inserted.
Since both of brushes come on a silver conductor at the middle point, a property completely gentle in a flat is acquired.
Moreover, the distorted property is excellent in the circuitry of a two-step hardwired connection.

The preset volume is adopted as a volume.
If the volume is preset on suitable level, the rotation of a knob serves as the mechanism of stopping at the location.

A two-set interconnection of a tape deck is possible, and a sound recording with two simultaneous sets and dubbing are also possible.

Three-step switching of the input impedance of a Phono input terminal is possible.

A direct current flows into a speaker, and the peculiar speaker protection network which detects a direct current is carried so that a voice coil may not be damaged by fire.
Moreover, by the mistake on usings, such as a connection mistake, the circuit-protection unit for preventing that a transistor etc. is damaged was also arranged, and perfectness is measured.

The easy connector type speaker termination is adopted.


Rating of a mode
Form Solid-state Integrated Amplifier
Circuit system Perfect complimentary whole page hardwired-connection OCL circuitry
<Power amplifier part>
Music power (IHF) 120W (4ohms)
90W (8ohms)
Effective output (IHF) 42W/42W (4ohms)
35W/35W (8ohms)
Power Band Width (0.2% of distortion) 5Hz - 50kHz-3dB
Frequency characteristic 5Hz - 100kHz, and +0 -3 dB
Distortion (at the time of an effective output) 0.2% or less
Cross modulation distortion (60Hz:7kHz=4:1) 0.2% or less (at the time of an effective output)
S/N ratio (IHF) 110dB or more
Dumping factor 50 (at the time of an 8-ohm load intensity)
Input sensitivity/impedance 1V/50kohm
<Preamplifier part>
Input sensitivity/impedance Phono: 2mV/30, 50, 100kohm
Tuner: 100mV / 80kohm
AUX: 100mV / 80kohm
Tapes monitors 1 and 2 Rec Out: 100mV / 10kohm
Playback: 100mV / 60kohm
Rec/Play(DIN): 100mV / 60kohm, 50mV / 80kohm
An Output voltage/impedance Output power: 1V/200 ohm
Maximum output voltage: 3V
Phono maximum permissible input 100mV(1kHz)
Frequency characteristic Deflection of less than ±0.5dB from a Phono:RIAA standard curve
Tuner: 5Hz - 60kHz, and +0 -3dB
AUX: 5Hz - 60kHz, and +0 -3dB
Tone control Bass: 50Hz, +16dB--16dB
Turnover frequency: 150Hz, 500Hz
Treble: 20kHz, +14--14dB
Turnover frequency: 2kHz, 6kHz
Loudness control 100Hz, +10dB (Volume-30dB)
The semiconductor used Transistor: 32
Diode: Seven
Power source AC100V, 50/60Hz
AC outlet Switched: One line
Unswitched: One line
Power consumption At the time of an Output power: 70W
Dimensions Width 410x height 140x depth of 300mm
Weight 10.2kg