Technics SU-3400
¥ 59,000 (around 1973)
Commentary
Pre-main amplifier developed based on Technics 50A and SU-3600.
The final stage of the power amplifier employs a complete complimentary service circuit in which NPN type transistors that operate with a + signal and PNP type transistors that operate with a - signal are to drive while inverting the phases.
Switching distortion that tends to be seen in conventional circuits is eliminated because of the smooth configuration that allows current to flow easily by changing the + - signal.
In addition, all stages are directly connected to the OCL circuit in the power amplifier section to keep the damping factor flat and reduce the distortion factor.
In order to make the most of the circuit characteristics, a differential amplifier using a pair of low-noise PNP transistors with uniform characteristics is adopted at the first stage. Moreover, the common emitter circuit of the differential amplifier is composed of a direct-coupled circuit using a constant current circuit to obtain high stability.
The equalizer stage consists of three stages of PNP-NPN-PNP directly connected circuits. The first stage uses a specially selected low-noise PNP transistor to obtain a large gain and greatly improve the SN ratio.
The curve change point of the tone control can be switched in two stages each for bass and treble, and the tone control can be adjusted separately for the left and right channels.
This tone control is a special combined structure consisting of a resistor and a silver conductor. It is a two volume type of technics that can be used separately for raising and lowering. When one of the tone controls touches the resistor, the other touches the silver conductor, so that only one capacitor is inserted.
At the midpoint, both brushes come on top of the silver conductor, so you get completely flat and straightforward characteristics.
In addition, it has excellent distortion characteristics with 2-stage direct connection circuit configuration.
The volume is a preset volume.
If you preset the volume to an appropriate level, the knob will stop rotating at that position.
Two tape decks can be connected, and recording and dubbing of two tapes simultaneously is possible.
The input impedance of the Phono input terminal can be switched to 3 levels.
It is equipped with a unique speaker protection circuit that detects DC current so as not to burn the voice coil due to DC current flowing through the speaker.
We also provide circuit protection devices to prevent transistors from being damaged due to miswire connections or other operational errors.
Easy-connector type speaker terminal is used.
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Model Rating
| Type | Solid state pre-main amplifier |
| Circuit system | Complete complimentary service all-stage direct-coupled OCL circuit |
| Power Amplifier Unit | |
| Music Power (IHF) | 120W (4 Ω) 90W (8 Ω) |
| Effective power (IHF) | 42W/42W (4 Ω) 35W/35W (8 Ω) |
| Power Band Wiz (Strain 0.2%) | 5 Hz to 50 kHz, -3dB |
| Frequency characteristic | 5 Hz to 100 kHz, + 0 -3dB |
| Distortion factor (at effective output) | Not more than 0.2% |
| Intermodulation distortion factor (60 hz : 7 khz = 4 : 1) | 0.2% or Less (Effective Output) |
| Signal-to-noise ratio (IHF) | 110 dB or more |
| Damping factor | 50 (at 8 Ω Load) |
| Input Sensitivity / Impedance | 1V/50k Ω |
| Preamplifier Section | |
| Input Sensitivity / Impedance | Phono : 2mV/30, 50, 100k Ω Tuner : 100mV/80k Ω AUX : 100mV/80k Ω |
| Tape Monitor 1, 2 | Rec Out : 100mV/10k Ω Playback : 100mV/60k Ω Rec/Play (DIN) : 100mV/60k Ω, 50mV/80k Ω |
| Output Voltage / Impedance | Rated output : 1V/200 Ω Maximum output voltage : 3 V |
| Phono maximum allowable input | 100mV(1kHz) |
| Frequency characteristic | Phono : within ± 0.5 dB deviation from the RIAA standard curve Tuner : 5 hz to 60 khz, + 0 to 3 db AUX : 5 Hz to 60 kHz, + 0 -3dB |
| Tone control | Bass : 50 Hz, + 16 dB to -16dB Turnover frequencies : 150 Hz, 500 Hz Treble : 20 kHz, + 14 to -14dB Turnover Frequencies : 2 kHz, 6 kHz |
| Loudness control | 100 Hz, + 10 dB (Volume -30dB) |
| <General> | |
| Semiconductor used | Transistor : 32 Diode : 7 |
| Pwer | 100 VAC, 50/60Hz |
| AC outlet | Switched : 1 system Unswitched : 1 line |
| Power consumption | Rated output : 70W |
| External dimensions | Width 410x Height 140x Depth 300 mm |
| Weight | 10.2kg |