Technics SU-C04
¥ 41,800 (around 1981)
Commentary
This is a Concise Integrated Amplifier equipped with a Technics original linear feedback circuit that realizes theoretical distortion = 0.
Going back to the origin of NFB theory, we have adopted a linear feedback circuit that makes NFB work more ideally.
This circuit forms an independent feedback circuit that can provide infinite amplification in the NFB loop. It theoretically realizes an amplifier that performs ideal operation with theoretical distortion = 0, pure gain without influence of elements and power supply, and speaker drive without influence of back electromotive force and wire, further enhancing the quality of the new class A system.
This realizes low distortion and high sound quality.
It employs a new class A method using a synchronous bias circuit unique to Technics and eliminates switching distortion, which is the cause of sound nigori.
Switching distortion is caused by the asymmetry of the positive and negative waveforms near the 0 cross point of the signal when the output transistor is turned on/off in class B and class AB amplifiers. In order to solve this problem, the synchronous bias circuit applies a constant bias current to the output transistor and keeps it active at all times, thereby eliminating the switching distortion.
New Class A also eliminates crossover distortion, which is another cause of sound nigori.
Crossover distortion occurs when the positive and negative waveforms deviate from each other in the front-back direction of the time axis due to excess or deficiency of idling current, and when the rise and fall waveforms themselves do not have ideal squared characteristics and the positive and negative composite voltage characteristics do not become linear. In the new class A, the output transistor always keeps the appropriate operating point because the signal path and bias current are independent, and when combined with the function of the fast response diode with almost ideal squared characteristics, crossover distortion is also 0.
The phono equalizer is an ICL low-noise equalizer with the first stage FET differential amplification without the input capacitor.
The tone control circuit uses the NF loop of the main amplifier. A time constant element is inserted into the NF loop to form a tone control circuit.
In addition, the tone control is a center defeat type that ensures flat characteristics.
It is equipped with an electronic protection circuit to protect the amplifier and speaker from overcurrent.
Equipped with Route 3 AC outlet.
Model Rating
| Type | Integrated DC amplifier |
| Effective output (20 Hz to 20 kHz) | 30W + 30W (8 Ω, 0.007%) |
| Total harmonic distortion factor | 0.007% (Rated Output -3dB, 20 hz to 20 khz) |
| Output Bandwidth (THD 0.02%, 8 Ω) | 5 Hz to 50 kHz |
| Frequency characteristic | 20 Hz ~ 20 kHz + 0 -0.3 dB |
| Signal-to-noise ratio (IHF-A) | Phono MM:82dB Tuner, Tape, Aux : 98 dB |
| Residual noise | 0.5mV |
| Damping factor | 60 (8 Ω) |
| Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Tape, Tuner, Aux : 150mV/22k Ω |
| Phono maximum allowable input (1 kHz, RMS) | 130mV |
| Tone control | Bass : ± 10 dB (50 Hz) Treble : ± 10 dB (20 kHz) |
| Loudness control (VR-30dB) | +9dB(50Hz) |
| Pwer | 100 VAC, 50Hz/60Hz |
| Power consumption | 78W |
| External dimensions | Width 297x Height 74x Depth 230 mm |
| Weight | 4.5kg |