Technics SU-V8
¥ 99,800 (released in December 1979)
Commentary
Integrated DC amplifier using Technics original new class A system.
It employs a new class A amplification method using a synchronous bias circuit unique to Technics and eliminates switching distortion, which is the cause of sound turbidity.
Switching distortion occurs in class B and class AB amplifiers because the positive and negative waveforms become symmetrical near the 0 cross point of the signal due to the accumulation effect of carriers when the output transistor is turned on/off. In a synchronous bias circuit, a constant bias is applied to the output stage so that the output stage is always active and the switching distortion is 0.
In the new class A, crossover distortion is also eliminated.
The crossover distortion is caused by a time lag between the positive and negative waveforms due to excess or deficiency of idling current, and the waveform itself does not have an ideal square characteristic and the combined positive and negative transfer characteristic does not become a straight line. In the new class A, the signal path and bias current are independent, so the output transistor always keeps an appropriate operating point, and the high-speed response diode that switches between the positive and negative waveforms has almost ideal square characteristic, so the crossover distortion is 0.
A straight DC system is adopted in which a high gain input is directly connected to a high gain DC power amplifier to obtain faithful amplitude and phase frequency characteristics up to the DC region.
In addition, the first stage differential amplifier circuit of the power amplifier is composed of one chip dual FET, and DC drift is suppressed to ± 10 mv or less in the range of -10 ℃ to + 50 ℃. In addition, NFB is suppressed to 45 dB by adopting a circuit configuration that greatly improves bare characteristics such as linear cascode circuit and 3-stage Darlington circuit.
The phono equalizer employs a low-noise dual-FET differential amplifier at the first stage. Both MM and MC are ICL equalizers with an input capacitor attached to them, realizing a low-noise, high-gain MC basic design.
It uses a concentrated power block, and by integrating the power supply and output transistor and connecting them at the shortest distance, high-frequency distortion caused by electromagnetic waves is minimized.
The power supply section has two completely independent power supply configurations with separate power transformers for the left and right channels, eliminating transient crosstalk through the power supply section.
In addition, a constant voltage load by FET is adopted for the error detection circuit load of the constant voltage power supply. By stably supplying a constant voltage with a high ripple removal rate to the voltage amplification stage up to the first stage of the main amplifier, self-transient crosstalk is prevented.
The power transformer has a structure in which the coil is floated in special resin and stored in a shield case. This realizes a lorry cage and a high SN ratio (minimizing mechanical vibration of the transformer).
Equipped with a Super Base Tone Control that allows you to expand the speaker frequency and characteristics by up to one octave into the lower range with shelving tone.
This Super Bass can be used not only to correct the frequency characteristics in the ultra-low range of the speakers, but also to eliminate the low-range booming that is caused by the acoustic characteristics of the listening room. When the reverberation time is long, the room will sound uncomfortably at a specific frequency in the low range. With the Super Bass on, the normal bass tone control can be used to attenuate only the boomy frequency range.
The tone control is a type that is deviated at the midpoint.
Equipped with an automatic recovery type protection circuit that disconnects the speaker by activating a relay when a DC component appears on the speaker terminal or when the speaker terminal is short-circuited.
Model Rating
| Type | Integrated DC amplifier |
| <Overall characteristics of Tuner, Aux → SP out> | |
| Effective output (20 Hz to 20 kHz) | 110W + 110W (8 Ω, 0.007%) |
| Total harmonic distortion factor | 0.003% (Rated Output -3dB, 20 hz to 20 khz) |
| Power Bandwidth (THD 0.02%) | 5 Hz to 100 kHz |
| Frequency Response (Straight DC) | DC ~ 20 khz + 0 -0.1 db DC ~ 150 khz + 0 -3dB |
| TIM | Unmeasurable |
| SN ratio (IHF-A, straight DC) | 106dB |
| Residual Noise (straight DC) | 550 μ V |
| Damping factor (8 Ω) | 60 |
| Load impedance | Main or remote : 4 Ω ~ 16 Ω Main and remote : 8 Ω ~ 16 Ω |
| <Other characteristics> | |
| Input Sensitivity / Impedance | Phono MM : 2.5mV/47k Ω Phono MC : 170 μ V/47 Ω Tuner, Aux, Tape : 150mV/47k Ω |
| Phono SN ratio | MM:88dB MC : 71 dB (250 μ V Input) |
| Phono frequency characteristics | 20 Hz to 20 kHz, RIAA ± 0.2 dB |
| Shelving tone | Bass : ± 7 dB (100 Hz) Treble : ± 10 dB (20 kHz) Super bass : + 12 db (30 hz, 12dB/oct) |
| Turnover frequency | Bass:500Hz Treble:2kHz Super bass : 75 Hz, 150 Hz (12dB/oct) |
| Filter | High : 7 kHz, -6dB/oct. Subsonic : 20 Hz, -12dB/oct. |
| Loudness control | + 7 dB (50 Hz, Volume -30dB) |
| Muting | -20dB |
| <General> | |
| Pwer | 100 VAC, 50Hz/60Hz |
| Power consumption | 260W |
| External dimensions | Width 430x Height 153x Depth 351 mm |
| Weight | 15.7kg |