Technics SE-A1

Commentary

A⁺Stereo DC power amplifier that realizes low distortion and high power by class operation.

A developed by Technics⁺Class amplification system is adopted.
Class A amplifier has the advantage of sound quality because the straight line part of the amplifier element is used in the full cycle of the signal, so there is no switching distortion or crossover distortion in principle. However, it has the disadvantage that half of the peak current must always be supplied even when there is no signal, and it is inefficient as an amplifier circuit.
A adopted for SE-A1⁺In the class operation, the ground potential of the class A amplifier, which requires a constant current, is floated, and if necessary, a high voltage is supplied from a separate power amplifier in synchronization with the amplitude of the audio signal, thereby eliminating forced air-cooling fans while maintaining output.

The power supply section is equipped with a large-capacity toroidal transformer with low DC resistance, one on each of the left and right sides, and an electrolytic capacitor is A.⁺It is equipped with 4 100,000 μ Fx4 for class amplifier and 4 22,000 μ Fx4 for power amplifier. It is composed of 2 monaural with 4 power supplies per channel and total 8 power supplies.

A DC amplifier configuration that eliminates the input / output coupling capacitor and the capacitor in the NFB loop realizes excellent waveform transmission characteristics.
In addition, an active thermal servo amplifier is adopted as a countermeasure against DC drift. Since DC drift is suppressed by thermal feedback to the first stage through a separate path separated from the signal system, the DC gain of the signal system is always kept constant.

In consideration of the case where DC component enters the speaker, a protection circuit is mounted which separates the speaker terminal from the circuit when a relay is activated. In addition, when the speaker terminal is short-circuited due to misuse, etc., a current limiter is activated to protect the circuit. In addition, a current limiter is activated to protect the transistor against a temperature rise of the transistor due to a decrease in load impedance.

Equipped with a high-speed response peak meter that accurately indicates even an attack time of 50 μ sec / 20 khz single wave.
The scale is equally spaced logarithmic compression of + 10 dB ~ -50dB.

Equipped with four independent speaker output control switches (0 to -20dB) for level presetting.

Equipped with 4-step speaker impedance selection switch for meter.

Equipped with a fade-in / out mechanism without shock sound for transient generation at input ON/OFF or DC / low-cut switching.

The power ON / OFF of the power amplifier can be remotely controlled by the power ON / OFF of the preamplifier.

Model Rating

Type	Stereo DC power amplifier
Effective output (both channel drive)	350W + 350W (4 Ω, 20 Hz to 20 kHz) 350W + 350W (8 Ω, 20 Hz to 20 kHz)
Total harmonic distortion factor	0.003% (20 Hz to 20 kHz at rated output) Unmeasurable (at rated output, 1 khz) 0.01% (175 kHz at W, Rated Output -3dB)
Output bandwidth	5 Hz ~ 100 kHz (8 Ω, both channel drive, 0.01%)
Frequency characteristic	20 Hz ~ 20 kHz + 0 -0.05 dB DC ~ 200 khz + 0 -1dB
Signal-to-noise ratio (IHF-A)	120dB
Residual noise	500 μ V (150 μ V, IFF-A)
Damping factor	100 (8 Ω)
Slew rate	70 V / μ sec or more
Input Sensitivity / Impedance	1 V ~ 10 V (Continuously Variable) / 47k Ω
Load impedance	A or B or C or D : 4 Ω ~ 16 Ω A + B or B+ C or A + C : 8 Ω ~ 16 Ω A + B+ C : 16 Ω
Meter Characteristics
Indication range	-50dB to + 10 dB (Regular Interval Scale)
Frequency characteristics (indication accuracy)	10 Hz ~ 20 kHz ± 1 dB (+ 10 dB ~ -40dB Indication) 10 Hz to 10 kHz ± 3 dB (When less than -40dB is indicated)
Attack time	50 μ sec
Recovery time	750 msec (0 dB → -20dB)
<General>
Pwer	100 VAC, 50Hz/60Hz
Power consumption	1kW
External dimensions	Width 450x Height 249x Depth 550 mm
Weight	51kg