file Technics SE-A1 Power Amplifier (1977)

09 Feb 2016 17:57 - 09 Feb 2016 18:20 #1 by Trony
Trony created the topic: Technics SE-A1 Power Amplifier (1977)

Stereo DC power amplifier which realized a low distortion and high power by A+ class operation.

A+ class amplification scheme which technics developed has adopted.
Since Class-A amplifier is using the linear-line fraction of an amplification element in the full cycle of a signal, neither switching distortion nor crossover distortion exists theoretically, but there is a tone-quality merit. However, it is necessary to always send the electric current of the one-half of the peak current also at the time of a non-signal, and has the fault that it is inefficient as an amplifying circuit.
In A+ class operation adopted as SE-A1, the floating of the grounding potential of the Class-A amplifier which always needs an electric current is carried out, and the high voltage is supplied from the power-source amplifier formed separately if needed synchronizing with the swing of an audio signal. it is a twist in this -- the forced-air-cooling fan is eliminated, securing an output.

The mass toroidal transformer with little direct current resistance is carried in the power-source part every one right and left each. Moreover, A+ class amplifier is equipped with the electrolytic capacitor 22,000 micro Fx4 100,000micro-Fx4 and for power-source amplifier, and it has 2 monophonic composition of four power sources and a total of eight power sources per channel.

DC amplifier stream composition which banished the coupling capacitor of an input and an output and the capacitor in a NFB loop is adopted, and the outstanding waveform-transmission property is realized.
Moreover, active thermal servo amplifier is adopted as the measure against DC drift, and since another path by which the suppression of DC drift was separated from the signal system is performing by the thermal feedback to the first rank, DC gain of a signal system is always kept constant.

In consideration of the case where DC component goes into a speaker, the protection network which a relay works and separates a circuitry from a speaker termination is carried. Furthermore, when a speaker termination short-circuits by misuse etc., a current limiter works and a circuitry is protected. Moreover, a current limiter works also to the temperature rise of the transistor due to the fall of a load impedance, and a transistor is protected.

The peek meter of the high-speed response correctly directed also by attack-time 50microsec and 20kHz1 wave is carried.
The tick mark serves as a regular-intervals logarithmic comression window of +10dB--50dB.

The speaker output control switchpoint (0--20dB) with four independent lines in which level presetting is possible is carried.

4 step speaker impedance change-over switch for meter is carried.

Fade-in / out organization without shocking sound are carried to the transient occurrence at the time of input ON/OFF, and DC / low cut switching.

By power-source ON-OFF of a preamplifier, power-source ON-OFF of power amplifier can be operated by remote control.

Rating of a mode
Stereo DC power amplifier
Effective output (both channel drive):
350W+350W (4 ohms, 20Hz - 20kHz) | 350W+350W (8 ohms, 20Hz - 20kHz)
0.003% (at the time of an Output power 20Hz - 20kHz)
Incapable measurement (at the time of an Output power 1kHz)
0.01% (175W, Output-power-3dB o'clock, 100kHz)
Output bandwidth:
5Hz - 100kHz (8 ohms, both channel drive, 0.01%)
Frequency characteristic:
20Hz-20kHz+0 -0.05 dB
DC-200kHz+0 -1dB
SN ratio:
(IHF-A) 120dB
Remains noise:
500 microvolts (150 microvolts, IHF-A)
Dumping factor:
100 (8ohms)
Slew rate:
More than 70v/microsec
Input sensitivity/impedance:
1V - 10V (succession variable) / 47kohm
Load impedance:
A or B or C or D : 4ohms - 16ohms
A+B or B+C or A+C: 8ohm-16ohm
A+B+C: 16ohm

<Meter property>
Indicating range:
- 50dB - +10dB (regular-intervals tick mark)
Frequency characteristic (indication precision):
10Hz-20kHz±1dB (at the time of +10dB - -40dB indication)
10Hz-10kHz±3dB (at the time of a less than -40dB indication)
Attack time:
Recovery time:
750msec (0dB->-20dB)

Power source:
AC100V, 50Hz/60Hz
Power consumption:
Width 450x height 249x depth of 550mm

Music and Electronic Devices Designer. Drum and Bass Addict. Creative Mind as Lifestyle. Cat in past Life. Soccer, Ice Hockey and Snowboard Lover. Marxist.
Sono Il Re sul Carro Danzante. Attraversando La Città Getto Via I Coriandoli Della Vostra Tristezza Regalando Passione Ed Estasi Nei Vostri Occhi.
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Last Edit: 09 Feb 2016 18:20 by Trony.

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