Technics SEA 5 Owners Manual

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chhnics

Stereo DC Power Amplifier

SE-AS

OPERATING INSTRUCTIONS

Before operating this urni. please read mesa instructions compiekely.

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tion to say that this technology marks significant progress
toward maximizing the A value (open loop gain) while mini-
mizing the values of 2.. (output impedance without N.F.B.) and
Du (distortion without N.F.B.) in order to improve the perfor-
mance of a conventional negative feedback amplifier. Untiring
research and effort continue at Technics in order to improve the
basic characteristics of the amplifier, with the goal of increasing
its performance capabilities.

This amplifier represents an ideal in this search. the realization
of a dream long held by researchers: success in attaining infinite
open loop gain (A = DC), the ideal condition for the negative
feedback amplifier, with no deterioration of the phase charac-
teristic in the high frequency range.

When the condition A = x is applied to each factor of the
negative feedback amplifier, the degree of amplification (gain)
after negative feedback becomes 1/13, making the feedback
factor (constant resistance value) the only determining
element.

Virtually all conventional amplifier problems, such as active-
element distortion, noise. influencefrom the power source. etc.,
can be disregarded, and the operation of a truly ideal negative
feedback amplifier can be appreciated.

The same can be said regarding distortion; the level of distortion
after negative feedback is zero. and the performance of the
amplifier is greatly improved.

Another remarkable achievement is the fact that the output
impedance reaches the theoretical value of zero.

In other words. the damping factor as it approaches infinity,
ideally. makes it a possibility to continue driving a set of speaker
systems.

The performance capability exists to completely eliminate
distortion caused by a reverse flow of electricity generated by
the speaker systems (induced intermodulation).

I Concentrated Power Block minimizes distortion
caused by electromagnetic induction.

Electromagnetic radiation from components'dealing with heavy
current such as the output stage and the power supply is a great
enemy when it comes to reducing distortion. This is because
electromagnetic waves, similar to the signal frequency,
emanating from wiring carrying a heavy current. affect parts
carrying a light current load, thus aggravating interference
distortion.

Worse still is the phenomenon that the emanated electromag-
netic waves. after passing through such magnetic bodies as the
metal chassis. enter the signal system.

Technics has long been concerned with this phenomenon, but,
rather than just trying to reduce the effect of electromagnetic
waves after they appear. Technics was looking for a way to
prevent these electromagnetic waves from forming in the first
place. by establishing a concentrated powerblock" technique
which is used in this unit.

Our aim is toward perfection in shielding the equipment from
both static electricity and electromagnetism, and. from this
point of view, the Concentrated Power Block plays an important
role.

I A full/limited output power switching circuit for
energy saving" option.
A unique feature of this unit is the output power selector. There
is a choice between the "full" position, which gives a tremen-
dous power output of 120W + 120W (80), and the "limited"
position, giving 30W + 30W (80) output.
If the limited" position is selected, the large power supply of the
120W amplifier provides 30 watts of sound with plenty to spare.
permitting enjoyment of luxurious sound for quiet surroundings
at night. for example. and saving energy too.
Furthermore. when the switch is set to the limited" position. the
meter illuminations are also turned off. and powerconsumption
when there is no signal is reduced to 33 watts. Of course, when
you want to experience the excitement of the full power. you can
do so by simply setting the switch to the full position.

I Protective circuit operated by automatic return
relay equipped with indicator

In a high-power DC amplifier of this type, it is necessary to give
Sufficient consideration to protection circuits for the speakers
and the amplifier itself.

The protection circuit of this unit is such that. if by any chance
DC Output appears at the speaker terminals. a relay operates to
protect the speakers, and. moreover. in the event of a short-
circuit at the speaker terminals. the relay operates to protect the
amplifier.

When the cause has been eliminated. the relay automatically
returns to normal.

I Other features

0 Large VU-type power meters.
Without switching the range. direct readout from a low
output of 0.0001W (0.1 mW) to 300W is possible.

0 Power transformer featuring low vibration and low leakage
flux resin seal.
The transformers lack of hum is one excellent indication of
the amplifier's quality.

a High signal-to-noise ratio of 108 dB (123 dB. lHF. A).
This low level of residual noise deserves special mention.

0 Current-surge prevention.
This is a special circuit to prevent the surge of peak current
that may occur for a few seconds after the power is switched
on. There is none of the dimming of electric lights that
sometimes occurs after a high-power amplifier is switched
on.
Easy-to-connect speaker terminals.
Attractively styled diecast panel.
Gold-plated input terminals and shielded plugs: further
examples of our efforts to ensure long and useful service
from this unit.