||453,000yen(around the 1980 time)
Stereo power amplifier carrying a power guarding
system original with a mac.
It is MC2125 with the identical configuration
mostly except the power meter.
If an output wave is electrically
compared with an input wave and the wave difference becomes 0.5%, a Limit lamp
will light up and a Normal lamp will go out in the circuitry which realized the
power guarding system by the wave comparator of the mac original design.
Moreover, if a wave difference reaches to 1%, the power guarding circuitry
operates, it will prevent amplifier carrying out clipping, and distortion will
not be reproduced from a speaker, but a speaker will be protected
An input wave and an output wave are compared by IC
differential amplifier, and the wave difference by distortion of an output wave
is changed into a voltage. Moreover, this voltage is amplified about 100 times
and supplied to a Schmidt trigger circuit through a full wave rectifier circuit.
Moreover, this voltage uses a power guarding circuitry, and if it becomes higher
than the level which a voltage makes turn on a Limit lamp, it will operate a
power guarding circuitry.
The Limit lamp is designed switch on the light also when amplifier overloads,
and even if overload status is very short, it is turned on between the
grades which can be viewed. In this case, meter displays 200W cuttlefish.
To use a power guarding circuitry, it is necessary to set
the power guarding switchpoint of a rear surface panel to Normal. Even if this
switchpoint is in the location of out, only the Limit lamp operates.
output signal of amplifier is supplied to an output-terminal through an output
transformer. This transformer is designed match sy copy power termination of
every impedance, and even if it uses which output-terminal, the maximum output
is obtained to all the signalling frequencies.
Moreover, a transformer
eliminates that component and this transformer prevents a corruption of a
speaker, when it also has the role which protects a speaker in the case of a
malfunction of amplifier, for example, a direct current component mixes in an
In order to prevent an output transistor overloading, the output
signal is always supervised in the monitor circuitry. This circuitry will become a high impedance if an Output voltage becomes more than a rate. When an output
becomes a upper, the signal supplied to an output transistor by the monitor
circuitry is restricted, and prevents a corruption of an output transistor.
Distortion is removed using the monolithic transistor differential
amplifier with few noises to the input side of a power amplifier part. An input
signal and a feedback signal are supplied to this differential amplifier. The
circuitry of the following stage is a voltage amplifying circuit which operates
with a Class-A. A driver circuitry and an output circuit adopt a complimentary
scheme, carry out the operation near a Class-A, and lessen crossover distortion.
To the transition of a temperature, this circuitry is designed so that a
moderate bias may always start.
The power transistor serves as AB class operation, and, as for the bias
current, the safeness is maintained with the thermistor. The output circuit
has adopted the para-push scheme of a single ended. It consists of six
reliable complimentary power transistors. Since this circuitry is an equilibrium
nature Emitter-Follower join, a stability is good, and distortion's has
decreased and B class operation without crossover distortion is carried
out by adoption of the still more original output bias circuitry.
||Stereo power amplifier
15.5Vrms (at the time of a
2-ohm load intensity)
21.9Vrms (at the time of a 4-ohm load intensity)
31.0Vrms (at the time of an 8-ohm load intensity)
43.8Vrms (at the time
of a 16-ohm load intensity)
15.5Vrms (at the time of a 1-ohm
21.9Vrms (at the time of a 2-ohm load intensity)
31.0Vrms (at the time of a 4-ohm load intensity)
43.8Vrms (at the time
of an 8-ohm load intensity)
|Output load impedance
||stereo: 2 ohms, 4ohm, 8ohm, 16ohm
1 ohm, 2ohm, 4ohm, 8ohm
||20Hz - 20kHz
||0.1% or less (at the time of Outputs
0.25W-120W, 20Hz - 20kHz, and both ch(es) operation)
|Cross modulation distortion
||0.1% or less (at the time of an Output
(at the time of 1W output)
|20Hz-20kHz+0 -0.25 dB
||95dB or more (at the time of an Output
||stereo: 16 (2ohm), 50 (4ohm), 20 (8ohm), 14 (16ohm)
mono: 16 (1ohm), 50 (2ohm), 20 (4ohm), 14 (8ohm)
||0.75V, 2.5V (switching type) / 100kohm
|The semiconductor used
||Silicon transistor: 39 pieces
Silicon diode: 24 pieces
||50W (at the time of a non-signal)
(at the time of a maximum rating output)
||Main unit: Width 372x height 127x depth of
Front panel: Width 407x132mm in height
31.8kg (at the time of an