The ML-9 is a basic
stereophonic amplifier with many of the features of the higher-powered ML-3.
the ML-9 is rated at 100 Watts continuous sinewave power per channel into 8
ohms, with both channels driven, from 20 Hz to 20 kHz with no more than 0.2%
Total Harmonic Distortion. It will drive even the most inefficient loudspeakers
to their full potential. In fact, the ML-9 will easily satisfy the power
requirements of all but the most unorthodox applications.
The design goal of
the ML-9 was to provide the same overall performance of the Ml-3 in a component
with about half the power, size and price.
Thus, the audio
circuitry of both models is similar. Push-pull operation is maintained from
input to output. Full protection is provided for both the amplifier and the
load. The power supply of the ML-9 consists of a 1,2 kVA toroidal transformer
and a pair of 36 milli-Farad capacitors, allowing for energy storage in excess
of 230 Joules.
The damping factor
can be adjusted by means of a three-position toggle switch on each channel to
meet the requirements of virtually all presently available loudspeakers. The
ML-9 has been designed to drive complex loads with complete stability.
Circuit description
The ML-9 is a high
quality Class AB₂ stereophonic amplifier designed to provide virtually the same
sonic performance as the ML-3 in a component of about half the power, weight,
size and price.
Power Supply
Consists of a 1,2
kVA toroidal transformer, a 30A bridge rectifer, and two 36,000 µF capacitors.
Four 520 µF capacitors are used for added decoupling of the pre-driver stage.
Pre-Driver Stage
Consists of a
differential amplifier with a cascode which drives a second differential
amplifier with a cascode and a current inverter. The inverter converts from
balanced to ground (differential) to unbalanced to ground while maintaining
push-pull operation.
Driver Stage
Consists of a
complimentary emitter follower, driving a second complimentary emitter
follower.
Output Stage
Consists of four
parallel complimentary push-pull emitter followers
Protection
The on/off switch
doubles as an electromagnetic circuit breaker to protect the amplifier from
excessive current. The power stages are protected by an energy limiting circuit
which monitors power dissipation versus time. Independent energy limiting for
positive and negative information minimizes distortion while in the overload
condition. This circuit offers excellent protection without effecting the sonic
quality. The loudspeaker is protected by a D.C. sensing circuit that monitors
the output of the amplifier. The D.C. sensing circuit is connected to the
circuit breaker. Several other techniques have been employed to protect the
ML-9 from external sources of damage.
Selectable damping
Factor
Loudspeakers, like
all electrical devices, are not perfect. We have determined that certain
loudspeaker characteristics can be effected by varying the damping factor of
the amplifier. For the reason the ML-9 is equipped with selectable damping
capability.
Specifications
Rated Power: 100 watts continuous sine-wave power pre
channel into 8 Ω with both channels driven from 20 Hz - 20 kHz with no more
than ,2% T.H.D.
Frequency
Response: (-3 dB) 3 Hz, 44 kHz (ultra
sonic filter is a modified bessel alignment)
Input
Impedance: 50 k Ω
Voltage Gain: 26 dB
Power
Consumption: 400 W at rated output into
8 Ω, 50 Hz - 400 Hz (100 W at idle)
Overall Dimensions
(W x H x D): 482 x 216 x 339 mm (19" x 8-1/2" x 13-3/8")
Weight: 29,48 kg (65 lbs)
Connector
Complement: 2 Camac coaxial connectors;
4 binding posts
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