Introducing
the Pure Zero Distortion Rule Sound
Her, at last, ia a power amplifier output stage that
actually adds no distortion to the music signal. Although the actual technology
involved in the Zero Distortion Rule amplifier is quite sophisticated, the
basic principle of this incredible high-accuracy amplifier is quite simple.
Essentially the Zero Distortion Rule system consists of a distortion detector
and a summer. The distortion detector derives a signal corresponding to any
distortion products originating in the amplifier itself, and the summer adds
this signal back into the original audio/distortion signal - out of phase with
the original signal. This effectively
cancels the distortion signal, leaving the audio signal intact and
virtually distortion-free. Of course, this system has no effect on distortion
originating in the source signal, only on distortion generated within the power
amplifier itself. From the above description we can see that if the derived
out-of-phase distortion signal were somehoe made larger than the original
distotion signal, summing these signals would actually result in a negative
distortion product. With this ingenious system, it has become possible to
produce a power output stage that actually exhibits no inherent distortion.
The Yamaha
Zero Distortion Rule Amplifier vs. Negative Feedback and Feed Forward Systems
Negative
feedback is the most commonly used means for reducing distortion in audio
amplifiers. The amount of distortion reduction, however , is directly
controlled by the amount of feedback applied. This means that in order to
reduce distortion to zero, infinite feedback must be appliedd. Obviously, it is
physically impossible to create infinite negative feedback, and therefore also
impossible to achieve zero distortion by this method,. Increasing application
of negative feedback can only approach the zero distortion ideal, while ZDR
actually permits crossing the zero distortion line and creating negative
distortion, making it theoretically possible to completely eliminate
distortion.
The feed
forward system of distortion reduction attemps to cancel distortion by adding
an inverted distortion signal to the audio signal to the audio signal at the
amplifier's output where signal power levels are high.
This means
that expensive, high-power feed forward circuitry is required, and overall
power efficiency is extremely low. Also,
the high-power feed forward amplifier required can actually add unwanted
distortion. Zero Distortion Rule performs its distortion cancellation ata the
amplifier's inputs thereby eliminating the power problem. And since the ZDR
circuit is essentially concerned only with low-level signal, it cannot add any
distortion of its own.
Linear
Transfer Bias Circuit
Another
feature of the M-50 power stage is its Linear Transfer Bias circuitry. This
unique bias syatem minimizes crossover distortion due to non-uniform linearity
between the power transistors in a push-pull power stage. By applying precisely
calibrated bias to each transitor in the M-50's cascoded push-pull power
circuit and thereby staggering the operating point of each, a perfectly linear
composite transfer characteristic is achieved, ensuring negligible crossover
distortion levels. The unbeatable combination of the Linear Transfer Bias
circuit and Zero Distortion Rule amplifier design results in outstanding
low-distortion power performance and incredibly natural source reproduction.
"X"
Power Purity
The concept
of "pure power" is extremaly important in achieving the highest power
amplifier performance. That is, the power source that supplies power to the
actual power amplification circuitry must by capable of providing extremely stable power, and at
the same time supply as much power as the amplifier circuitry demands without
"running out".
The Yamaha
"X" power supply easily meets the above requirements, with greater
efficiency and power capacity than aby other power system of its size or
weight. In principle, the "X" power supply controls the amount of
power fed from the AC line to the power
supply to precisely match the amount of power consumed by the amplifier
at any given instant. Whether the amplifier requires only a small amount of
power for average music levels, or a large amount for high-level music levels,
or a large amount for high-level music peaks, the "X" power supply
feeds precisely the required amount of power to the amplifier circuitry.
Naturally, this means that all the supplied power is consumed achieving
remarkable power efficiency.
In terms of
stability, the "X" power supply affords exceptionally high regulation
capabilities. Line supply voltage variations of as much as ±10% have no effect
on the "X" power supply's output voltage, and resistance to influence
by load variations is similarly high. The "X" power supply system
permits the amplifier circuitry to operate at optimum efficiency under optimum
conditions at all times, ensuring that the music source is reproduced with
maximum accuracy.
Speaker
Level Controls
In addition
to a speaker A/B selector that permits one-touch selection of two sets of
stereo speakers, the M-50 features speaker A and B level controls. These
controls let you independently set the maximum power level that will be sent to
the respective pair of speakers, protecting low-power-capacity speakers from
excessive power levels, or matching the output level of two sets of speakers of
different efficiency.
20-LED Peak
Power Output Meters
These
bright, attractive power meters let you see at a glance just how much power is
actually being fed to ypur speakers. This makes it easier to determine the
proper setting of the speaker level controls to prevent speaker breakup
distortion or burnout due to power levels exceeding the speakers capacity.
Specifications
Minimum RMS
Output per Channel:
120
Watts (8Ω, 20 to 20,000 Hz no more
than 0,002% THD)
200
Watts (4Ω, at 1 kHz, clipping Power)
Power
bandwidth (8Ω, Half rated
power): 10 to 100,000 Hz (0,02% THD)
Input
Sensitivity/Impedence (8Ω, rated
power): 1,1 V/25 kΩ
Frequency
Response (8Ω Half rated power, 100
kHz): -0,5 dB
Signal-to-Noise
Ratio (IHF A network): 122 dB
Total
Harmonic Distortion (8Ω Half rated
power):
20 Hz :
0,0005%
1 kHz :
0,0005%
20 kHz :
0,001%
50 kHz :
0,004%
100 kHz :
0,01%
Intermodulation
Distortion (8Ω Half rated power 50 Hz
: 7 kHz = 4;1): 0,002%
Channel
Separation (8Ω Half rated power ,
Input Shorted):
20 Hz : 100
dB
1 kHz ; 95
dB
20 kHz : 70
dB
Damping
Factor (8Ω 1 kHz): Better than 200
Slew Rate
(Sp Out): 200 V/µsec
Power
Supply: Matched to supply voltage and
frequency of all area
Power
Consumption:
USA and
Canada : 350 W/1,200 VA
Europe and
Australia : 550 W
Other Areas
: 200 W
Dimensions
(W x H x D): 435 x 133 x 380 mm
(17-1/8" x 5-¼" x
15")
Weight: 11,8 kg (26 lbs)
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