Accuphase PS-520 User Manual
●AC vo lt age s ta bi li ze r b as ed on w av ef orm s ha pi ng te ch no lo gy ●
plies up to 510 VA of extremely clean energy
generator
●Highly effective waveform compensation ●
capability
●Superb interference rejection ●
●Low-distortion reference waveform
Outstanding current
Built-in meter for monitoring vital
Sup-
pa ra me ter s: o ut put pow er , input /o utp ut v ol tag e, i np ut/ ou tp ut di st or tio n
●Sophisticated protection features ●
Large, high-efficiency toroidal transformer
The photograph shows the 230 V version.
Solve power supply problems once and for all — Revolutionary waveform
shaping technology made even more precise, to create a pure energy
source of up to 510 VA, rated for 120 V ±1.5 V/230 V ±3 V with max. 0.1%
THD. Connect audio or video equipment for a drastic improvement in
sound and picture quality. Visually monitor the quality and efficiency of
the power source using the built-in meter with AUTO-MONITOR function.
The Clean Power Supply components from Accuphase are
the result of intensive research into every aspect of powering
demanding equipment from the AC grid. They are designed to
ensure ideal conditions without compromise. Noise and
impurities are removed from the AC power line and signal
quality is improved by continually monitoring and shaping the
power supply waveform in real time. Revolutionary high-speed
circuitry adds or subtracts exactly the required amount of
compensation, thereby minimizing distortion and creating a
perfect waveform. The result is a drastic improvement in the
sound and picture quality of audio and video equipment.
The PS-520 features a differential push-pull arrangement of
power MOS-FETs for the waveform compensation amplifier,
which further improves the precision of the reference signal
and thereby the sound quality and performance of the power
supply. Balanced transmission is used for the link to the power
section, resulting in a cleaner output waveform with minimal
distortion. The use of high-quality AC outlets meeting exacting
standards with regard to electrical safety, and impedance
matching of all outlets means greatly improved reliability. All
circuitry in the PS-520 is analog. The power source waveform
containing noise and distortion is compared to a highly
accurate and stable reference waveform. Based on this
comparison, the PS-520 then adds or subtracts exactly the
required amount of correction to create a clean power supply.
The required compensation typically is only a fraction of
overall power, which allows the PS-520 to operate with high
efficiency while producing little heat. Since there are no
oscillators or switches, the PS-520 itself does not act as a
source of spurious high-frequency noise.
AC Voltage Stabilizer Based on Waveform Shaping Technology
The PS-520 accepts AC power on the input side, processes it with
internal control circuitry, and supplies it as clean AC power on the
output side. Most
of the AC energy
from the input is
carried over to the
Efficiency
[%]
Input power
[VA]
Load: purely resistive
Efficiency
output. The introduced loss consists
only of the power
Input/output power
required for waveform compensation.
As shown in Figure
1, the signal from
the secondary winding S
1
of the transformer reaches the
adding/subtracting
circuit and appears
at the output as
output voltage
e
0
. The secondary winding S
signal from the
transformer goes
0 100 200 300 400 500
Output power/input power (efficiency) characteristics
THD
[%]
0.8
0.6
0.4
0.2
0
2
Load: purely resistive
100 200 300 400 500
Output power/THD characteristics
PS-520 Load Characteristics
Output power [VA]
Output power [VA]
to the reference
waveform generating circuit where it becomes a high-precision sine
waveform ei synchronized to the input frequency of 50/60 Hz. This
reference sine wave e
i
is then used as reference signal to be compared to the output voltage. The differential component is extracted
and used by the adding/subtracting circuit to provide exactly the
required amount of compensation for turning the output into a highprecision waveform.
Superb Interference Rejection
The input side of the PS-520 is equipped with a line
filter, an isolation transformer with shielding between
The diagram shows the 230 V AC version
Measurement circuit transformer
Waveform
after filtering
protection
Inrush current
Isolation
transformer
Hum blocker
Before waveform shaping
Input waveform with
noise and distortion
〜AC IN
Circuit
protector
Line filter
Figure 1 PS-520 Operation Block Diagram
Before waveform shaping
S1
SecondaryPrimary
S2
Meter
Large filtering
capacitors
Rectifier
Balanced
transmission
signal
generator
Reference
Reference waveform
e
i
the primary and secondary side, and a high-speed
adding and subtracting circuit. This thorough,
three-stage approach reliably removes any
high-frequency noise components present in the
power line, such as generated by digital equipment.
The output impedance of the amplifier section is
extremely low, which minimizes the risk of mutual
interference between components connected to the
outputs of the PS-520.
Built-in Meter Allows Easy Monitoring of
Output Power (VA), Input/Output Voltage (V),
Input/Output Distortion (%). Excessive Load
Indicated by Flashing LEDs.
T
he constantly fluctuating voltage and distortion at a
regular household AC outlet can be monitored in real time.
Assembly with input voltage/distortion monitoring circuitry
The meter also lets the user see at a glance how much
power (VA) the connected equipment is consuming at any
given time, which is especially helpful for components
such as power amplifiers whose power consumption
differs considerably depending on the actual volume.
An AUTO-MONITOR function that automatically switches
the meter indication is also provided.
Power Supply Waveform and Clean PS-520 Output Waveform
Almost all electrical devices used in a household convert the AC supplied by the
outlet into a DC current for powering internal circuits. This task is performed by a
rectifier consisting of a combination of diodes and capacitors. The rectifier load
current has a pulse characteristic with a large current flowing momentarily in the
vicinity of the peak of the voltage waveform (sine waveform). The resistance of
electrical in-wall wiring and power cords affects the waveform and leads to a drop in
voltage, which is seen as clipped waveform with higher amounts of distortion. The
clipped waveform results in less power being available, so that connected equipment
does not receive enough energy to develop its full potential. The distorted waveform
also contains many unwanted frequency components, or harmonics. When entering
the audio circuitry of an amplifier through the power supply, such harmonic
components can interfere with the audio signal and cause intermodulation distortion
which has a highly detrimental effect on sound quality. The AC power therefore not
only is subject to noise and distortion while being delivered to the load, it is then
further degraded in the equipment itself through the process of power consumption.
When passing through the PS-520, practically all unwanted harmonics components
in the audible range are removed (see frequency spectrum in the graph below), and
the waveform is restored to its original sine wave pattern as shown in photograph (c).
−
−
〔dB〕
−
−
−
−
100.0
120.0
AC Line Power Spectrum 1
0.0
50Hz
20.0
40.0
60.0
80.0
0 10k 20k
Frequency spectrum of power line (photo b)
Frequency spectrum of power line
〔dB〕
PS-520 Output Power Spectrum 1
0.0
50Hz
−
20.0
−
40.0
−
60.0
−
80.0
−
100.0
−
120.0
〔Hz〕
0 10k 20k
Frequency spectrum of PS-520 output (photo c)
Protection
circuit
DC/AC detection
Temperature detection
Adding/
subtracting
circuit
Waveform
comparator
〔Hz〕
Function buttons and LED indicators
Meter switching circuit
Measurement circuit
Output waveform
e
o
OUTPUTS
Current detection
Error
detector
Reference waveform
Waveform
differential component
compensation amplifier
Meter scale of 230 V AC version
Waveform control circuit
Photo (a) Current waveform of rectified load
Photo (b) Voltage waveform of AC line
(distortion approx. 3%)
Photo(c)PS-520outputwaveform
(distortionapprox.0.06%)
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