Sound Performance Lab EQ MAGIX - Manual (Page 10)

10
Special attention has been paid to the power supply of the EQ MAGIX.
The power pack is the heart of any unit, and the more accurately it works,
the more this improves results.
The power supply is installed around a toroidal-core transformer which
does not cause any electronic humming or mechanical sounds as a result of
its minimum leakage field. The primary voltage can be switched between
230 V / 50 Hz and 115 V / 60 Hz.
A 3-pole standard IEC mains connection socket serves to connect a
detachable 3-pole mains lead which is included in the scope of supply.
Transformer, power cable and mains connector comply with the require-
ments of VDE, UL and CSA. The fuse rating is 200 mA.
The connection between ground and housing can be separated via the
G ND L IFT switching option. Hum loops can be remedied in this way. Eloxal
has been removed from the back of the »ears« which serve to attach the
unit in a 19" rack, in order to achieve 100% contact to the rack rail, in case
the rack rail is used as a central ground. If the mains ground is inadequate,
an alternative connection for the ground can be obtained via the binding
post after activating the G ND L IFT switch.
On the secondary side of the power supply, an RC combination is used to
filter out noise and hum voltages from the mains side. Both half-waves are
smoothed with 4700
µF capacitors in the positive and negative voltage
path. Both pathes are calibrated separately via trimmers, as deviations of
only a few millivolts can result in audible changes such as a diffuse sound
pattern. After the calibration stage, the current is again smoothed.
Service voltage is raised gradually when the unit is switched on. This
prevents voltage peaks (e.g. switch-on cracks) affecting the operational
amplifiers. This safety circuit in turn prolongs the service life of the unit.
Safety diodes also ensure that the power pack is not damaged if there is a
short circuit within an IC.
An independent, self-contained power pack is used for the phantom
power supply. It obtains unregulated AC voltage from 2 x 25 V coils in the
transformer. This results in +/- 22.5 V DC via bridge rectifiers which are
filtered with 1000
µF. The DC voltage is adjusted to exactly 48 V in the
switching power supply (LM 311) downstream. It is then smoothed again
and stabilized. The power supply current flows to the intrusion point via
the PCB. An RC combination stabilizes the power supply again at this point.
Two medicinal 6.81 k
Ω resistors with a tolerance of only 0.1% are used as
bridging resistors.
A stable and well-filtered toro-
idal-core power supply provides
the basis for good sound proces-
sing.
The GND Lift switching option
helps remedy hum loops.
A binding post permits connection
of an alternative circuit ground.
Ample filtering, smoothings and
calibrations make for stable,
constant service voltage.
Protective circuitry prevents
premature aging or damage to
components.
The phantom supply voltage is
from a separate power supply
with sophisticated filtering and
selected components.
Power supply