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Golden Age Project
Pre-573 MKIII (500 series) 1073 style Microphone Pre-Amplifier
The
PRE-573 is a one width module that has the sound and the features that
made the PRE-73 so successful and a few additional ones.
The
circuit still uses the preamp and output section from the classic
1073-module, adapted to work in the 500 series rack format. It has a total
gain range from -15 to +80 dB. The 10 – 70 dB range is handled by a turn
switch and there is a separate toggle switch to select an additional 5 or
10 dB gain. The input can be configured to accept line level signals by
another switch, the gain is then lowered by about 25 dB and the input
impedance increased to about 15 kohm.
An
added feature, using the same circuit as in the PRE-73 DLX, is the active
DI-input with a high input impedance of about 1,5 Mohm. The output signal
from the active DI circuit passes through the input transformer for some
extra character.
The
DI-input is very flexible since it can be changed to a purely passive one
by a front panel switch. The DI input is then exactly the same as in the
PRE-73 Mk2 where the signal is feed directly into the second gain stage,
bypassing the transformer and with an input impedance of about 100 kohm.
A
new feature is the switchable AIR mode that adds a small boost above 10
kHz that peaks at 2 dB at about 35 kHz.
A
simple but effective signal and overload indicator is offered by a single
LED that starts glowing red at about +4 dBu and then increases its
intensity up to the maximum output level.
The
PRE-573 has a dedicated insert connector at the back allowing it to
interface with other GAP 500 modules. The insert can be activated by
removing a jumper connector at the back of the module.
The MKIII version has the addition of a
2-position high pass filter.
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