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 api 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.
The input impedance of the mic input mode can be switched between 1200
and 300 ohm. Phantom power and phase reverse is also selectable by front
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 2 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.
These two DI-options makes it possible to get different tones from
electric instruments and the passive DI input mode is more suited for
injecting active units like sound modules.
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 second Golden Age Project module for the api 500 rack will be the
EQ-573, expected to ship in November 2012. The EQ-573 consists of the
inductor based high pass filter section and the 3-band eq section from
the classic 1073 module with some added frequencies. These two modules
together will offer a fully fledged 1073-module in a compact format at a
very low cost.
There is a second jumper at the back of the module that selects 600 ohm
termination on the output. The standard mode is termination on, since
it gives the flattest response when the PRE-573 is used with modern line
inputs that typically has an input impedance of 10 kohm or more. The
user can chose to remove the jumper and deactivate the termination
resistor, this will increase the level above 10 kHz and create a peak in
the response for an even more pronounced “Air” effect.
The output is transformer balanced and fully floating and can drive a 600 ohm load up to level of about 28 dBu.