Golden Age Project | Pre-573 MkII

The PRE-573 MkII 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 MkII 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. 

*Please Note: The PRE-573 MkII draws quite a high current at power on. This is the reason it wont work in some racks that uses a switched power supply. We have had several reports about problems when trying to use the PRE-573 MkII in the Radial racks. Racks using a linear power supply, like the racks from api audio, works well, we have not had any reports on problems in these cases.

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