Mono 500 Series 1073 Vintage Style Microphone Preamplifier

The PRE-573 MKIII is a one width module for the api 500 format 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 -10 to +80 dB. The 20 – 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 30 dB and the input impedance increased to about 10 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 panel switches. 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 MKIII 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 boost above 10 kHz that peaks at 6 dB around 30 kHz. The MKIII version has two position high pass filter as an added feature. 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 MKIII has a dedicated insert connector at the back allowing it to interface with other GAP