Golden Age Project PRE-573 MKII Mikrofonin esivahvistin

Rack version of the GAP PRE-73 MKII, single-channel low-cost vintage style microphone preamplifier with some additional features that is using a fully discrete signal path. The circuit still uses the preamp and output section from the classic Neve 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 microphone 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 model, 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. 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 also the switchable AIR mode that adds a boost above 10 kHz that peaks at 6 dB around 30 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. There is a second jumper at the back of the module that selects 600 ohm termination on the output. The preamplifier is equipped with a soft start circuit that ramps up the supply voltage slowly (about 10 sec.) to avoid a power-on current surge.