The Golden Age Music PRE-573 MKII Plus 500 Series 1073-Style Microphone Preamp brings the classic 1073 sound to a 500 series lunchbox-style form factor. The "Plus" version of the microphone preamplifier uses Carnhill transformers for the input and output stages of the signal.
The unit is one lunchbox space wide and features a total gain range from -15 to +80 dB. The 10 to 70 dB range is handled by a turn switch, and a separate toggle switch allows you to select an additional 5 or 10 dB of gain. The input can be configured to accept line-level signals by another switch. The gain can be lowered by about 25 dB and the input impedance can be increased to approximately 15 kOhms.
The input impedance of the microphone input mode can be switched between 1200 and 300 ohms. Both phantom power and phase reverse are provided by selectable front-panel switches. An active DI input can be engaged with a high input impedance of about 1.5 MOhms. The output signal from the active DI circuit passes through the input transformer for extra character. The DI input can be changed to a purely passive input by a front-panel switch.
The two DI options make it possible to achieve different tones from electric instruments, and the passive DI input mode is more suitable for injecting active units like sound modules. A switchable AIR mode can be engaged to add a small boost above 10 kHz that peaks at 2 dB around 35 kHz.
A single LED serves as both a signal and overload indicator that starts glowing red at about +4 dBu and increases with intensity up to the maximum output level. A dedicated insert connector at the back of the unit allows it to interface with other GAP 500 modules. The insert can be activated by removing a jumper connector at the back of the module.
A second jumper at the back of the module selects 600 ohm termination at the output. The standard mode is termination on, since it gives the flattest response when the unit is used with modern line inputs that typically have an input impedance of 10 kOhms or more. The user can chose to remove the jumper and deactivate the termination resistor, which will increase the level above 10 kHz and create a peak in the response for an even more pronounced "Air" effect. The fully floating balanced output transformer can drive a 600 ohm load up to a level of about 28 dBu.