This microphone preamplifier is housed in a 1U rack mount chassis. It is a two channel mic preamp with individual controls for each channel.
Front panel controls include: Mute switch (mutes output), polarity reverse switch (relay), phantom power, 24 position rotary gain switch, and dual color LED signal level indicator (green @ -5 dBu, Red @ +22 dBu).
There are two inputs per channel. One has +48 volt phantom power supplied to it (when phantom power is switched on) and its signal passes through very high quality capacitors to block the phantom power DC voltage from the input stage of the preamplifier. The other input is connected directly to the input of the preamplifier, bypassing the phantom power blocking capacitors. You can use this “direct coupled” input when you are using a microphone that does not require phantom power, such as vacuum tube mics, ribbon mics, and dynamic mics. You can only use one of these inputs at a time. Do not connect anything to the unused input. Input and Output connectors are XLR-3 wired pin #2 hot.
The front panel mounted bicolor LED will light green when an output signal level of –5 dBu or greater is present, and this LED will turn red when the output signal level reaches +22 dBu. This is approximately 3-4 dB before output clipping on the 2 channel preamp.
Circuit description
Class A discrete JFET front-end and opamps (3). IC servo amp (DC offset control) on output. All DC coupled EXCEPT for phantom powered inputs. 48 VDC full current power supply. +/- 24 VDC power supply rails.