Great River MP-500NV, I/O connections: XLR balanced; high-Z input on front panel (disconnects mic input), Adjustable gain stages: input in 5db steps to 60db; output from -25 to +10db; maximum overall gain 70db; 2 to 3 stages of single ended solid state amplifier gain blocks, depending on gain structure; high-current 70ma Class A bias on output stage, Input and output meters on each channel (dual-stage metering is a Great River exclusive), Front panel switches: polarity; phantom power; input impedance (1200 / 300 ohm); output loading (600 ohm resistor across output transformer), High quality, custom wound Sowter transformers, Gold plated switching contacts, Format: API Series 500, Mounts in 2 spaces in a "500" rack