Focusrite ISA 428 MkII Four-Channel Microphone Preamp

ISA 428 MkII is the four-channel ISA preamp: four transformer-coupled microphone channels, four front-panel instrument inputs and four line inputs in a 2U enclosure with everything on the front where a session can reach it. Gain runs 0 to 60 dB in 10 dB steps with a continuously variable 0 to 20 dB trim, for 80 dB in total.

Impedance is switchable per channel between 600, 1400, 2400 and 6400 ohms; the 1400 ohm setting is the original ISA 110 load. A continuously variable high-pass filter sweeps from 16 Hz to 420 Hz, which is enough range to use it as a tone control on a kick or a floor tom rather than only as a rumble filter. Outputs are four rear XLRs with 1/4 inch TRS insert sends, and the optional 8-channel A-D card adds 122 dB of dynamic range.