Retro Gear Shop is a high-end boutique store located in Nashville, Tennessee. Focusrite ISA-428 For sale is a Focusrite ISA428 4 channel microphone preamp. We gave this unit a brief test on the analog portion of this unit (we do not have a setup to test the digital portion) and found channels 1-3 appear to be working as they should. Channel 4 did not seem to pass audio signal. We also found some of the buttons did not light up but that could have been user error. Check out the pictures to make sure you like it.