Focusrite ISA428 MkII Rackmount 4-Channel Mic Preamp

Four Channel Microphone Preamp for Professional Recording Front Ends

The Focusrite ISA428 MkII is a four-channel rackmount microphone preamp designed for engineers who need pristine analog signal capture with flexible tonal control. Built around Focusrite’s legendary transformer-based preamp design, it provides four independent mic preamps in a single 2U chassis, making it an ideal front end for studio recording, broadcast production, and professional tracking environments. Whether paired with an analog console or a modern DAW, this unit delivers clean gain, musical character, and consistent performance across all channels.

Transformer Based Design with Musical Character and Clarity

Each channel in the ISA428 MkII uses a Lundahl input transformer that delivers transparency with subtle harmonic richness. This transformer-based topology preserves transient detail while adding a gentle warmth that engineers associate with classic Focusrite hardware. The wide frequency response extends well beyond the audible range, ensuring accurate phase response and open high-frequency reproduction that translates cleanly to vocals, acoustic instruments, drums, and orchestral sources.

Selectable Input Impedance for Microphone Matching and Sound Shaping

A key advantage of the ISA428 MkII is its selectable input impedance control, allowing users to optimize performance for virtually any microphone type. Multiple impedance settings let engineers match vintage ribbon microphones, modern condensers, or dynamic mics precisely, or intentionally alter impedance to shape tone creatively. This flexibility makes the preamp equally valuable for traditional recording techniques and experimental sound design.

Built In Instrument Inputs and Analog Insert Points

Each channel features a front-panel instrument input, allowing direct connection of guitars, basses, and keyboards without the need for external DI boxes. Dedicated analog insert points on every channel make it easy to integrate compressors, EQs, or other outboard processors directly into the signal path between the preamp and output. This routing flexibility supports complex studio workflows while keeping signal integrity intact.

Optional High Resolution Analog to Digital Conversion

The ISA428 MkII supports an optional eight-channel A-D converter card, expanding the unit into a powerful digital front end for Pro Tools and other DAWs. The converter design uses premium components to deliver a wide dynamic range and low jitter performance, ensuring clean and accurate digital capture. The converter can be installed at any time and connects via a 25-pin D-sub connector for easy integration with professional audio interfaces and recording systems.

Precision Controls and Visual Metering for Reliable Tracking

Every channel includes phantom power, phase reverse, trim control, and a variable high-pass filter modeled after classic Focusrite designs. High-resolution LED meters provide clear visual feedback, making it easy to monitor levels and catch fast transients during recording. These controls give engineers confidence when tracking critical performances in demanding studio and live production settings.