Focusrite ISA 828 MkII 8-Channel Transformer Mic Preamp

Overview

The Focusrite ISA 828 MkII is a professional eight-channel transformer-based microphone preamp designed for studios, tracking rooms, mobile recording rigs, and permanent rack installations. Based on the classic ISA 110 microphone preamp design, it combines eight Focusrite ISA preamps with Lundahl LL1538 input transformers for detailed, high-quality recording with flexible tonal options.

Each channel supports microphone or line-level sources, while channels 1–4 also provide dedicated front-panel instrument inputs. With up to 80dB of total gain, selectable microphone impedance, switchable 75Hz high-pass filtering, phase reversal, independent phantom power, calibrated LED metering, and optional digital expansion, ISA 828 MkII provides a versatile front end for multi-channel recording.

Key Features

• Eight classic Focusrite ISA transformer-based microphone preamps
• Lundahl LL1538 input transformers on every microphone input
• Up to 60dB of stepped gain plus 20dB continuously variable trim
• Up to 80dB total gain range
• Four selectable microphone input impedance settings
• Eight dedicated microphone inputs and eight line-level inputs
• Four front-panel instrument inputs on channels 1–4
• High and Low impedance options for the instrument inputs
• Switchable 75Hz high-pass filter on every channel
• Independent +48V phantom power and phase reversal per channel
• Switchable rear-panel insert points
• Calibratable six-segment LED peak meters for each channel
• Eight balanced analogue outputs on an AES59/TASCAM DB-25 connector
• Optional ISA ADN8 digital expansion with Dante, ADAT, and AES3
• Up to 24-bit/192kHz operation with the optional digital card
• Efficient updated switched-mode power supply
• Professional 2U rackmount construction

Eight Classic ISA Preamps

The ISA 828 MkII brings eight of Focusrite's renowned ISA microphone preamps into a single rackmount unit. Every microphone input uses a Lundahl LL1538 transformer, delivering the characteristic ISA approach to transparent yet musically engaging microphone amplification.

Each channel offers up to 60dB of stepped gain together with an additional 20dB of continuously variable trim, providing up to 80dB of total gain. This wide range makes the preamps suitable for everything from strong line-level sources to microphones requiring substantial clean gain.

Selectable Microphone Impedance

Each microphone input provides four selectable impedance settings: Low, ISA 110, Medium, and High. The ISA 110 setting recreates the impedance associated with the original Focusrite ISA microphone preamp, while the additional settings allow engineers to optimize the interaction between different microphones and the preamp.

Microphone and Line Inputs

Dedicated microphone and line-level connectors allow sources to remain connected simultaneously, making the ISA 828 MkII especially practical for permanent studio installations. The front-panel input selection controls let you choose the appropriate source for each channel without repeatedly reconnecting equipment.

Four Direct Instrument Inputs

Channels 1–4 feature convenient front-panel 1/4-inch instrument inputs for directly recording guitars, basses, keyboards, and other instrument-level sources. Each instrument input offers High and Low impedance choices, allowing the preamp to accommodate different instruments and pickup configurations.

High-Pass Filtering and Signal Control

Every channel includes a switchable 75Hz high-pass filter with an 18dB-per-octave slope. It can help reduce low-frequency rumble, stand-borne vibration, proximity effect, and other unwanted low-end energy before the signal reaches the recording system.

Independent +48V phantom power and phase reversal are also available on each channel, providing essential control for professional microphone recording and multi-source tracking.

Analogue Inserts

ISA 828 MkII provides switchable rear-panel insert points for integrating external analogue processors such as compressors and equalisers. When used with the optional ISA ADN8 digital card, the insert function can also be incorporated into the digital signal path for expanded processing workflows.

Accurate Channel Metering

Each channel features a calibratable six-segment LED peak-level meter, allowing engineers to monitor signal levels clearly across all eight preamps. Meter calibration can be adjusted to suit the requirements of different analogue and digital recording systems.

Optional Digital Expansion

The ISA 828 MkII supports the optional ISA ADN8 eight-channel A-D converter card. The expansion provides high-quality digital outputs over Dante, ADAT, and AES3, with sample rates up to 24-bit/192kHz. This allows the eight ISA preamps to integrate directly with compatible digital audio interfaces, consoles, DAWs, and networked audio systems.

The ISA ADN8 is sold separately and is not included with the standard ISA 828 MkII.

Efficient Rackmount Design

The updated switched-mode power supply in the ISA 828 MkII is designed for more efficient operation and reduced heat generation compared with the previous model. Its professional 2U rackmount format makes it suitable for permanent installation in studio racks, recording facilities, and mobile production systems.

Typical Uses

• Multi-channel vocal and microphone recording
• Drum and percussion tracking
• Acoustic instrument recording
• Guitar and bass DI recording through channels 1–4
• Multi-microphone studio sessions
• External compressor and EQ integration
• Professional microphone front-end expansion for audio interfaces
• Permanent studio and rack installations
• Digital studio and Dante integration with the optional ISA ADN8 card

Specifications

• Channels: 8 microphone/line preamp channels
• Mic Gain: 0–30dB or 30–60dB in 10dB steps, plus 0–20dB continuous trim
• Total Mic Gain: Up to 80dB
• Mic Input Impedance: 600Ω, 1.4kΩ, 2.4kΩ, 6.8kΩ
• Maximum Mic Input Level: +7dBu
• Mic EIN: -123dBu A-weighted typical
• Mic Signal-to-Noise Ratio: 122dB A-weighted typical
• Line Gain: -20dB to +10dB in 10dB steps, plus 0–20dB continuous trim
• Maximum Line Input Level: +25dBu
• Instrument Gain: +10dB to +40dB continuous
• Instrument Input Impedance: 470kΩ Low / 2.4MΩ High
• High-Pass Filter: 75Hz, 18dB/octave
• Microphone Inputs: 8 × XLR female
• Line Inputs: 8 × balanced 1/4-inch inputs
• Instrument Inputs: 4 × 1/4-inch front-panel inputs
• Analogue Outputs: 8 balanced outputs via AES59/TASCAM DB-25
• Digital Expansion: Optional ISA ADN8
• Digital Connectivity with ADN8: Dante, ADAT, AES3
• Maximum Digital Resolution: 24-bit/192kHz
• Format: 2U rackmount

What's Included

• Focusrite ISA 828 MkII
• AC power lead
• Safety information cut sheet

Note: The optional ISA ADN8 eight-channel A-D converter card is sold separately and is not included with the standard ISA 828 MkII.

Why Choose the Focusrite ISA 828 MkII?

The Focusrite ISA 828 MkII combines eight classic transformer-based ISA microphone preamps with flexible impedance selection, direct instrument inputs, analogue inserts, high-pass filtering, precise metering, and professional rack connectivity. With optional Dante, ADAT, and AES3 expansion through the ISA ADN8 card, it provides a powerful and adaptable recording front end for modern professional studios and multi-channel production environments.