Focusrite ISA 428 (2000s)
A four-channel microphone preamplifier with instrument and line inputs, part of Focusrite's ISA Range.
Overview
The Focusrite ISA 428, including the MkII version, is a four-channel microphone preamplifier designed for professional recording applications. Built in a 2U enclosure with a distinctive blue finish, it offers independent, identical channels, each with rotary gain and trim controls. The unit supports microphone, instrument, and line inputs, making it a flexible front-end solution in studio environments. It is compatible with the optional ISA ADN8 eight-channel A-D card for high-quality analog-to-digital conversion. The ISA 428 MkII draws from the legacy of Rupert Neve’s original ISA design, influencing the sound of recorded music for decades.
Specifications
| Product type | Four-channel microphone preamplifier |
| Weight | 5.5kg (12.2lbs) |
| Power Requirements | 100VAC~240VAC |
| Power Consumption | 35 W |
| Frequency Response (Mic, Min Gain 0dB) | -0.35dB at 20Hz, -3dB at 40kHz |
| Gain Range | Up to 80dB (60dB rotary + 20dB variable trim) |
| Optional Accessories | ISA ADN8 eight-channel A-D card |
Design
The ISA 428 MkII features a front panel with rotary gain and trim controllers, a variable high-pass filter, and on/off push buttons per channel. It incorporates four of Focusrite’s classic microphone preamplifier circuits and is designed for straightforward operation in a 2U rackmount format. The unit contains no user-replaceable components, including fuses.
Context
The ISA 428 MkII is part of Focusrite’s ISA Range, which includes models like the ISA Two and ISA 828 MkII. It was positioned as a high-quality alternative to units like the Neve Portico in professional studio discussions. Its lineage traces back to Rupert Neve’s original ISA console design, which helped define the sound of recorded music over several decades.
Market
Used units have been listed from $999.90, with early 2004 listings at $1,199 and later MkII models priced around $1,722. Refurbished units are available, and some early production models were noted to run hot near the power supply—reportedly resolved in later versions.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.