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Focusrite ISA 428 Mkii

Four Classic Mic Preamps and Optional A-D Conversion

Free Tech Support


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Heritage Sound times four

Focusrite’s ISA mic preamps can be traced back to 1985, when console designer Rupert Neve was asked by Sir George Martin to create new modules for the console at AIR Montserrat. The modules he created included the legendary ISA110, on which all ISA microphone preamps are based. With their characteristic Lundahl LL1538 input transformer, along with one concession to modernity – variable input impedance – ISA mic preamps are very much the same as they were 30 years ago. But today, instead of solely gracing the consoles at AIR, ISA mic pres are at the heart of hundreds of hits made in leading studios and by leading engineers, artists and producers, across the world.

Four classic mic pres – with a little extra

Now in its second generation, the ISA 428 Mk II incorporates four of Focusrite’s renowned mic pres in a simple-to-operate 2U enclosure, placing four mic preamps, instrument inputs and line ins at your fingertips. The original Focusrite mic pre was designed to suit the microphones of the time; today’s model makes one small change, adding three additional input impedances to the classic ISA110 setting, allowing you to match any microphone, old or new, and access a wide range of sounds, from the character and warmth of a vintage mic to the clear transparency of a modern design. Or you can experiment and bring out just the qualities you want.

Front panel instrument inputs

In addition to the mic inputs, there are four front-panel instrument inputs making the ISA428 Mk II ideal for overdubs in the control room with no need for a DI box. On the back: four line inputs and switchable insert points on each channel to allow routing via external signal processors. There’s also a versatile, vintage design variable high-pass filter to control what’s going on at the bass end. And finally… accurate, 6-LED meters to tell you exactly what’s going down. Optionally available for the ISA428 Mk II is a precision eight-channel A-D converter with 122dB dynamic range and superb jitter performance – ideal for simple interfacing with your DAW.


Preamp TypeSolid State
Number of Channels4
Frequency Response20Hz-122kHz
Phantom PowerYes
Analog Inputs4 x XLR (Mic), 4 x 1/4" (Line), 4 x 1/4" (Hi-Z), 4 x 1/4" (Returns), 4 x XLR (Aux)
Analog Outputs4 x XLR, 4 x 1/4" (Sends)
Digital OutputsOptional A/D expansion card available (digital DB25, optical)
Rack Spaces2U
Weight12.2 lbs.
Manufacturer Part NumberMOIF428MK2


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