Focusrite Pro ISA 428 MKII Microphone Preamp
4-Channel Microphone Preamp with A-D Conversion
The ISA428 MkII provides four of Focusrite’s prestigious transformer-based microphone preamps. It features the same classic circuitry and renowned audio quality found in the original at a new level of affordability. With selectable input impedance, direct instrument inputs and an optional eight channels of high-quality analogue to digital conversion, the ISA428 MkII creates the perfect front end for the discerning recording professional.
Focusrite’s ISA428 four-channel microphone preamplifier delivers the Focusrite trademark sound at its lowest cost per channel to date, supplying four original ISA transformer-based preamps in a single sturdy two unit chassis. The four ISA-series transformer-based microphone preamps make use of the same archetypal microphone preamplifier design as the original ISA110 module from Focusrite's legendary Forté console (including the original Lundahl L1538 transformer and bespoke zobel network).
The preamps are supplemented by four line inputs, four line outputs and a further optional four channel 192kHz A-D converter boasting a dynamic range of 122dB. The ISA428 also combines speedily and effortlessly with ProTools HD, and other popular hard disc recorders and mixing desks, because of its widely-compatible 25 pin D-Type connectors.
The microphone input stage also features a variable impedance circuit, providing the user the opportunity to alternate between four well thought out selected input impedance settings. The original ISA110 setting is complimented by three more impedance settings to either faultlessly counterbalance the preamp with a microphone, maximising level, or to use diverse settings creatively to sculpt the sound of the microphone being used.
High and low impedance options are present on the four front panel instrument inputs to deliver a complete and accessible DI solution. If the need arises to position extra processing between the preamp and converter insert switches feature on every channel. Each channel provides vintage design 75 Hz / 18dB per octave high pass filters, making certain that unwelcome low frequencies are essentially eliminated.
Four ISA series transformer-based preamps: ISA series mic preamps have been the producers’ choice on countless hit records over the last two decades
Eight-channel optional A-D converter: Four additional A-D converter inputs allow eight channels of high-quality conversion, with a dynamic range of 122dB and jitter performance below 250 picoseconds
Selectable impedance: Ideal for mic matching or extended microphone creativity. Settings include the ‘Vintage ISA110’ setting, providing the original Focusrite signature sound
Four front panel instrument inputs: Instant access on the front fascia - no separate DI box required
Dedicated analogue insert points: Switchable insert points are featured on every channel, allowing routing (between preamp and output) through additional external processing
Variable high-pass Focusrite filter: Provided on every channel, this is the same filter as featured on the original ISA428
Accurate LED meters for every channel: Clear metering designed to catch even the fastest and most elusive of transients
High Pass Filter
Meters (6 LED meter is calibrated 0dBFS = +22dBu (the maximum level which can be correctly converted by the optional internal A/D converter before overload occurs).
The meter calibration points are as follows:
Meter panel calibration value in dBFS / Equivalent dBu value
0dBFS / +22dBu
-2dBFS / +20dBu
-6dBFS / +16dBu
-12dBFS / +10dBu
-18dBFS / +4dBu
-42dBFS / -20dBu
Analogue Channel Inputs (Inputs 1-4)
Analogue Audio Outputs (Outputs 1-4)
Front Panel Indicators
Dimensions and Weight
480mm (W) x 88mm (H) x 280mm (D)