Originally featured on BroadcastEngineering.com
Focusrite upgrades ISA428 four-channel mic preamp
Focusrite has expanded its ISA range of pro audio hardware with the ISA428 MkII, a premium four-channel mic preamp and A-D converter. The Focusrite ISA428 MkII retains the classic ISA sound with more convenient operation at a more affordable price.
Like its predecessor, the ISA428 MkII features four of Focusrite’s transformer-based ISA preamps. Each channel has phantom power and phase-reverse controls, plus switchable input impedance and an adjustable high-pass filter. Front-panel jacks make it easy to accommodate instrument inputs.
Mirroring the feature set of the original model, the MkII also has an optional eight-channel A-D converter upgrade, which converts signals from the preamps, and an additional four line-level inputs to 24-bit digital data streams at sample rates of up to 192kHz with a 122dB dynamic range. New to the ISA428 MkII is a switched-mode power supply, which lowers the internal noise and heat output while greatly reducing its weight.
When designing the ISA428 MkII, the Focusrite R&D team was determined to maintain the pristine sound quality of its predecessor. Thus, the analog circuit board in the new Mk II is identical to the one found in the original.
The most noticeable difference is the removal of the large moving-coil peak meters of the ISA428. Metering duties on the MkII are handled by per-channel, six-step LED bargraph displays, which monitor the signal prior to the A-D stage, providing an accurate status of the preamp’s output level. Also removed is the soft limiter feature of the ISA428.