Focusrite Pro ISA 428 mk II

4-channel microphone preamplifier, based on transformer-based preamps, in a robust 2U chassis. Unique, transparent sound that characterises the ISA series since 1985.

Optional analog-to-digital converter card, compatible with ISA828 and ISA 428 mk II, offers unmatched accuracy and performance in digital-to-analog converters, equipped with PCM4220 chips with a dynamic range of 122dB and a jitter of less than 250 picoseconds. This card, via the 25-pin D-type connection, allows instant integration with most professional DAWs such as ProTools.

The microphone inputs feature a variable impedance circuit, selectable from the front panel, allowing for the optimal setting for the chosen microphone. The 4 instrument inputs on the front panel are similarly equipped with impedance selection options (high and low). Each channel also includes a switch for insert, as well as a vintage high-pass filter (75Hz, 18dB/octave), phantom power, and a phase inverter. 

Specifications

• Microphone Inputs
• gain range: 0dB-60dB in 10dB steps
• input impedances: 600Ohm, 1k4Ohm, 2k4Ohm, 6k8Ohm
• EIN of -126dB at 60dB gain
• noise at main output at unity gain (0dB): -98dBu
• SNR relative to 0dBFS (+22dBu): 120dB
• SNR relative to maximum output of 25dBu: 123dB
• THD at medium gain (30dB): 0.0009%
• frequency response at 0dB: -0.35dB at 20Hz and -3dB at 122kHz
• frequency response at maximum gain (60dB): -2.5dB at 20Hz and -3dB at 85kHz
• Line Inputs
• gain range: -20dB to +10dB in 10dB steps
• input impedance: 10kOhm
• noise at main output at 0dB gain: -91dBu measured with a band-pass filter at 22Hz-22kHz.
• SNR relative to maximum output level (25dBu): 116dB
• SNR relative to 0dBFS (+22dBu): 113dB
• THD at 0dB gain: 0.002% measured with an input signal at 0dBu with a band-pass filter 22Hz-22kHz
• frequency response at unity gain (0dB): below -0.3dB at 20Hz and below -3dB at 94kHz
• Instrument Input
• gain range: 10dB-40dB adjustable with continuous values
• input impedance: >1MOhm
• noise at minimum gain (+10dB): -95dBu measured with a band-pass filter 20Hz-22kHz
• THD at minimum gain (+10dB): 0.006% measured with a -20dBu signal at the input with a band-pass filter 22Hz-22kHz
• frequency response at a gain of 10dB with an input signal of +10dB: -0.2dB at 20Hz and 0dB at 200kHz
• frequency response at a gain of 40dB: -3dB at 20Hz and -3dB at 38.4kHz
• High-pass Filter
• 18dB per octave attenuation
• Connections
• analog inputs:
• 4 instrument inputs on 1/4" TS jacks on the front panel
• 4 microphone inputs on XLR on the rear panel
• 4 line inputs 1/4" TRS on the rear panel
• 4 insert returns on 1/4" TRS on the rear panel
• 4 ADC inputs on XLR on the rear panel
• analog outputs:
• 4 XLR outputs on the rear panel
• 4 sends on 1/4" TRS on the rear panel
• Dimensions: 480 x 88 x 280mm, 5.5kg