New to Focusrite's renowned ISA range of pro audio hardware is the ISA428 MkII, a premium four-channel microphone preamp supporting an optional eight-channel A-D converter. The ISA428 MkII supersedes the existing ISA428 and will be available at a much more affordable price.
The ISA428 MkII features four of Focusrite's classic ISA preamps, originally developed for the legendary Forté console. It supports the same professional eight-channel A-D converter option used with the ISA828. The A-D converter accepts four line inputs in addition to the signals passing through the main channels of the ISA428 MkII, creating eight high-quality digital streams with a superb 122dB dynamic range. Thanks to its convenient 25-pin D-Type connector, the A-D converter option integrates seamlessly with most digital workstations, including Pro Tools HD.
Mirroring the feature set of the original, each ISA428 MkII channel has a variable impedance circuit allowing you to perfectly match the preamp with any microphone, or to use different settings creatively to shape the sound of the microphone. Adjustable high-pass filters as well as phantom power and phase reverse controls are easily accessible on the front panel.
When designing the ISA428 MkII, the Focusrite R&D team were determined to maintain the pristine audio fidelity of its predecessor, but introduce it at a new level of affordability. To that end, the exact same analogue circuit board can be found in both the original and MkII derivations of the ISA428.
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.
First introduced in 1985, the ISA microphone preamp holds a reputation for outstanding transparency along with subtle warmth contributed by transformer core saturation. The addition of a variable impedance circuit allows ISA you to perfectly match the preamp with any microphone, or to use different settings creatively to shape the sound of the microphone. Unchanged for decades, the ISA microphone preamp topology offers incredible clarity and the signature Focusrite sound that makes it the top choice among many audio professionals today.
Four ISA series transformer-based preamps?
ISA series microphone 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. More information can be found here.
Ideal for microphone 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 pre-amp 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.?
Phantom power available on every channel
Trim control allows 20dB of extra gain with fine adjustment
Phase reverse buttons help to correct phase issues with microphones or cables
Optional A-D converters easily synchronise to external word clock
Frequency response at minimum gain (0dB): -0.35dB at 20Hz and -3dB at 122kHz
Frequency response at maximum gain (60dB): -2.5dB at 20Hz and -3dB 103kHz
Gain range: 0dB to +60dB in 10dB steps, plus 0dB to +20dB continuously variable trim
Maximum headroom: +7.4dBu
THD+N: 0.0009% (measured at 1kHz -20dBu input signal, at 30dB gain setting, with a 20Hz/22kHz bandpass filter)
Noise EIN: -126dB (measured at 60dB of gain with 150O termination and 20Hz/22kHz bandpass filter)
Noise at main output with unity gain: -98dBu (measured with a 20Hz/22kHz bandpass filter)
SNR: 123dB (relative to max output 25dBu)
SNR: 120dB (relative to 0dBFS (+22dBu)
Input Impedance, variable: 600O, 1400O, 2400O, 6800O
Frequency Response at unity gain (0dB): -0.3dB at 20Hz and -3dB at 94kHz
Gain range: -20dB to +10dB in 10dB steps, plus 0dB to +20dB continuously variable trim
Maximum headroom: +25.4dBu
THD+N: 0.002% (measured with +4dBu input signal, 0dB gain setting, with a 20Hz/22kHz bandpass filter)
Noise at main output with unity gain: -91dBu (measured with a 20Hz/22kHz bandpass filter)
SNR: 116dB (relative to max output 25dBu)
SNR: 113dB (relative to 0dBFS +22dBu). Input Impedance: 10kO
Frequency Response at +10dB gain: -0.2dB at 20Hz and 0dB at 200kHz
Frequency Response at +40dB gain: -3dB at 20Hz and -3dB at 38.4kHz
Gain range: +10dB to +40dB continuously variable
Maximum headroom: +11.5dBu
THD+N: 0.006% (measured with -20dBu input signal, at minimum gain (+10dB), with a 20Hz/22kHz bandpass filter)
Noise at main output with minimum gain (+10dB): -95dBu (measured with a 20Hz/22kHz bandpass filter)
Input Impedance = >1MO
High Pass Filter
Roll off = 18dB per octave 3 pole filter
Frequency range: 16Hz to 420Hz (continuously variable, measured at the 3dB down point)
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
?Front and rear connectivity
Analogue Channel Inputs (Inputs 1-4)
4 instrument 1/4" TS jack inputs on front panel
4 microphone XLR inputs on rear panel
4 line 1/4" TRS jacks on rear panel
4 insert return 1/4" TRS jacks on rear panel
4 ADC XLR inputs on rear panel
Analogue Audio Outputs (Outputs 1-4)
4 line XLR outputs on rear panel
4 insert send 1/4" TRS jacks on rear panel
IEC power input connector 100Vac - 240Vac
Front Panel Indicators
8 output meters, 6 segment
4 30-60 microphone gain range selection indicator
4 +48V phantom power indicator
4 Phase indicator
4 Insert In indicator
4 Filter In indicator
4 Input selection indicators (Mic, Line, Inst)
4 Z In microphone input impedance selection indicators (Low, ISA110, Med, High) Clock select indicators (44.1, 48, 88.2, 96, 176.4, 192)
Ext clock indicators (Lock, Word clock, 256X)
Dimensions (W x H x D)
480mm (W) x 88mm (H) x 280mm (D)
19" (W) x 3.5" (H) x 11" (D)
Focusrite warrants its products to be free from defects for 1 year from the date of purchase.
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