Focusrite ISA 428 MkII Microphone Preamp

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 users 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. Phantom power available on every channelTrim control allows 20dB of extra gain with fine adjustment Phase reverse buttons help to correct phase issues with microphones or cablesOptional A-D converters easily synchronise to external word clockThe optional class-leading eight-channel A-D converter option used with the ISA828 is also compatible with the ISA428 MkII. Along with the four mic preamp inputs, four additional inputs allow you to route other line signals through the converter.

Four instrument inputs, instantly accessible on the front panel, allow quick and easy connection without the need for a separate DI box. Extra processing can be placed between preamp and conversion via the units dedicated insert points, featured on every channel. Finally, accurate six-segment LED metering is designed to catch even the fastest transients on every channel.
Features: Four ISA series transformer-based preampsISA series mic preamps have been the producers’ choice on countless hit records over the last two decades. Eight-channel optional A-D converterFour 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 impedanceIdeal for mic matching or extended microphone creativity. Settings include the ‘Vintage ISA110’ setting, providing the original Focusrite signature sound. Four front panel instrument inputsInstant access on the front fascia - no separate DI box required. Dedicated analogue insert pointsSwitchable insert points are featured on every channel, allowing routing (between preamp and output) through additional external processing. Variable high-pass Focusrite filterProvided on every channel, this is the same filter as featured on the original ISA428. Accurate LED meters for every channelClear metering designed to catch even the fastest and most elusive of transients. Mic InputsFrequency response at minimum gain (0dB): - 0.35 dB at 20Hz and –3dB at 122kHzFrequency response at maximum gain (60dB): – 2.5 dB at 20Hz and –3dB 103kHzGain range: 0dB to +60dB in 10dB steps, plus 0dB to +20dB continuously variable trim•Maximum headroom: +
7.4 dBuTHD+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)CMRR: 88dB.
Input Impedance,
variable: 600O, 1400O, 2400O, 6800OLine InputsFrequency Response at unity gain (0dB): - 0.3 dB at 20Hz and –3dB at 94kHzGain range: -20dB to +10dB in 10dB steps, plus 0dB to +20dB continuously variable trimMaximum headroom: +
25.4 dBuTHD+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