Overview
Focusrite AMS-ISA428MK2
Focusrite’s ISA mic preamps can be traced back to 1985, when console designer Rupert Neve was asked by Sir George Martin to create new modules for the console at AIR Montserrat. The modules he created included the legendary ISA110, on which all ISA microphone preamps are based. With their characteristic Lundahl LL1538 input transformer, along with one concession to modernity – variable input impedance – ISA mic preamps are very much the same as they were 30 years ago. But today, instead of solely gracing the consoles at AIR, ISA mic pres are at the heart of hundreds of hits made in leading studios and by leading engineers, artists and producers, across the world.
Now in its second generation, the ISA 428 Mk II incorporates four of Focusrite’s renowned mic pres in a simple-to-operate 2U enclosure, placing four mic preamps, instrument inputs and line ins at your fingertips. The original Focusrite mic pre was designed to suit the microphones of the time; today’s model makes one small change, adding three additional input impedances to the classic ISA110 setting, allowing you to match any microphone, old or new, and access a wide range of sounds, from the character and warmth of a vintage mic to the clear transparency of a modern design. Or you can experiment and bring out just the qualities you want.
In addition to the mic inputs, there are four front-panel instrument inputs making the ISA428 Mk II ideal for overdubs in the control room with no need for a DI box. On the back: four line inputs and switchable insert points on each channel to allow routing via external signal processors. There’s also a versatile, vintage design variable high-pass filter to control what’s going on at the bass end. And finally… accurate, 6-LED meters to tell you exactly what’s going down. Optionally available for the ISA428 Mk II is a precision eight-channel A-D converter with 122dB dynamic range and superb jitter performance – ideal for simple interfacing with your DAW.
Features
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Four ISA series transformer-based preamps
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Eight-channel optional A-D converter
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Selectable impedance
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Four front panel instrument inputs
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Dedicated analogue insert points
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Accurate LED meters for every channel
Specifications
Mic Inputs
| 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 150Ω 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 | 600Ω, 1400Ω, 2400Ω, 6800Ω |
Line Inputs
| 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: 10kΩ |
Instrument Inputs
| 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 = >1MΩ |
