Focusrite ISA 428-MK2 4-Channel Microphone Preamp

The Focusrite AMS-ISA 428-MK2 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 ISA 110 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.

Each mic pre has the option of mic, line or the front-panel instrument input, with variable input impedance to ensure you are getting the best performance from the source. Up to 60dB of gain is available on the four-position rotary and gain range switches, with a further +20dB of continuously variable trim, meaning a huge 80dB of gain is available should it be required. The high-pass filter features variable cut-off frequency between 16 and 420Hz. An array of 6-segment LED meters show peak signal level for the four mic pres, in addition to the four direct inputs to the optional A-D card. Switchable rear-panel insert points allow the use of inline processors such as compression.

Features:

• Classic ISA mic preamp design featuring Lundahl LL1538 input transformer
• Instrument and line inputs with dedicated input connectors and front-panel switch
• Switchable input impedance including classic ISA 110 setting
• Variable cut-off frequency high-pass filter
• Dedicated switchable insert point
• Per-channel six-segment LED peak-level meters
• Optional A-D card with up to 192kHz, 24-bit sampling via ADAT or AES3

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MIC INPUTS

• Frequency Response At Minimum Gain (0dB) (Mic): -0.35dB at 20Hz and –3dB at 122kHz
• Frequency Response At Maximum Gain (60dB) (Mic): –2.5dB at 20Hz and –3dB 103kHz
• Gain Range (Mic): 0dB to 60dB in 10dB steps, plus 0dB to 20dB continuously variable trim
• Maximum Headroom (Mic): 7.4dBu
• Noise EIN (Mic): -126dB (measured at 60dB of gain with 150O termination and 20Hz/22kHz bandpass filter)
• Noise At Main Output With Unity Gain (Mic): -98dBu (measured with a 20Hz/22kHz bandpass filter)
• SNR (Mic): 123dB (relative to max output 25dBu) 120dB (relative to 0dBFS ( 22dBu)
• CMRR (Mic): 88dB
• Input Impedance, Variable (Mic): 600O, 1400O, 2400O, 6800O

LINE INPUTS

• Frequency Response At Unity Gain (0dB) (Line): -0.3dB at 20Hz and –3dB at 94kHz
• Gain Range (Line): -20dB to 10dB in 10dB steps, plus 0dB to 20dB continuously variable trim
• Maximum Headroom (Line): 25.4dBu
• THD N (Line): 0.002 (measured with 4dBu input signal, 0dB gain setting, with a 20Hz/22kHz bandpass filter)
• Noise At Main Output With Unity Gain (Line): -91dBu (measured with a 20Hz/22kHz bandpass filter)
• SNR (Line): 116dB (relative to max output 25dBu) 113dB (relative to 0dBFS 22dBu). Input Impedance: 10kO
• Frequency Response At 10dB Gain (Instrument): -0.2dB at 20Hz and 0dB at 200kHz
• Frequency Response At 40dB Gain (Instrument): -3dB at 20Hz and –3dB at 38.4kHz

INSTRUMENT INPUTS

• Gain Range (Instrument): 10dB to 40dB continuously variable
• Maximum Headroom (Instrument): 11.5dBu
• Noise At Main Output With Minimum Gain ( 10dB) (Instrument): -95dBu (measured with a 20Hz/22kHz bandpass filter)
• Input Impedance (Instrument): >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)

FRONT AND REAR CONNECTIVITY

• Analogue Audio Outputs (Outputs 1-4): 4 line XLR outputs on rear panel, 4 insert send 1/4” TRS jacks on rear panel
• Other I/O: IEC power input connector 100Vac – 240Vac

WEIGHT AND DIMENSIONS

• Weight: 5.5kg (12.2lbs)
• Dimensions: 80mm (W) x 88mm (H) x 280mm (D)