Focusrite ISA 428 MKII Focusrite

The Focusrite ISA 428 MkII is a 4-channel preamp featuring the original ISA design, Lundahl LL1538 input transformer, switchable input impedance including classic ISA 110 setting, variable high-pass filter, instrument and line inputs, and LED peak meters.

The Focusrite ISA 428 MkII gives you four channels of the console preamps designed for George Martin’s AIR Studios, with modern performance enhancements. The ISA 428 MkII retains the classic ISA sound, which in part, comes from its Lundahl LL1538 input transformer and custom Zobel network, which imparts a special character to the sound that can’t be truly emulated in any other way. Whereas the original ISA input impedance was calculated to suit the microphones of the day, today’s model makes one small change, adding three additional input impedances to the classic ISA 110 setting, allowing you to match any microphone, vintage or modern, and access a wide range of sounds. The ISA 428 MkII offers both instrument and line inputs, four XLR outputs, switchable insert point, variable high-pass filter, phase reverse, phantom power, and an optional A-D card with up to 24-bit/192kHz sampling via ADAT or AES3. Most of all, it provides stunning sound with a touch of AIR.

Focusrite ISA 428 MkII – Just the Facts:

• 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

Focusrite ISA 428 MkII – Under the Hood

ISA 428 MkII 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 16Hz 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.

PAD – For the Record: The name Focusrite has quite a unique history. While many company names in pro audio are amalgams of founder’s surnames, such as Bricasti Designs, which combines the first names of its founders, Brian Zolner and Casey Dowdell (the “ti” was thrown in for extra gravitas), Focusrite was a generic pre-registered U.K. legal entity, used to establish a company quickly and later change its name. When Rupert Neve used it to register his new company in 1985, he decided to keep the name for its connotation of accuracy. Prior to founding Focusrite Ltd., Rupert Neve was contracted by George Martin to build 16 additional input channels for the console at AIR Studios. With a directive to spare no expense, the ISA 110/130 modules were the result, and later formed the basis for Focusrite Ltd.’s products. In 1989, after demand for Focusrite to build consoles put the company in financial jeopardy, Phil Dudderidge, formerly of Soundcraft, bought the assets of Focusrite Ltd, including the designs for the ISA modules and continued to manufacture them. For a time, Focusrite Audio Engineering Ltd. tried to distance itself from the name, Neve, since Rupert never designed any products for Dudderidge, who wanted his Focusrite Audio Engineering Ltd.’s products to be judged on their own merit. Customer demand and a fondness for audio history has kept the ISA range in production, and their association with Neve alive as well.

The Focusrite ISA 428 MkII is the most affordable way to put four channels of Neve-designed, Focusrite-improved preamps in your rack. Order yours today. For more information, call or chat online with your PAD Studio Specialist.

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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 band-pass filter)
• Noise EIN: -126dB (measured at 60dB of gain with 150 ohm termination and 20Hz/22kHz band-pass filter)
• Noise at main output with unity gain: -98dBu (measured with a 20Hz/22kHz band-pass filter)
• SNR: 123dB (relative to max output 25dBu)
• SNR: 120dB (relative to 0dBFS (+22dBu)
• CMRR: 88dB
• Input impedance, variable as follows: 6k, 14k, 24k, 68k ohm

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 band-pass filter)
• Noise at main output with unity gain: -91dBu (measured with a 20Hz/22kHz band-pass filter)
• SNR: 116dB (relative to max output 25dBu)
• SNR: 113dB (relative to 0dBFS +22dBu)
• Input Impedance: 10k ohm

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 band-pass filter)
• Noise at main output with minimum gain (+10dB): -95dBu (measured with a 20Hz/22kHz band-pass filter)
• Input Impedance >1M ohm

High-pass filter

• Roll off = 18dB per octave 3 pole filter.
• Frequency range: 16Hz to 420Hz (continuously variable, measured at the 3dB down point)

Meters 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:

Switched impedance setting (equivalent input impedance at 1kHz)

• Low: 600 ohm
• ISA110: 400 ohm
• Med (Medium): 2.4k ohm
• High: 6.8k ohm

Front and rear connectivity

Analog channel inputs (inputs 1-4) (ACD inputs 5-8)

• 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

Analog 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

Front-panel indicators

• 8 output meters, 6-segment
• 4x 30-60 mic gain range selection indicator
• 4x +48V phantom power indicator
• 4x Phase indicator
• 4x Insert indicator
• 4x Filter indicator
• 4x Input selection indicators (Mic, Line, Inst)
• 4x Hi-Z In microphone input impedance selection indicators (Low, ISA110, Med, High)
• Clock select indicators (44.1, 48, 88.2, 96, 176.4, 192kHz)
• clock indicators (Lock, Word clock, 256X)

Weight and dimensions

• Dimensions approx. W x H x D): 19″ x 3-1/2″ x 11″ (480 x 88 x 280mm)
• Net Weight:12.2 lb. (5.5kg)