Focusrite ISA TWO Classic Two-Channel Mic Preamp

The Focusrite ISA TWO is a 2-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 Two gives you two channels of the console preamps designed for George Martin's AIR Studios, with modern performance enhancements. The ISA Two 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 impedance settings to the classic ISA 110 setting, allowing you to match any microphone, vintage or modern, and access a wide range of sounds. The ISA Two offers both instrument and line inputs, two XLR outputs, switchable insert points, variable high-pass filter, phase reverse, and phantom power. Most of all, it provides the heritage sound of Focusrite with a touch of AIR.

Focusrite ISA TWO - Just the Facts:

• Classic ISA mic preamp design featuring Lundahl LL1538 input transformer
• Front-panel instrument inputs
• Dedicated TRS line input socket with front-panel switch
• Switchable input impedance including classic ISA 110 setting
• Dedicated insert points
• User-calibrated peak-level meters
  

Focusrite ISA TWO - Under the Hood

ISA Two incorporates two of Focusrite's renowned mic pres in a simple-to-operate 2U enclosure, placing two mic preamps, instrument inputs and line ins at your fingertips. The original Focusrite mic preamp was designed to suit the microphones of the time; today's model makes one small change, adding three additional input impedance 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.

Mic Gain Range Modes

Mode 1: With the 30-60 switch off, the stepped Gain control operates over a gain range of 0dB to +30dB, the gain setting being indicated on the front panel by the outer arc of numbers around the Gain control.

Mode 2: With the 1 switch on, the stepped gain dial operates over a gain range of +30dB to +60dB, the gain setting being indicated on the front panel by the outer arc of numbers around the gain knob. An additional 20dB of gain can be applied to the signal after the mic/line stepped gain control using the Trim control.

Line Input Gain: With the line input selected, you have access to gain settings from -20dB to +10dB in 10dB steps, indicated on the front panel by the inner arc of numbers around the stepped gain knob. An additional 20dB of gain can be applied to the signal after the stepped mic/line gain using the Trim control.

Trim - Mic or Line Modes: The Trim control provides additional gain of up to +20dB when mic or line inputs are selected. The level of trim chosen is indicated on the front panel by the inner arc of numbers around the trim knob. The additional 20dB of gain that can be applied to the mic or line signal is very useful for two reasons:

1. When high gain is required - using trim in conjunction with a mic gain of +60dB gives a maximum available gain of +80dB, making it very useful for getting good digital recording levels from very low output dynamic and ribbon microphones.

2. Gain adjustment during recording - when small amounts of gain adjustment are needed to correct performance level variations during recording, use the Trim control rather than the stepped mic/line Gain control, as switching the 10dB gain steps would be too intrusive. It is therefore good practice to apply some trim before using the 10dB stepped gain control to find the optimum recording level so that the Trim control can be used to gently add or reduce gain later, if so required.
   

Trim - Inst Input Mode: The Trim control provides variable gain of +10dB to +40dB when instrument mode is selected. The level of trim chosen is indicated on the front panel by the outer arc of numbers around the Trim control.

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.

ISA Two applications

A major element of the sound of a mic preamp is related to the interaction between the specific microphone being used and the type of mic preamp circuit it is connected to. This interaction primarily affects the level and frequency response of the microphone, as follows:

Level - A professional microphone tends to have a low output impedance and so more level can be achieved with this type of microphone by selecting the higher impedance positions of the ISA Two mic preamp.

Frequency response - Microphones with defined presence peaks and tailored frequency responses can be further enhanced by choosing different impedance settings. Choosing higher input impedance values will tend to emphasize the high frequency response of the microphone connected, allowing you to get improved ambient information and high-end clarity, even from average-performance microphones. Various microphone/ISA Two preamp impedance combinations can be tried to achieve the appropriate amount of coloration for the instrument or voice being recorded. To understand how to use the impedance selection creatively, it may be useful to read the following section on how the microphone output impedance and the mic preamp input impedance interact.

The Focusrite ISA TWO is the most affordable way to put two 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.

Mic Input Response

• Gain range: 0dB to 60dB in 10dB steps, plus 0dB to 20dB continuously variable trim
• EIN: Measured at 60dB of gain with 150 ohm source impedance and 22Hz-22kHz band pass filter -127dB
• Noise: Noise at output with unity gain (0dB) and 22Hz-22kHz band pass filter -97dBu
• Frequency response: At minimum gain (0dB): -0.5 dB at 10Hz, -1dB at 135kHz, relative to 1kHz
• At 60dB gain: -6dB at 10Hz, -1dB at 115kHz, relative to 1kHz
• Crosstalk channel-to-channel: Mic input, with I/P = 0dBu, gain = 0dB @ 1kHz input to channel A, channel B output = -85dB

Line Input Response

• Gain range: 20dB to 10dB in 10dB steps, plus 0dB to 20dB continuously variable trim
• Input impedance: 10k ohm from 10Hz to 200kHz
• Frequency response: At minimum gain (0dB) -0.3dB at 10Hz, -1dB at 80kHz, relative to 1kHz
• Crosstalk channel-to-channel: Line input, with I/P = 0dBu, gain = 0dB @ 1kHz input to channel A Channel B output?= -91dB

Instrument Input Response

• Gain range: 10dB to 40dB continuously variable trim
• Input impedance: 2M ohm
• Noise: Measured with 22Hz-22kHz band-pass filter; Minimum gain (10 dB) = -95dBu
• Frequency response (Instrument): At minimum gain (10dB) -0.1dB at 10Hz, -1dB at 115kHz, relative to 1kHz
• At Maximum Gain ( 40dB): -2.5dB at 10Hz, -1dB at 110kHz, relative to 1kHz

High-Pass Filter

• Roll-off: 18dB per octave (3-pole filter)
• Frequency range: Continuously variable from 16Hz to 420Hz (-3 dB)

Dimensions (W x D x H)

• 19" x 11" x 1-6/8" (480 x 280 x 44 mm)

Weight

8.2 lb. / 3.7 kg