You may only need a couple of mic preamps, but they need to be the very best. The ISA Two dual-mono mic pre is the ideal solution: two independent channels of the highest quality classic Focusrite mic pres, with line in and front-panel instrument inputs – no DI box required. Based on the legendary designs found in the Focusrite Forte and Studio Consoles, ISA Two is the ideal front-end for your rack.

Superb sound spanning four different decades

Focusrite’s microphone preamplifiers go back to the original Focusrite ISA 110 modules, when Rupert Neve was commissioned by George Martin in 1985 to create a no-compromise channel strip for his Neve console. Combining the very best solid-state electronics with transformer coupling, Focusrite mic pres have played a key part in the recording of hundreds of hit records and they’re the choice of leading artists, producers and engineers around the world.

Lundahl Transformers

At the heart of the ISA Two is a pair of Lundahl LL1538 transformers. ISA products have relied on Lundahl from the beginning, since their components were originally specified in 1985. The LL1538 features a 3-section winding, resulting in very low leakage inductance and, as a result, an extended frequency response. They’re encapsulated in mu-metal cans to shield them from stray magnetism.

Variable input impedance and up to 80 dB of gain

ISA Two features two classic Focusrite mic preamps, with four impedance settings including the original ISA 110 setting. Variable input impedance allows you to go for an accurate, transparent sound or choose to highlight the character of your favourite vintage mic – and anywhere in between. With up to 80 dB of low-noise gain, ISA Two can perform in the most demanding situations - really bringing your ribbon, condenser or moving coil mics to life.

Insert your choice of processors

Each channel has a fully-balanced insert point accessed via TRS sockets on the rear panel and activated with a front-panel button, so it’s easy to use outboard processors with the ISA Two. Just plug in your choice of EQ, compressor or limiter.

Specifications

Two channel classic Focusrite ISA transformer-based preamps

Front panel, per channel:

• 1/4" instrument input
• Variable input impedance - Low, ISA 110, Medium, High
• Input selection - Mic, Line, Instrument
• 0 - 30 dB/30 - 60 dB gain switch
• Phantom power switch
• Phase invert switch
• 0 - 60 dB gain in 10 dB steps
• 0 - +20 dB continuously variable trim
• Variable high-pass filter with on/off switch
• Insert point on/off switch
• Eight-LED user-calibrated level meters
• Single power switch

Rear panel, per channel:

• XLR-F mic inputs
• 1/4" TRS line inputs
• 1/4" TRS Sends
• 1/4" TRS Returns
• XLR-M line output
• Single peak meter calibration dial
• Single IEC power socket

Measured Performance

Maximum Input and Output Levels

Maximum Output Level	+24 dBu with a THD+N < 0.01% at 1kHz measured with 150 O source impedance and 22Hz/22kHz band-pass filter
Maximum Microphone Transformer Input Level	+7 dBu with a THD+N < 0.7% at 1kHz measured at 0 dB of gain with 150 O source impedance and 22Hz/22kHz band-pass filter

Mic Input Response

Gain range 0 dB to +60 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim Input Impedance Switched Impedance setting Equivalent Input Impedance at 1 kHz Low = 600 O ISA 110 = 1.4 kO Med = 2.4 kO High = 6.8 kO EIN (Equivalent Input Noise) Measured at 60 dB of gain with 150 O source impedance and 22 Hz-22 kHz band pass filter -127 dB Noise Noise at output with unity gain (0 dB) and 22 Hz-22 kHz band pass filter -97 dBu Signal-to-Noise Ratio Measured with 150 O source impedance and 22 Hz-22 kHz band pass filter 121 dB relative to max output +24 dBu Total Harmonic Distortion + Noise Measured with a -20 dBu input signal at +30 dB of gain and with a 22 Hz-22 kHz band pass filter < 0.0007% at 1 kHz Frequency Response At minimum gain (0 dB) -0.5 dB at 10 Hz, -1 dB at 135 kHz, relative to 1 kHz At +60 dB gain -6 dB at 10 Hz, -1 dB at 115 kHz, relative to 1 kHz CMRR (Common Mode Rejection Ratio) -94 dB for mic input at 60 Hz for max. output = +24 dBu -91 dB for mic input at 10 kHz for max. output = +24 dBu Crosstalk Channel to Channel Mic input, with I/P = 0 dBu, gain = 0 dB @ 1 kHz input to channel A, channel B output = -85 dB

Line Input Response

Gain Range	-20 dB to +10 dB in 10 dB steps, plus 0 dB to +20 dB continuously variable trim
Input Impedance	10 kO from 10 Hz to 200 kHz
Noise	Noise at main output with gain at unity (0 dB) measured with 50 O source impedance and a 22Hz - 22 kHz band pass filter	-97 dBu
Signal-to-Noise Ratio	Measured with 50 O source impedance and a 22 Hz-22 kHz band pass filter	121 dB relative to max output +24 dBu
Total Harmonic Distortion + Noise	Measured with a 0 dBu input signal, +10 dB of gain and a 22 Hz-22 kHz band pass filter	< 0.002% at 1 kHz
Frequency Response	At unity gain (0 dB)	-0.3 dB at 10 Hz, -1 dB at 80 kHz, relative to 1 kHz
Crosstalk Channel to Channel	Line input, with I/P = 0 dBu, gain = 0dB @ 1 kHz input to channel A	Channel B output = -91 dB

Instrument Input Response

Gain Range	+10 dB to +40 dB continuously variable trim
Input Impedance	> 2 MO
Noise	>Measured with 22 Hz-22 kHz band pass filter	Minimum gain (+10 dB) = -95 dBu
Frequency Response	At minimum gain (+10 dB)	-0.1 dB at 10 Hz, -1 dB at 115 kHz, relative to 1 kHz
	At maximum gain (+40 dB)	-2.5 dB at 10 Hz, -1 dB at 110 kHz, relative to 1 kHz

High-Pass Filter

Roll-Off	18 dB per octave (3 pole filter)
Frequency Range	Continuously variable from 16 Hz to 420 Hz (-3 dB)

Weight and Dimensions

W x D x H	480 mm x 280 mm x 44 mm
Weight	3.7 kg