Focusrite ISA Two 2-channel Mic/Instrument Preamp

Manufacturer's Description

Focusrite ISA Two Classic Dual Mono Transformer-Based Microphone Preamplifier

Twin channels of exquisite pre-amplification, with front-panel DI for easy instrument connection.The ISA Two is the ideal front-end solution for any studio rack, with two independent channels of Focusrite’s high-quality microphone preamps, each with their own front-panel instrument inputs, so no additional DI boxes are required. Based on the legendary designs found in the Focusrite Forte and Studio Consoles, ISA Two will easily integrate into any audio signal path.

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 favorite 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.

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

Maximum Input and Output Levels

• Maximum Output Level: +24 dBu with a THD+N < 0.01% at 1kHz measured with 150 Ω 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 Ω 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 1kHz
• Low = 600 Ω
• ISA 110 = 1.4 kΩ
• Med = 2.4 kΩ
• High = 6.8 kΩ
• EIN (Equivalent Input Noise): Measured at 60 dB of gain with 150 Ω source impedance and 22 Hz-22kHz band pass filter = -127 dB
• Noise: Noise at output with unity gain (0 dB) and 22 Hz-22kHz band pass filter = -97 dBu
• Signal-to-Noise Ratio: Measured with 150 Ω source impedance and 22 Hz-22kHz 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 1kHz
• Frequency Response:
• At minimum gain (0 dB)
• -0.5 dB at 10 Hz, -1 dB at 135kHz, relative to 1kHz
• At +60 dB gain
• -6 dB at 10 Hz, -1 dB at 115kHz, relative to 1kHz
• 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 @ 1kHz 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 kΩ from 10Hz to 200kHz
• Noise: Noise at main output with gain at unity (0 dB) measured with 50 Ω source impedance and a 22Hz - 22 kHz band pass filter = -97 dBu
• Signal-to-Noise Ratio: Measured with 50 Ω source impedance and a 22Hz-22kHz 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 22Hz-22kHz band pass filter = < 0.002% at 1kHz
• Frequency Response:
• At unity gain (0 dB) -0.3 dB at 10Hz, -1 dB at 80kHz, relative to 1kHz
• Crosstalk Channel to Channel: Line input, with I/P = 0 dBu, gain = 0dB @ 1kHz 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 MΩ
• Noise: >Measured with 22Hz-22kHz 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

• Dimensions (WxHxD): 18.90” x 1.73” x 11.02” (480 mm x 44 mm x 280 mm)
• Weight: 8.16lb

Features

• Lundahl LL1538 mic input transformer maintains flat frequency response across wide bandwidths
• Up to 80 dB of clean, distortion-free gain
• Four choices of input impedance
• User-calibrated metering
• Front-panel instrument and rear panel line inputs
• Variable cut-off high-pass filter
• Rear panel balanced inserts