Focusrite ISA Two

Focusrite ISA Two — a two-channel microphone preamp built around the Lundahl LL1538 transformer and a circuit derived directly from the original ISA 110 module, designed as a purely analogue source feeding any external converter or interface.

Each of the two independent channels offers mic, line and front-panel DI inputs, switchable input impedance, a balanced insert point, and a variable high-pass filter with a cutoff sweepable from 16 to 420 Hz. Unlike the ISA One, ISA Two has no slot for a digital card — the output is analogue only, meant to feed an external A-D converter, interface or console.

Matching input impedance to any microphone, vintage included

Four selectable input impedance values, including the original ISA 110 setting, let you tailor tonal character to a specific microphone rather than settling for one compromise setting — a lower impedance gives a more transparent, modern result, while a higher one restores the warmth typical of vintage tube or ribbon mics from the 60s and 70s. The setting is remembered after power-down, so a configuration dialled in for a particular mic doesn't get lost between sessions.

80 dB of gain headroom and an insert without leaving the analogue path

Stepped gain from 0 to 60 dB in 10 dB increments, plus a continuously variable trim up to +20 dB, gives up to 80 dB of gain in total — enough headroom for quiet acoustic sources without pushing the noise floor higher than needed. A balanced insert on each channel, switched in from the front panel, lets you patch in an outboard EQ or compressor directly within the preamp's signal path, and 8-segment LED metering with a rear-panel calibration control keeps the signal aligned with whatever converter or DAW is on the receiving end.

KEY FEATURES

• 2 independent microphone preamps with Lundahl LL1538 transformer
• 4 switchable input impedances, remembered after power-down
• Mic gain 0-60 dB in 10 dB steps plus up to +20 dB trim (up to 80 dB total)
• Rear-panel line input and front-panel DI
• Variable high-pass filter, 16-420 Hz
• Polarity inversion on each channel
• Balanced send/return insert, switched in from the front panel
• 8-segment LED metering with calibrated reference level
• Analogue output only — no digital card slot
• Rugged, all-metal enclosure

TECHNICAL SPECIFICATIONS

• Channels: 2 independent microphone preamps
• Mic gain: 0-60 dB in 10 dB steps plus 0-20 dB trim
• EIN: -127 dBu at 60 dB gain (150 Ohm source, 22 Hz-22 kHz filter)
• Line gain: -20 to +10 dB in 10 dB steps plus trim
• Instrument gain: 10-40 dB, continuously variable
• Input impedance: 4 switchable values, including original ISA 110 setting
• HPF: 16-420 Hz, variable
• THD+N (line): 0.0001% at 0 dBu
• Insert: balanced send/return on TRS jack per channel
• Metering: 8-segment LED, calibrated reference level