Focusrite ISA Two Dual-Channel Transformer Mic Preamp

The Focusrite ISA Two is a dual-channel transformer-based mic preamp featuring two independent ISA preamp circuits with Lundahl LL1538 input transformers in a 1U rackmount chassis, based on the original ISA 110 topology from the Focusrite Studio Console.

Preamp Controls

Each channel offers up to 80dB of gain (60dB in 10dB steps, plus 20dB of variable trim) with four-position input impedance switching (600Ω, 1.4kΩ ISA 110, 2.4kΩ, 6.8kΩ). A variable high-pass filter with continuously adjustable cutoff from 16Hz to 420Hz at 18dB/octave provides precise low-end control per channel. Front-panel instrument inputs with over 2MΩ impedance eliminate the need for external DI boxes.

Insert Points and Metering

Rear-panel balanced insert points on each channel allow inline routing to external compressors or EQs. User-calibrated 8-segment LED meters display peak signal level in dBFS, with a rear-panel calibration pot to match your A-D converter's reference level.

Connectivity

• 2 x XLR mic inputs (rear panel)
• 2 x 1/4" TRS line inputs (rear panel)
• 2 x 1/4" TS instrument inputs (front panel)
• 2 x XLR balanced outputs
• 2 x 1/4" TRS insert send/return (rear panel)

Specifications

• Mic gain range: 0 to 60dB (10dB steps) + 20dB trim
• Line gain range: -20 to +10dB (10dB steps) + 20dB trim
• Instrument gain: +10 to +40dB (continuous)
• Mic input impedance: 600Ω, 1.4kΩ (ISA 110), 2.4kΩ, 6.8kΩ
• Instrument impedance: >2MΩ
• Variable high-pass filter: 16-420Hz, 18dB/octave
• Phantom power: +48V, individually switchable
• Max output level: +24dBu
• Frequency response: 10Hz to 135kHz
• Form factor: 1U rackmount, 19" x 1.75" x 11"
• Weight: 8.16 lbs (3.7 kg)
• Power: Internal PSU, 100-240V AC