Focusrite ISA Two Dual-Channel Transformer Microphone Preamp with DI

A Matched Pair of Classic ISA Preamps

The Focusrite ISA Two is a two-channel transformer-based microphone preamplifier that brings together a totally independent pair of the legendary ISA mic pres from the original ISA 110 module. It combines traditional solid-state electronics with the original input transformer specified by Rupert Neve, the Lundahl LL1538, in a single 1U rackmount chassis. A transformer-coupled preamp routes each microphone signal through an input transformer before the gain stage, adding the warmth and low-end body that define the ISA sound. Two channels is the natural number for recording a vocal and an instrument together or a stereo pair, making the ISA Two an efficient, high-end front end.

The Lundahl Transformer and Zobel Network

Rupert Neve originally chose the Lundahl LL1538 as the ISA 110 input transformer, and it remains at the front of both ISA Two channels. He also perfected the Zobel network in the ISA circuit, a small arrangement of components that tames the transformer's high-frequency resonance for a smooth, extended response. Together these elements give the preamp its combination of richness and clarity that has kept the design relevant for decades. Engineers who value a proven analog pedigree find that heritage engineering intact in the ISA Two.

Up to 80dB of Clean Gain

Each channel delivers up to 80dB of clean, distortion-free gain, with the transformer supplying 20dB and the input stage providing up to 60dB more. That much gain is essential for low-output ribbon and dynamic microphones on quiet sources, where insufficient amplification would raise the noise floor with the signal. The ISA topology keeps noise low even at the highest gain settings, with a measured equivalent input noise (EIN) of -127dB. A vocalist tracked with a passive ribbon or a distant instrument mic stays clean and detailed rather than hissy.

Switchable Impedance for Microphone Matching

Four choices of input impedance, including the original ISA 110 value, let you match each preamp to its microphone, and the setting is remembered even after the unit is switched off. Impedance matching sets how the preamp loads the microphone, and choosing it shapes tone at the source by shifting frequency response and transient detail. A vintage microphone can be given the load it was voiced for while a modern capsule can be set for maximum transparency. This lets a recording engineer voice a stereo pair identically or contrast two sources deliberately.

Instrument Inputs, Inserts, and Metering

Two front-panel 1/4-inch instrument inputs provide transparent DI access, while rear-panel TRS line inputs and balanced insert points expand the routing options. A balanced insert point lets an outboard compressor or equaliser be switched into each channel from the front panel, so hardware processing can be committed on the way in. Eight-LED metering per channel, calibrated by a rear-panel control, displays peak level in dBFS to line up cleanly with the converters that follow. A project studio can integrate the ISA Two into an existing patchbay and monitoring workflow with ease.

Two Fully Independent Channels

Because the two preamps are entirely independent, each carries its own gain, impedance, filter, insert, and metering rather than sharing a single control set. Independent channels mean a vocal on channel one and an acoustic guitar on channel two can be dialled in with completely different settings at the same time. This separation also lets a true stereo pair be matched precisely or two unrelated sources be tracked without compromise. Engineers running overdubs and stereo captures alike benefit from two discrete signal paths in one box.

Solid-State Topology with Transformer Tone

Pairing the vintage Lundahl input transformer with modern solid-state amplification, the ISA Two combines classic character with contemporary reliability and low distortion. Solid-state electronics use transistor-based gain stages rather than vacuum tubes, delivering consistent performance, instant warm-up, and long service life. This hybrid approach keeps the harmonic richness of the transformer while ensuring the preamp measures cleanly across its full gain range. Working professionals gain a preamp that sounds like a classic yet behaves like a dependable modern tool.

Variable High-Pass Filter and Who It Suits

A smooth 18dB-per-octave high-pass filter, of the same design as the original ISA 110 module, sweeps continuously from 16Hz to 420Hz. Filtering low frequencies at the input removes rumble, thumps, and plosive energy before they waste headroom in the converter or the mix. Setting the corner just below a source's fundamental tightens the low end without thinning the tone. With two channels of heritage sound, DI inputs, and flexible routing in a single rack space, the ISA Two suits singer-songwriters, stereo-recording enthusiasts, and studios needing a compact reference front end.