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Focusrite ISA One

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Quick Overview

Featuring a rugged, portable all-metal enclosure, the ISA One combines the classic Focusrite microphone preamp with a flexible, independent DI channel and optional 192kHz precision A/D conversion.

The Focusrite Heritage Sound - in a versatile, transportable package

Back in the mid-1980s, Sir George Martin commissioned console design legend Rupert Neve to build a series of new, ‘no compromise’ console modules for AIR studios. They were an enormous hit and formed the basis of the Focusrite Studio Console, widely regarded as the best-sounding analogue recording console of all time. Today, the descendants of those modules are used in leading studios around the world, and their sought-after Focusrite Heritage Sound lies behind thousands of hit records. Today’s ISA Range from Focusrite puts the classic sound of Focusrite into your own studio or live performance.


Classic Focusrite transformer-based mic preamplifier

At the heart of the ISA range is the microphone preamplifier with its Lundahl input transformer – essentially the same circuit, based on the original ISA110, that has been used for 30 years in successive Focusrite designs. The input transformer imparts a special character to the sound that can’t be truly emulated in any other way: inseparable from the microphone itself, the transformer input stage is ideal for use with classic microphones. But this mic pre has a twist the original didn’t have, which makes it far more versatile: four carefully-selected impedances allow you to match microphone to input in different ways. Bring out the character of a classic mic or emphasise a special feature, or go for a totally transparent, modern sound – it’s up to you.

Independent direct input

Whether you’re an artist, engineer or producer, you’ll appreciate the versatility of the ISA One, with its front-panel DI input. The DI includes low/high impedance switching and an amplifier output, and its own feed to the optional A/D converter and separate rear-panel XLR output



Key Features

ISA series transformer-based preamplifier

Encased in a rugged and portable chassis, ISA One offers the classic Focusrite microphone preamplifier at its lowest cost to date.

Flexible independent DI channel

ISA One is ideal for both engineers and demanding performers alike, featuring independent gain control, an output for routing to an amp, an independent XLR output on the rear and routing to the optional A-D converter.

Switchable impedance

Choose one of four carefully selected input impedances, including the original ISA110 setting, to suit any microphone.

Headphone output with volume control

ISA One can feed either a sum of the two input to the headphones output, or an external stereo cue mix (such as a stereo feed from an interface) via two TRS jack inputs on the rear of the unit.

Dedicated insert point

Allows you to place extra processing between the preamplifier or DI and the optional converter, such as an EQ or compressor.

Optional stereo 192kHz A-D converter

You can chose to upgrade your unit with an optional digital card that delivers the best A-D performance in its class (dynamic range of 118dB). Alternatively, the ISA One Digital comes with the A-D converter as standard.

Lundahl LL1538 Input Transformer

The original mic transformer used in the original Red modules helps to provide the unique sound and performance of this groundbreaking design.

Backlit VU meter with variable calibration

ISA One has a moving coil VU meter with variable calibration to suit analogue and digital recording media, alongside two six-LED peak meters; inputs can be metered either pre- or post-insert.


Analog inputs

  • XLR mic input
  • An XLR line and a balanced TRS line input
  • XLR input with balanced TRS instruments
  • External sensor input with balanced jack
  • Return with balanced TRS

Analog outputs

  • Send with balanced jack
  • Balanced XLR line output
  • XLR DI output
  • Klinke-OF-Through

Additional analog inputs and outputs

  • Cue Mix input (left) with balanced jack
  • Cue Mix input (right) with balanced jack
  • Headphone output with 6.3 mm jack symmetric

Mic input

Gain range0 dB to 60 dB in 10 dB steps and +20 dB adjustable gain
Input ImpedanceConnected impedances. Equivalents of input impedance at 1 kHzLow = 600 Ohm
ISA110 = 1.400 Ohm
Med = 2.400 Ohm
High = 6.800 Ohm
ON (Equivalentes input noise)-126 DB, measured at 60 dB gain with 150 Ohm impedance and 22 Hz / 22 kHz bandpass filter
MurmurOutput noise with 0 dB gain and 22 Hz / 22 kHz bandpass filter-97 DBu
Gerauschspannungsabstand (SNR)106 dB, relative to the maximum headroom (9 dBu)
Total-Harmonic-Distortion + RauschenMeasured at average gain (30 dB) at 1 kHz -20 dBu input signal and 22 Hz / 22 kHz bandpass filter<0.0009%
Frequency responseAt minimum gain (0 dB)-0.5 DB at 10 Hz and -3 dB at 125 kHz
 At maximum gain (60 dB)-3 DB at 16 Hz and -3 dB at 118 kHz
CMRR (Common Mode Rejection Ratio)98 dB (Channel 1, 1 kHz, maximum gain with +24 dBu input)
However, channel-to-channel crosstalkWith 10 dB @ 1 kHz input to channel A, channel B output = 104 dbra. With 10 dB @ 10 kHz input to channel A, channel B output = 84 dbra

Line input

Gain range-20 DB to 60 dB in 10 dB steps and +20 dB adjustable gain
Input Impedance10 kO from 10 Hz to 200 kHz
NoiseNoise Main.Ausgang with gain (0 dB) measured by 50 O source impedance and 22 Hz - 22 kHz bandpass filter-96 DBu
Gerauschspannungsabstand SNRGemessen it 22 Hz - 22 kHz Bandpass-Filter120 dB relative to the maximum headroom (24 dBu) 
118 dB relative to 0 dBFS (+22 dBu)
THD and noiseMeasured with 0 dB input signal and 22 Hz-22 kHz bandpass filter0,0001 %
Frequency responseAt 0 dB gain-0.3 DB at 10 Hz and -3 dB at 200 kHz

Instrument input

Gain rangeAdjustable from 10 dB to 40 dB
Input ImpedanceHigh = grˆfler als 1 M
Low =grafler als 300 k
MurmurMeasured with 22 Hz-22 kHz bandpass filterMinimum Gain (+10 dB): -92 dBu 
Maximum Gain (+ 40dB): -62 dBu
THDAt minimum gain (+10)
Frequency responseAt minimum gain (+10 dB)-10 DB input: 10 Hz - 100 kHz +/- 0.6 dB
 At maximum gain (+40 dB)-40 DB Input: -2.5 dB at 10 Hz and 100 kHz 0 dB


Coil-level display (MC)Factory calibrated to 0 VU = +4 dBu at 1 kHz sine wave. In gedr¸cktem VU Cal switch on the back of the display can be changed ‰ ge, so 0 VU +10 dBu to +26 dBu match.The central point corresponds to +22 dBu.
Peak-LED-AnzeigeCalibrated in the position for 0 dBFS = +22 dBu. The cali- bration can be changed on the back ge ‰, so that 0 dBFS correspond dBu to +26 dBu equal to +10
MC and Peak1 display can be tapped after the high-pass filter, either before the insert send or behind the insert return. Peak2 is always picked up before the A / D converter channel 2, which is fed from the external input or the instrument input.
LED levelAs follows when the peak calibration is on the back in a central position. (When using the internal A / D converter).0 = +22 dBu 
-2 = +20 dBu 
-6 = +16 dBu 
-12 = +10 dBu 
-18 = +4 dBu 
-42 = -20 dBu
Frequency responseAt minimum gain (+10 dB)-10 DB input: 10 Hz - 100 kHz +/- 0.6 dB
 At maximum gain (+40 dB)-40 DB Input: -2.5 dB at 10 Hz and 0 dB at 100 kHz


Roll-Off18 dB per octave (3-pole filter)
Frequency75 Hz fixed, at 3 dB down point

Weight and dimensions

B x T x H220 mm (W) x 104 mm (H) x 254-290 mm (T - top to bottom)
Weight3,9 kg