Focusrite ISA One Analog Single Channel Preamp

The Focusrite Heritage Sound in a versatile, transportable package.

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.

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.

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 in a highly cost-effective and flexible package.

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 inputs 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 choose to upgrade your unit with an optional digital card that delivers the best A-D performance in its class, with a dynamic range of 118dB.

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.

SPECIFICATIONS

Mic Input Response

* Gain range = 0dB to 60dB in 10dB steps + 20 dB of variable gain

* Input Impedance, variable as follows: (Switched Impedance setting Equivalent Input Impedance at 1kHz)

Low = 600 Ohms

ISA110 = 1400 Ohms

Med = 2400 Ohms

High = 6800 Ohms

EIN (equivalent input noise) = -126dB measured at 60dB of gain with 150 Ohm terminating impedance and 22Hz/22kHz band-pass filter

* Noise at main output with gain at unity (0dB) = -97dBu measured with a 22Hz/22kHz band-pass filter

* Signal to noise ratio relative to max headroom (9dBu) = 106dB

* THD at medium gain (30dB) = 0.0009% measured with a 1kHz -20dBu input signal and with a 22Hz/22kHz band-pass filter

* Frequency response at minimum gain (0dB) = -0.5dB down at 10Hz and -3dB down at 125kHz

* Frequency response at maximum gain (60dB) = -3dB down at 16Hz and -3dB down 118kHz

* CMRR=98dB (Channel 1, 1kHz, maximum gain with +24 dBu input)

* Crosstalk Channel to Channel: with 10dB@1kHz input to chA, chB output =104dBrA. With 10dB@10kHz input to chA, chB output = 84dBrA

Line Input Response

* Gain range = -20dB to +10dB in 10dB steps + 20 dB of variable gain

* Input Impedance = 10kOhm from 10Hz to 200kHz

* Noise at main output with gain at unity (0dB) = -96dBu measured with a 22Hz/22kHz band-pass filter

* Signal to noise ratio relative to max headroom (24dBu)=120dB

* Signal to noise ratio relative to 0dBFS (+22dBu) = 118dB

* THD at unity gain (0dB) = 0.001% measured with a 0dBu input signal and with a 22Hz/22kHz band-pass filter

* Frequency Response at unity gain (0dB) = -0.3dB down at 10Hz and -3dB down at 200kHz

Instrument Input Response

* Gain range = 10dB to 40dB continuously variable

* Input Impedance:

High = greater than 1M

Low = greater than 300k

* Noise at minimum gain (+10dB) = -92dBu measured with a 22Hz/22kHz band-pass filter

* Noise at maximum gain (+40dB) = -62dBu measured with a 22Hz/22kHz band-pass filter

* THD at minimum gain (+10dB) = 0.001% measured with a 10dBu input signal and with a 22Hz/22kHz band-pass filter

* Frequency Response at 10dB gain with -10dB input = 10Hz-100kHz +/- 0.6dB

* THD at unity gain (0dB) = 0.001% measured with a 0dBu input signal and with a 22Hz/22kHz band-pass filter

* Frequency Response at unity gain (0dB) = -0.3dB down at 10Hz and -3dB down at 200kHz

Instrument Input Response

* Gain range = 10dB to 40dB continuously variable

* Input Impedance:

High = greater than 1M

Low = greater than 300k

* Noise at minimum gain (+10dB) = -92dBu measured with a 22Hz/22kHz band-pass filter

* Noise at maximum gain (+40dB) = -62dBu measured with a 22Hz/22kHz band-pass filter

* THD at minimum gain (+10dB) = 0.001% measured with a 10dBu input signal and with a 22Hz/22kHz band-pass filter

* Frequency Response at 10dB gain with -10dB input = 10Hz-100kHz +/- 0.6dB

* Frequency Response at 40dB gain with -40dB input = -2.5dB down at 10Hz and 0dB at 100kHz

High Pass Filter

* Roll off = 18dB per octave 3 pole filter

* Fixed Frequency 75Hz measured at the 3dB down point

Meters

* Moving coil (MC) meter is factory calibrated to 0VU = +4dBu with 1kHz sinewave. With the VU Cal button pressed the meter can be adjusted on the rear panel to allow 0VU to equal +10dBu to +26dBu with the centre detent being equal to +22dBu.

* Peak LED meters calibrated in the detent position for 0dBFS = +22dBu, calibration is adjustable on the rear panel to allow 0dBFS to equal +10dBu to +26dBu

* Routing for MC and Peak1 meter is after the HPF, pre insert send or switched post insert return. Peak2 is always pre ADC channel 2, which can be fed by external input or Instrument input.

* LED levels are as follows when peak calibration is set to center detent on the rear panel. (This is when using the internal ADC).

0 = +22dBu

-2 = +20dBu

-6 = +16dBu

-12 = +10dBu

-18 = +4dBu

-42 = -20dBu

FRONT AND REAR CONNECTIVITY

Analogue Channel Inputs:

* Mic input: XLR x 1

* Line input: XLR x 1 and TRS x1

* Instrument input TRS Jack: XLR x 1

* External ADC input: TRS Jack x 1

* Return: TRS Jack x 1

Analogue Channel Outputs:

* Send: TRS Jack x 1

* Balanced line output: XLR x 1

* DI output: XLR x 1

* DI through: TS Jack x 1

Analogue Channel Additional I/O:

* Cue mix left input: TRS Jack x 1

* Cue mix right input: TRS Jack x 1

* Headphones output: 1/4" TRS Jack x 1

* Weight: 3.9kg / 8.6lbs

* Dimensions: 220mm (W) x 104mm (H) x 254 - 290mm (D - top to bottom) / 8.66" (W) x 4.1" (H) x 10" - 11.4" (D - top to bottom)