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 40 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. 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 front-panel inputs with High (2.4 MΩ) and Low (470 kΩ) impedance settings, 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. Specifications Mic input response Gain Range (Mic)0dB to 60dB in 10dB steps 20 dB of variable gain EIN (Mic)-126dB measured at 60dB of gain with 150 Ohm terminating impedance and 22Hz/22kHz band-pass filter Noise (Mic)Noise at output with unity gain (0 dB) and 22 Hz-22 kHz band pass filter-97 dBu Signal-To-Noise Ratio (Mic)106 dB relative to max headroom (9dBu) Frequency Response (Mic)At minimum gain (0 dB)-0.5dB down at 10Hz and -3dB down at 125kHz CMRR (Mic)98dB (Channel 1, 1kHz, maximum gain with 24 dBu input) Crosstalk Channel To Channel (Mic)With 10dB@1kHz input to chA, chB output =104dBrA. With 10dB@10kHz input to chA, chB output = 84dBrA Line input response Gain Range (Line)-20dB to 10dB in 10dB steps 20 dB of variable gain Input Impedance (Line)10 kO from 10 Hz to 200 kHz Total Harmonic Distortion Noise (Line)Measured with a 0 dBu input signal, and a 22 Hz-22 kHz band pass filter0.0001 Frequency Response (Line)At unity gain (0 dB)-0.3dB down at 10Hz and -3dB down at 200kHz Instrument input response Gain Range (Instrument)10dB to 40dB continuously variable Input Impedance (Instrument)High = greater than 1M Low =greater than 300k THD (Instrument)At minimum gain ( 10) High-pass filter Roll-Off18 dB per octave (3 pole filter) FrequencyFixed 75Hz measured at the 3dB down point
