ISA One

Description

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 gives a special character to the sound that cannot truly be emulated in any other way: inseparable from the microphone itself, the transformer-based input stage is ideal for use with classic microphones. However, this mic preamp has a twist that the original did not, making it much more versatile: four carefully selected impedance settings allow you to match the microphone to the input in different ways. Bring out the character of a classic mic, highlight a unique feature, or opt for a completely transparent and modern sound—it's your choice.

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

Key Features:

• Transformer-based ISA Series Preamplifier - Housed in a robust and portable chassis, the ISA One offers Focusrite’s classic microphone preamp at its lowest cost to date.

• Independent and Flexible DI Channel - ISA One is perfect for both engineers and demanding performers, featuring front-panel inputs with High (2.4 MΩ) and Low (470 kΩ) impedance settings, independent gain control, an amplifier output, an independent rear-panel XLR output, and routing to an optional A-D converter.

• Switchable Impedance - Choose from four carefully selected input impedances, including the original ISA110 setting, to suit any microphone.

• Headphone Output with Volume Control - ISA One can drive the headphone output with the sum of both inputs or a mix of an external stereo source (such as a stereo input from an interface) via two TRS jack inputs on the back of the unit.

• Dedicated Insert Point - Allows additional processing between the preamp or DI and the optional converter, such as an equalizer or compressor.

• Optional 192 kHz Stereo A-D Converter - Upgrade your unit with an optional digital card offering best-in-class A-D performance (118 dB dynamic range). Alternatively, the ISA One Digital includes the A-D converter as standard.

• Lundahl LL1538 Input Transformer - The original mic transformer used in the classic Red modules contributes to the unique sound and performance of this pioneering design.

• Backlit VU Meter with Variable Calibration - ISA One features a moving-coil VU meter with variable calibration to match both analog and digital recording formats, along with two six-LED peak meters. Inputs can be metered pre- or post-insert.

Detailed Specifications

Microphone Input Response

• Gain Range (Microphone): 0 dB to 60 dB in 10 dB steps, 20 dB variable gain
• EIN (Microphone): -126 dB measured at 60 dB gain with 150Ω termination impedance and 22Hz/22kHz bandpass filter
• Noise (Microphone): Output noise with unity gain (0 dB) and 22 Hz-22 kHz bandpass filter: -97 dBu
• Signal-to-Noise Ratio (Microphone): 106 dB relative to maximum range (9 dBu)
• Frequency Response (Microphone): At minimum gain (0 dB): -0.5 dB at 10 Hz and -3 dB at 125 kHz
• CMRR (Microphone): 98 dB (Channel 1, 1 kHz, maximum gain with 24 dBu input)
• Channel-to-Channel Crosstalk (Microphone):
  • With 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 Response

• Gain Range (Line): -20 dB to 10 dB in 10 dB steps, 20 dB variable gain
• Input Impedance (Line): 10 kΩ from 10 Hz to 200 kHz
• Total Harmonic Distortion + Noise (Line): Measured with 0 dBu input signal and 22 Hz-22 kHz bandpass filter: 0.0001
• Frequency Response (Line): With unity gain (0 dB): -0.3 dB at 10 Hz and -3 dB at 200 kHz

Instrument Input Response

• Gain Range (Instrument): 10 dB to 40 dB continuously variable
• Input Impedance (Instrument): High = greater than 1M Low = greater than 300k
• THD (Instrument): At minimum gain (10)

High-Pass Filter

• Roll-Off: 18 dB per octave (3-pole filter)
• Frequency: Fixed at 75 Hz, measured at -3 dB cutoff point