Focusrite ISA One Classic Analogue Single-Channel Pre-Amp

Full Description

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History

The ISA microphone pre-amplifier was first introduced back in 1985. This transformer-based pre-amplifier formed the first half of the ISA110 mic-pre and EQ module on Focusrite's critically acclaimed Forte console. This console, and the later Studio console were hailed by many as the finest sounding consoles ever built.

Connectivity

The preamp is complemented by a line input and an independent D.I. channel, complete with dedicated gain control, active or passive impedance switch, a TRS Jack output for routing to an amp and an independent XLR output on the rear. This flexible independent D.I. makes the ISA One ideal both for engineers wishing to blend a D.I.'d guitar signal with a mic'd guitar cabinet, and for demanding performers who require a single classic solution for both guitar and vocals.

Variable Impedance Circuit

A variable impedance circuit has been added, allowing the user to switch between four carefully selected input impedance settings. In addition to the original ISA110 impedance, three further impedance settings allow perfect matching, or creative mismatching of the preamp with any microphone. ISA One also features an insert point, should the need arise to place extra processing between the preamp or D.I. and the optional converter. Phantom power, phase reverse and a 75Hz, 18dB/octave high-pass filter are also available from the angled front fascia.

Input Metering

Independent input metering for both channels is provided in the form of 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. The meter calibrations utilise all the same reference points as Avid's Pro Tools HD system, allowing effortless line-up.

Headphone Output

ISA One's headphone output features a dedicated volume control, which delivers an external stereo cue mix (a simple click track or a stereo mix feed from an interface or a live console) fed to the headphones via two TRS jack inputs on the rear of the unit.

Features

• Rugged and portable transformer-based pre amp
• Classic ISA mic preamp design with Lundahl LL1538 input transformer
• Line input (XLR and TRS Jack)
• Independent D.I. channel
• Insert Point
• VU Meter
• Six Led Peak meters
• Headphone out with dedicated volume control
• Optional Stereo A/D Converter provides two channels of 24 bit/192kHz A-D conversion with a dynamic range of 119dB.

Specifications

Mic Input Response

• Gain Range (Mic): 0dB - 60dB in 10dB Steps 20 dB of Variable Gain
• EIN (Mic): -126dB Measured @ 60dB of Gain w/150 Ohm Terminating Impedance & 22Hz/22kHz Band-Pass Filter
• Noise (Mic): Noise @ Output w/Unity Gain (0 dB) & 22 Hz-22 kHz Band Pass Filter-97 dBu
• Signal-to-Noise Ratio (Mic): 106 dB Relative to Max Headroom (9dBu)
• Frequency Response (Mic): @ Minimum Gain (0 dB)-0.5dB Down @ 10Hz & -3dB Down @ 125kHz
• CMRR (Mic): 98dB (Channel 1, 1kHz, Maximum Gain w/24 dBu Input)
• Crosstalk Channel to Channel (Mic): 10dB@1kHz Input to chA, chB Output =104dBrA. 10dB@10kHz Input to chA, chB Output = 84dBrA

Line Input Response

• Gain Range (Line): -20dB - 10dB in 10dB Steps 20 dB of Variable Gain
• Input Impedance (Line): 10 kO from 10 Hz - 200 kHz
• Total Harmonic Distortion Noise (Line): Measured w/a 0 dBu Input Signal, & a 22 Hz-22 kHz Band Pass Filter0.0001
• Frequency Response (Line): @ Unity Gain (0 dB)-0.3dB Down @ 10Hz & -3dB Down @ 200kHz

Instrument Input Response

• Gain Range (Instrument): 10dB - 40dB 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 75Hz Measured @ the 3dB Down Point

Dimensions

• Width: 220mm
• Depth: 254 - 290mm
• Height: 104mm
• Weight: 3.9 kg (8.6 lbs)