Focusrite ISA One Classic Single Channel Mic Pre

Classic vintage microphone preamplifier at a groundbreaking price.

The ISA One microphone preamplifier delivers Focusrite’s prestigious ISA transformer-based preamp in a rugged and portable chassis, at a groundbreaking price. ISA One features the classic vintage microphone preamplifier topology from the original ISA 110 module, including the Lundahl L1538 transformer and bespoke zobel network. (The original 110 pre amp formed the cornerstone of each channel of Focusrite’s legendary Forte console.)

The pre-amp is complemented by a line input (XLR and TRS Jack) and an independent DI 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 DI makes the ISA One ideal both for engineers wishing to blend a DI’d guitar signal with a mic’d guitar cabinet, and for demanding performers who require a single classic solution for both guitar and vocals.

A variable impedance circuit has been added, allowing the user to switch between four carefully selected input impedance settings. In addition to the original ISA 110 impedance, three further impedance settings allow perfect matching, or creative mismatching of the pre amp with any microphone. ISA One also features an insert point, should the need arise to place extra processing between the preamp or DI, and the optional converter. Phantom power, phase reverse and a 75Hz, 18dB/octave high-pass filter are also available from the angled front fascia.

Independent input metering for both channels is provided in the form of a moving-coil VU meter with variable calibration to suit analog and digital recording media, alongside two six-LED peak meters; inputs can be metered either pre- or post-insert. The meter calibrations utilize all the same reference points as Digidesign’s Pro Tools HD system, allowing effortless line-up.

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.

An optional state-of-the-art stereo A/D converter is also available (the same card as used with the ISA430 Mk II), embodying cutting-edge conversion technology seated within Focusrite’s custom analogue circuitry. This optional card can be retrofitted at any time and provides two channels of 24 bit/192kHz A-D conversion with a dynamic range of 119dB.

The ISA microphone preamplifier was first introduced back in 1985. This transformer-based preamplifier formed the first half of the ISA 110 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.

The ISA microphone preamplifier went on to form the cornerstone of all ISA and RED Focusrite products. The topology has never changed, except for the addition of a variable impedance circuit, allowing ISA users to either perfectly match the preamp with any microphone, thus maximizing level, or to use different settings creatively to shape the sound of the microphone being used. The original ISA 110 setting was supplemented by three further impedance settings.

The Focusrite preamp is renowned for its transparency, but there’s also that subtle warmth that transformer core saturation contributes. This seeming contradiction of warmth plus beautifully open, unrestricted high frequencies, is a classic hallmark of the mid ’80s Focusrite designs.

With processors whose bandwidth is strictly limited to the audible (20Hz to 20kHz) bandwidth alone, significant roll-off can still occur, affecting the higher audible frequencies of the signal. Therefore, in order to capture every subtle nuance, exactly as it occurs whilst avoiding any roll-off, the preamp must operate over a far greater bandwidth. The extremely broad frequency response of Focusrite preamps – close to 200kHz at the top end – guarantees accurate phase response across the much narrower range of human hearing, the roll-off point being moved entirely outside of the audible hearing range.

•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.

•Switchable Impedance – Choose one of four carefully selected input impedances, including the original ISA 110 setting, to suit any microphone.

•Optional Stereo 192kHz ADC – This optional card embodies cutting-edge conversion technology, incorporating Focusrite analog circuitry to deliver the best A/D performance in its class (Dynamic range of 119dB).

•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 mix 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.

NOTE: The DI and the ADC (digital conversion card) are not included and are sold separately. This optional state-of-the-art stereo A-D converter (the same card as used with the ISA430 Mk II), embodies the cutting-edge conversion technology seated within Focusrite’s custom analogue circuitry. This optional card can be retrofitted at any time and provides two channels of 24 bit/192kHz A-D conversion with a dynamic range of 119dB.