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The Focusrite ISA One provides a lot of power in an unusual package.
The Focusrite ISA One provides a lot of power in an unusual package.

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Focusrite ISA One
By Paul Vnuk Jr.
Date: August 2009

ISA stands for Input Signal Amplifier. The ISA One is Focusrite's latest addition to the ISA line of mic preamps and channel strips, all of which have their origins in the company's high-end Forte console of the late '80s. Previously only available in multi-channel configurations, the ISA One-as the name implies-marks the first appearance of this microphone pre amp in a single, non-channel-strip configuration.

Not content to be just a mic pre, though, the ISA One packs a healthy number of features under its hood that include: impedance switching, independent DI, basic DAW monitoring, and full-featured metering. There is also an option to add analog-to-digital conversion via an expansion board (not covered in this review).

A case of style

With a slanted blue and gray faceplate and classic yellow knobs, the ISA One fits in perfectly with the rest of the ISA line. Designed as a tabletop unit rather than a rackmount, it is rugged and includes a stylish leather handle and a sturdy custom flight case for easy relocation.

"MsoPlainText">Plethora of control

In addition to standard mic pre specs such as +48v Phantom power, phase switching, and an 18 dB @ 75 Hz highpass filter, The ISA One's front panel also includes:

• A switchable insert point (for inserting your favorite eq or compressor)

• A dual gain structure with a maximum of 60 dB of input (perfect for ribbons and dynamic mics)

• Three input choices (mic, line or instrument)

• An independent high or low-Z 1/4" instrument DI (with an amp thru)

• Headphone monitoring with cue mix

• 3-stage metering with a full-size, old-school analog VU meter, 6-step LED input meter, and a 6-step DI input meter.


On the back there are ten inputs and outputs, a lot for a mic pre. There are:

• Choice of XLR mic or 1/4" and XLR balanced line inputs

• 1/4" balanced send and return for the channel insert

• An additional 1/4" external input

• A 1/4" cue mix in and out

• Balanced XLR outputs for both the main and DI outs

as well as

• VU & Peak meter attenuation knobs

• Power switch

• 3-prong power cable socket for the internal power transformer (i.e., no wall warts or external power supply).

The Pre and Instrument inputs

Nifty extras aside, the ISA One's main reason for being is as a microphone preamp, and on vocals, electric guitar, acoustic guitar, drums and percussion (that's what I tried it on) it simply sounded great. I would call the ISA One "neutral and clean with a touch of punch". The word that comes to mind is classic, but do not translate that to mean vintage...

The ISA One is part of a newer trend I have noticed where mic pres are neither thick and vibey nor ultra real and crystal clear... instead we seeing mic pres that sound and function like traditional console pres, which stack well and stay out of the way. This describes the ISA One well, because in essence it is a direct descendant of the Rupert Neve designed Focusrite ISA preamps of the past.

The ISA One has headroom and input gain for days. Ribbon mics and dynamics like Shure's SM7 & SM57 work well with this unit.

My favorite extra feature on this unit is the selectable impedance switching. I have one other preamp in my collection with impedance switching, but it only offers two choices, while the ISA offers four: High, Medium, ISA 110 (the classic original British sound of this pre) and Low. Changing a preamp's impedance changes the sound of the microphone, making it a really cool way to tailor your sound.

Having a DI, line or even a Hi-Z input for instruments is nothing new on mic pres, but offering a choice of all three, especially when the DI can remain independent of the mic channel, is. This makes the ISA One a two-channel unit in some instances.

Monitor with your eyes...

Oddly enough, basic input metering is actually quite rare on mic pres other than an occasional signal/clip LED. The ISA gives you 6-stage LED metering set to digital calibration for most DAWs, a second 6-stage LED for the independent DI, and rarer still, a full-on VU meter, calibrated for analog for true "old school" recording... in other words, hitting the red!

...and monitor with your ears

The ISA One features a headphone output with the ability to accept a cue mix from your DAW or recorder, allowing you to monitor both the mix and your performance when tracking.

Both the DI and mic pre remain independent so you can hear both in your ears, handy if you are singing and playing at the same time for example. However, I would view this is a bonus feature and not a selling point, as there is no way to alter your mix levels or blend on the unit itself.


To my ears the ISA One more than held its own against the API 512s I had in my studio at the time, as well as my beloved Chandler TG2s.

With many professional single-channel mic pres falling in the $700-$1200 range, the competition is fierce. However, at $799.99 street the ISA One falls nicely in that price range, and holds its own sonically with all of them.

Whether or not it is right for you and your studio will rest on two things: sonic taste and feature set. With that in mind, it sounds great, and its multiple impedance choices, stand-alone DI, monitoring, and real VU meter give it a nice edge.

Price: $799.99 street

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