Focusrite ISA C8X’s preamps aren’t its only impressive feature

£1,900, focusrite.com

Industry behemoth Focusrite can, so the story goes, trace its success back to one key event. Eager to find a better-sounding preamp and EQ for use in his AIR Studios, Sir George Martin approached the newly-formed Focusrite in 1985 for a solution. He chose this unknown startup for a very good reason: Rupert Neve was the company’s founder and chief engineer. What resulted was the ISA 110, a transformer-coupled mic/line preamp and EQ module that proved so popular it pushed Focusrite onto the path that’s seen it rise to one of the biggest and most respected players in the industry.

Nowadays, Focusrite is just as well known for its Scarlett and Clarett audio interface lines, and it seems obvious that it should combine this expertise with its still-world-class ISA preamp design. This has finally happened with the launch of the ISA C8X.

What inputs and outputs does the Focusrite ISA C8X provide?

Shifting away from the red shades of Scarlett and Clarett, Focusrite has fronted the C8X’s rackmount 2U enclosure with a blue anodised panel liberally adorned with buttons, meters, and soft amber backlighting. The blue is much deeper and richer than the Novation-style blue shown on the Focusrite’s website (and the press shots here). The backlighting, reminiscent of glowing vacuum tubes, adds a delicious retro-tinged garnish atop the sharp contemporary lines of the fascia. It’s an exceptionally stylish thing!

Packed inside this handsome exterior is an impressive feature set. Each of the eight analogue mic/line inputs feature both XLR and balanced jack sockets on the rear panel, so you can connect both in an installation then switch between them via the control panel or Focusrite Control 2 (FC2) software. The first two channels can also handle high impedance instrument inputs via convenient front-facing jacks and, located between these, there’s a tiny hole behind in which lies a built-in talkback mic.

This generous output count ensures plenty of flexibility when hooking up outboard processors and routing any of the system’s six internal mixes to different performers or zones. They can also be assigned to any of C8X’s three monitor groups, switched from the unit’s fascia or the FC2 software, and these groups can be anything from two-channel stereo to 7.1.4 surround. Better still, output pairs can be included in multiple monitor groups so, for example, your main left/right stereo monitors can also be included as the front left/right pair in a surround configuration.

Input and output count can be expanded via digital I/O ports: one pair of coaxial in/out connectors and two pairs of optical ins/outs. The exact digital channel count depends on the unit’s sample rate and port configuration, but maxes-out at 16 channels at 44.1 and 48 kHz. Word clock input and output BNCs make it easy to integrate C8X with other digital gear, and I’m pleased to see a pair of old-school MIDI DINs nestled amongst the rear-panel connectors too.

Come on, tell us about these illustrious preamps!

Much to the chagrin of many an online commenter, only the first two channels are graced by ISA preamps, the remainder using the same preamp as found in many of Focusrite’s 4th generation Scarlett interfaces. I get the disappointment, but putting eight ISA pres into C8X would have pushed the price to at least the £5k mark, and the commentariat would instead decry the steep asking price. Besides, Focusrite sells digital output boards for its line of standalone ISA preamps, allowing them to integrate easily with C8X (or indeed many other interfaces), so there’s no problem adding additional ISA pres if you want.

There’s nothing inherently wrong with the non-ISA preamps (Focusrite calls them ‘modern-style’ preamps). They give a clean, well-balanced sound, a healthy 69dB of gain, and feature an Air mode presence peak and variable Drive setting, both aimed at making the preamp sound more console-like.

That said, the contrast between the ‘modern-style’ and ISA pres is immense – the latter are, after all, the real deal, right down to the genuine Lundahl LL1538 transformers, and so exude most of the qualities of the revered original. Low ends are rich and balanced. Mids are detailed and exquisitely defined, and the top end shines and sparkles yet manages to soften and sweeten any hint of harshness. And if the tonal balance and response isn’t quite right, a choice of four input impedances (the original 110’s 1.4kΩ, along with 800Ω, 2.4kΩ and 7kΩ options) aids in matching the preamp to the mic and source. Similarly, the instrument input can switch between 400kΩ and 1.2MΩ for a warmer or brighter sound, respectively.

Adding to the ISA pres are two analogue circuits that can be enabled. The 430 Air option engages an inductor-based high shelf circuit taken directly from the ISA 430 MkII preamp, giving a boost to presence and high-frequency detail. Console engages a soft clipping circuit aimed at injecting some of the pleasing overdrive that can be squeezed from the original ISA 110 by pushing the input into the module’s output transformer, and keeping levels under control with the output Trim control. C8X’s Console mode does a reasonable job of emulating this effect without adding cost, but a genuine trim-controlled output transformer would have been nice to see.

The ISA channels also sport 75 Hz 18dB/octave high-pass filters for removing rumble and handling noise and—one of my favourite features—fully balanced insert points for patching in outboard processors prior to the signal hitting the digital converters.

Is the ISA C8X easy to use?

All configuration of input channels can be performed directly on the unit’s front panel, as can monitor control and group switching, and headphone volume levels. Deeper control—including setting up the six internal monitor mixes—is handled by the FC2 software, which itself can be remote controlled by the FC2 app running on an iThing or Android device.

C8X also features an auto-gain system that monitors a few seconds of input and then sets channel gains appropriately. I have yet to encounter an auto-gain that isn’t overly conservative, and C8X’s system is no different. Better results can be achieved by spending a few minutes to set gains manually, but I can see the benefit in some use-cases (a self-recording drummer springs to mind). Oh, and, C8X’s auto-gain only appears to work on mic and instrument inputs – I’m not sure why the line inputs don’t get a look-in!

Do those ISA pres make C8X worth the money?

The ISA preamps are clearly C8X’s unique selling point, and are without doubt the thing that will attract the most attention. This is right and proper because they sound incredible! But there’s more to C8X than just a pair of fancy preamps; the remaining six are good too, and Focusrite has packed the unit with all the pro-level features you’d expect from an interface at this price.

The ISA C8X is (just about) affordable enough for smaller studios, yet has the flexibility and expandability to serve as the hub of far larger studios and post-production facilities. And, to top things off, it looks so damned good!

Key Features

• USB 2.0 audio interface
• 2 analogue mic/line/instrument inputs equipped with genuine ISA preamps, 430 Air circuit, soft clipping circuit, high pass filter and balanced insert points
• Switchable impedance for ISA preamp mic and instrument inputs
• 6 analogue mic/line inputs equipped with Scalett-style preamps featuring Air and Drive
• 12 analogue balanced line outputs
• 2 independent headphone outputs
• 2 optical I/O pairs supporting ADAT/SMUX and S/PDIF
• 1 coaxial I/O pair for S/PDIF
• Up to 16 channels of digital I/O at 44.1 kHz/48 kHz (reducing to 8 channels at 88.4 kHz/96 kHz; no ADAT I/O above 96 kHz)
• Word clock in/out via BNC
• MIDI in/out via standard 5-pin DIN
• USB-C socket (USB-C to USB-C cable provided)
• Focusrite Control 2 app for iOS and Android allows remote control of hardware
• Includes Focusrite Hitmaker Expansion featuring plugins, sounds, tutorials and more
• Sonnox Oxford Reverb included and Sonnox bundle discounts