Focusrite Clarett+ 8Pre

Necessity may be the mother of invention, but a switch to Cirrus Logic converters has also significantly improved Focusrite's Clarett+ audio interfaces...

The well‑known UK pro‑audio manufacturers Focusrite introduced their original Clarett suite of Thunderbolt‑connected interfaces in 2015, aimed at high‑end project‑studio owners seeking really top‑spec performance. Three years later, updated models were shown at NAMM 2018, re‑engineered with the ubiquitous USB interface format, and the resulting 2Pre, 4Pre and 8Pre models quickly became enormously popular. One notable attraction of the whole range was that even the smallest model could be expanded via ADAT inputs to accept eight additional analogue channels, ideally from the matching Clarett Octopre mic preamp/converter. My colleague Sam Inglis reviewed both the original Clarett 8Pre‑Thunderbolt (in the October 2015 edition), and the Clarett 8Pre‑USB (in the March 2018 edition of Sound On Sound).

However, last year Focusrite faced a big problem with its Clarett USB range! As explained in the ‘Chip Crisis’ article published in the Sound On Sound September 2021 edition, a huge fire last year all but obliterated the Japanese factory of Asahi Kasei Microsystems — AKM being one of the major suppliers of high‑quality A‑D and D‑A converter and digital interface chips to much of the pro‑audio industry.

Needless to say, Focusrite’s Clarett range employed AKM converter chips extensively, and without a consistent supply of converter chips Focusrite can’t build audio interfaces. So the company was effectively forced into redesigning the Clarett product range to use alternative brands of converters — something which is far from a trivial task!

However, having been handed life’s sour lemons Focusrite decided to make tasty lemonade by taking the opportunity to build upon and enhance the Clarrett range’s already impressive performance. New high‑end converters were selected from a well‑respected manufacturer called Cirrus Logic; the A‑Ds are CS‑5381 chips with an advanced multi‑bit delta‑sigma architecture and 24‑bit output, while the D‑As are CS‑43198 converters, which use 32‑bit oversampled multi‑bit modulators. Focusrite’s engineers have also meticulously designed the associated output filtering parameters for optimal performance. The technical improvements brought about by this substantial redesign are such that Focusrite thought the product name warranted enhancement too, hence Clarett+.

The most obvious benefits of the Clarett+ redesign are greater dynamic range and lower distortion figures across the board. Of course, the original Clarett was hardly a slouch in this regard, but the improvements are not only measurable but audible too, especially when working in challenging conditions. Given how good modern digital equipment already is, Focusrite’s update actually represents quite a significant step forward in engineering terms.

Flagship Overview

I was provided with the flagship model for this review, the Clarett+ 8Pre, which is described as “a powerful studio‑grade 18‑in/20‑out audio interface”. Aside from the incremental performance lift afforded by its technical redesign, the Clarett+ 8Pre is pretty much identical to the preceding model and I’d urge you to read Sam’s reviews mentioned above for the full ‘SP’. However, key practical points to note are that the unit is mains‑powered via an internal switch‑mode PSU (accepting 100‑240V AC through a standard IEC inlet), and it connects to the host computer via a USB‑C connector on the rear panel (USB C‑C and USB C‑A cables are included in the box).

Its eight premium preamps are all connected via ‘combi’ XLRs for mic/line inputs, with six on the rear panel and two more on the front panel (which also have high‑impedance JFET instrument input modes). Ten analogue line outputs are provided on TRS sockets at the rear, two being dedicated as monitor outputs, while a pair of independent stereo headphone outputs is available on the front. Ten channels of digital connectivity in and out are provided through stereo S/PDIF (RCA‑phono or optical) and ADAT (assuming the ports aren’t being used for S/PDIF). The ADAT interface provides eight channels at base sample rates, of course, and proportionally fewer at higher sample rates using the S/MUX protocol. A pair of DIN sockets is included for old‑school MIDI in and out, while a word‑clock BNC output allows synchronisation of other connected digital equipment (such as the Clarett Octopre as an input expander).

The transformerless preamp design claims ISA110 heritage, but while the gain stage is based around an NE5532 op‑amp just like the ISA110, the original Lundahl input transformer has been replaced with an electronically‑balanced discrete transistor input stage. Nevertheless, the design achieves remarkably low noise (specified as an EIN of ‑129dBu A‑weighted) and has excellent headroom margins — the maximum mic input level is a very generous +18dBu, while the line input can take +26dB before complaining, and even the instrument inputs can cope with +15dBu. So there shouldn’t be any problems with either high or low source levels, although the maximum channel gain is 57dB, which precludes working directly with really quiet sources.

Focusrite have also retained the “all‑analogue Air EQ” feature, which can be applied to individual preamp channels. When activated, the high frequencies are boosted in two stages by +4dB overall to bestow crisp transients, enhance presence‑range clarity and, yes, to add ‘air’ to whatever you’re recording. It is quite an alluring effect on vocals and acoustic guitars, in particular, but one which should probably be used with cautious discretion, I think — you really can have too much of a good thing! Interestingly, activating the Air option also reduces the microphone preamps’ input impedance from 6.2kΩ to 2.2kΩ — but while that might alter the tonality of some dynamic mics slightly, any changes would be thoroughly swamped by the Air effect anyway!

The unit’s front panel carries physical controls for phantom power (switchable in two groups of channels 1‑4 and 5‑8), preamp channel gains, headphone volumes, and the dedicated monitor section (with its own volume control and dim/mute buttons). Further configuration is via the elegant Focusrite Control app (for PC, Mac and iOS devices), which provides remote access to some relay‑switched preamp settings (line/instrument mode on channels 1‑2, and the Air EQ on all channels), as well as configuring the internal signal routing between the USB channels and the physical inputs and outputs to create monitor mixes, selecting the internal sample rate, and so forth.

Bench Tests

On the A‑D side of things, the new Clarett+’s dynamic range figure remains much the same as the previous model. My own test bench measurements using an Audio Precision system gave an AES17 dynamic range measurement of 117.7dB (A‑wtd), which conforms to the published specification of 118dB. I’m not sure why, but the Clarett+ 2Pre is claimed to achieve a slightly better result than its predecessor at 119dB (A‑wtd).

However, while the A‑D’s dynamic range figure is essentially unchanged, the distortion and noise performance has been improved, with the THD+N parameter being reduced to ‑110.1dB (or 0.0003 percent) from ‑107dB (0.0004 percent) in the previous generation product. That translates in the real world to a marginally clearer, cleaner, and more transparent source recording, especially if tracking with generous headroom margins.

The new Clarett+ is the same but better, both measurably and audibly, and it stands up extremely well against seriously high‑end equipment.

It is the Clarett+’s line outputs which show the greatest improvement, though, with a claimed 6dB improvement in dynamic range combined with 3dB lower distortion. The 8Pre’s new converters are aligned such that 0dBFS from the DAW or digital inputs corresponds to +18dBu at the analogue outputs, and my bench tests gave an AES17 dynamic range figure of 123.9dB (A‑weighted) for the D‑A stage. This corresponds to Focusrite’s published specification of 124dB and is nearly 6dB better than the previous model’s 118dB (A‑weighted).

The THD+N figure for the D‑A measured ‑106.1dB (the published spec is ‑106dB), which is also a very worthwhile improvement over the previous model’s ‑103dB. The headphone outputs have also gained 3dB more dynamic range and 3dB lower THD, too — all of which means lower noise and more pristine low‑level details in reverb tails and room atmospheres.

To provide some real‑world context here, an AES17 dynamic range figure of 124dB (A‑weighted) — which the Clarett+ scores for its balanced line outputs — means it rates in the top five of all the interfaces and converters I’ve measured to date, alongside high‑end products like the Benchmark DAC2 HGC, and outperforms RME’s ADI‑2 Pro. The 118/119dB (A‑weighted) figure for the A‑D conversion places the Clarett+ on the borderline of the top 10, rubbing shoulders with classy products like Focusrite’s own RedNet and ISA digital card, Crookwood’s M1 mastering console, Prism’s Titan/Lyra interfaces, and Cranborne’s R500 rack. So these really are very impressive specifications by anyone’s standards, let alone for a moderately priced project studio interface.

Clarett+ Conclusion

Although the need to update the Clarett range was forced by circumstances beyond Focusrite’s control, the results are impressive and well worthwhile. The new Clarett+ is the same but better, both measurably and audibly, and it stands up extremely well against seriously high‑end equipment.