Solid State Logic: Fusion Master Processor

Solid State Logic has dominated the analog mixing console world for rock, pop, and R&B records for over three decades, and while DAWs have mostly taken over as production and mixing environments, SSL has been expanding into digital consoles for broadcasting and live sound. SSL also produces a line of rackmount and modular analog processors to please engineers and producers who crave the traditional SSL flavor. Recently SSL released Fusion, a well-thought-out and truly unique analog mixing and mastering processor. In just a two rack space unit analog chassis, Fusion incorporates five individual analog processing sections that effectively manipulate flavor, tone and color. Simple yet effective controls apply EQ, harmonics and saturation, frequency based compression, and stereo image processing. Additionally, it allows for several different internal signal flow paths and includes an external analog insert point.

Fusion is designed to be used as a stereo mastering processor or as an insert on an instrument or bus and easily handles levels up to +27 dBu, which is a few dB higher than even most pro analog to digital converters can handle. Before the processors are applied, the signal path of the Fusion provides an impressive frequency response of 5 Hz to over 180 kHz. Getting to know this unit takes time, as all five processors interact to some degree with each other. Finding the appropriate gain structure and sweet spot for each processing section can take some experimentation. SSL allowed me several weeks to get to know Fusion while I was mixing and mastering projects across a wide range of musical styles.

The input trim control provides ± 12 dB of swing and sets the initial signal level. Next comes the high-pass filter with frequency choices of 30 Hz, 40 Hz, and 50 Hz or Off. In use I found the 18 dB/octave filter to sound transparent and subtle, without noticeable phase shift in the higher frequencies. Do not expect this filter to sound nearly as aggressive as the low-cut filter on an SSL console EQ, as this high-pass filter is much more suited to very subtle sub-harmonic shaping for mastering than brute force filtering used for mixing. This filter is effective but also gentle and musical enough that it will almost intrude too much.

The next module is the Vintage Drive section, which provides a bypass button, a Drive control, and a Density control. Drive affects the overall amount of saturation while Density affects the amount of even versus odd order harmonics. An LED indicates the amount of saturation occurring, and this section reacts based on the signal level after the unit's input level trim. While mixing, I found the Vintage Drive controls effective and useful for shaping drum tones on individual tracks as well as on drum or drum/bass submixes. During mastering, acoustic songs benefited from the added density of the harmonic drive, while harmonically-rich rock and pop songs quickly changed character with even the slightest amount of harmonic drive. Fusion's drive section tastefully affects the midrange and upper midrange harmonics, as compared to SSL's VHD preamp circuit which seems to impart more high frequency harmonic coloration and feels more like a traditional overdrive.

Fusion's next processor is the Violet EQ; a two-band shelving EQ with selectable low frequencies of 30, 50, 70 and 90 Hz and high frequencies of 8, 12, 16 and 20 kHz. Overall this wide-band shelving filter behaves similar to a Baxandall style EQ, with low frequency boosts and cuts gently extending to above 1 kHz and high frequency boosts and cuts starting as low as around 1 kHz. When used with only one or two dB of cut or boost, this EQ can create a subtle musical tilt across the entire frequency range. While the EQs provide ± 9 dB of gain, I found that only one or two dB of adjustment got me what I needed during mastering. For individual instruments, a larger amount of boost or cut may prove useful, especially when exaggerating HF boosts into the HF Compressor – the next processor in the signal path.

I found the HF Compressor section to be the most inspiring processor in the Fusion. For acoustic masters, individual acoustic instruments and vocals, the HF compressor smooths out peaky high frequencies, sibilance, and edgy transients in a musical way that reminds me of the way analog tape saturation tames transients while slightly softening high frequencies. The user controls include a threshold adjustment with a range of ± 10 dB, and a crossover knob sweepable from 3 kHz up to 20 kHz. As mentioned previously, the Violet EQ's high frequency boost can be pushed into the high frequency compressor to achieve some bright and open tones that don't sound harsh or sibilant. I found this useful on acoustic guitar and especially on vocal tracks for hip-hop and EDM mixes where the vocal needs to be extremely bright but not harsh. I don't have any other processors (analog or digital) that provide transient smoothing as effectively as the Fusion does on vocal and guitar tracks.

The fourth processing section is the Stereo Image processor, which consists of a Space knob and a Width knob. Basically, Space effectively spreads the stereo image beyond the width of your speakers by boosting the low frequency stereo information – like a traditional shuffler. The Width knob simply adjusts the volume of the stereo (side) information in relation to the mono (mid) information of a stereo track. This mid/side (Width) adjustment creates a natural and realistic increase in ambience and depth of field while the shuffler (Space) control can provide a more hyped version of the stereo information that often feels like a slight chorus effect. Each type of stereo enhancement is useful in the right context and having both options provides a wide range of sonic possibilities.

The final processor in the signal path of the Fusion is simply an audio transformer that may be engaged or left off. In general audio transformers will slightly roll off bass frequencies while adding bits of harmonic saturation, high frequency compression, and a pinch of phase shift. Many well-regarded analog compressors and mic preamps derive a large portion of their character simply from the choice of audio transformers. The tonal characteristics of a given transformer also relates to the level of the audio signal running through it. SSL's chosen transformer would fall into the relatively uncolored family of transformers. A miniscule sub bass roll off and mid-bass push can be heard along with a slight change in high frequency harmonics. This effect is highly signal dependent, and while I found the transformer subtly enhanced acoustic music, for harmonically rich synth-based pop, urban, and EDM music, the transformer reshaped the high frequencies (particularly in the upper vocal range) in a way that felt a bit buzzy to my ears. I found the transformer to be most effective on individual mix elements and stems, but less effective on stereo mixes during mastering.

An important consideration while using the Fusion is the level dependence of several of the processors. During mastering I typically reduced the input trim and raised the output level. On individual tracks, however, I often pushed high levels into the Fusion while lowering the output trim after processing the signal.

Each of the Fusion's processor sections provides its own lighted bypass button, and the processing order (including the patchable insert) can be switched around to many different configurations. Further, the Fusion's insert may be operated as stereo L/R or it may be operated in a mid/side configuration. Lastly, the operation of the pushbuttons and master bypass may be modified, providing options including pre or post input trim bypass modes, LED brightness control and relay switch feedback settings. Also, an Easter egg of sorts has been put into this hardware box, wherein a game of "Simon" may be played using the front panel buttons. I'll leave it to the user to learn how to enter the gaming mode!