The Boss SX-700 uses its surprisingly narrow 18-bit (in and out) audio path to its fullest. The overall sound is clean and uncompromising. You get a nice 95 dB signal-to-noise ratio at Boss-standard 44.1 kHz. There's plenty of great acoustic simulation and modulation on offer – just no dynamics processors of any kind.
There's a total of nineteen effects algorithms in the SX-700. They vary the order of the effect modules as well as the overall effect configuration (e.g. some algorithms feature the Roland Sound Space at the expense of certain other effects).
The unit features all-analog stereo connectivity. Its 1996 hardware. No S/PDIF here, pal. Regardless, the signal throughput gets very little added noise. Whatever hiss you hear can be tamed with some nice high-frequency EQ shelving. You also get full MIDI-support for exchanging messages and patches between devices. But, perhaps a rarity for Boss, there's no headphones output. Still, there's a nice little level switch in the back for toggling between +4 dB and -20 dB output.
Jay Leno's Garage
The SX-700 includes eight reverb algorithms: three rooms, two halls, a garage, a plate, and a non-linear one. Most of these feature a decay time up to a whopping 32 seconds. Room 1 and 2 sound sound average at best. Room 3 is a more detailed and pleasant effect making it ideal for vocals or acoustic guitars. The two halls in the unit are in a league of their own compared to the GX-700 halls with more parameters to adjust and a cleaner sound overall.
The SX-700 plate reverb is a far cry from the ones found in Boss guitar preamps of the era, providing greatly improved fidelity and way more paramaters to adjust (such as offering four types of plates as well as plate brilliance and depth). I found the plate reverb suffers least from graininess at high decay settings – even on that dreaded 32 seconds one.
The garage reverb sounds best at the biggest room size setting and provides a fine multi-purpose acoustic treatment (yet one not that reminiscent of a garage – unless it's Jay Leno's). The most complicated reverb, the non-linear one takes some taming to make it useful. It might work for David Lynch soundtracks.
Most of the built-in reverb patches sound great right off the bat. To my ears, all Boss reverbs work best at higher density settings with ample low-frequency trimming. Mind you, the SX-700 reverbs were later recycled in the Boss VF-1.
You might wonder why the SX-700 gives you only an early reflection level control and not an overall reverb level one. Actually, it does, and its right there under the ”level” button. For guitar, its best to set the direct volume to zero and both the left and right channel volume ratios to 60-40 for all effects. The level section includes volume ratios for all modules, not just reverb.
Nation of Modulation
The rest of the processing power of the SX-700 is dedicated to a robust modulation section. It offers seven types of delays, a crisp chorus, a fine flanger, two different stereo phasers, and a rotary speaker simulator rich both in tone and parameters. There is also an emulation of a hip vintage chorus on offer: The Roland Dimension D. It features seven operating modes as well as a mono or stereo input option.
To my ears the SX-700 Dimension D (referred to as ”Space Chorus”) sounds a tad too subtle when compared to the real thing. Still, it adds a nice width to vocals and synthesizers. Personally, I prefer the 2+4 setting for most uses.
RSS and the Rest
While the two- or four-note harmonist (or ”intelligent pitch-shifter”) sounds average, it tracks your notes fairly well. The three-band EQ does feature shelving operation, which makes it far more useful than a purely parametric module. And thankfully, the EQ module is included in every one of the nineteen algorithms at hand.
The much brouhaha'd Roland Sound Space (RSS) is included in the SX-700 – a big deal back in 1996. RSS simply allows for some pretty convincing 3D sound panning. With it you get to pan up and down, too. It works best in the ”sweet spot” of your stereo speakers – not so well with mere headphones.
Faux Amp Sim
Plugging in my guitar and indulging in some creative parameter adjustment I managed to get a sound reminiscent of a solid state amplifier by combining the rotary simulator with some EQ. The rotary section includes an optional subtle overdrive and a mic simulation which facilitated the aforementioned patch. It should also work fine with a bass guitar - just make sure you tame the dynamics with an external compressor. Maybe even punch in a centered RSS effect. This way you get at least one pseudo-preamp patch from the SX. Tinny it may be, but it has its uses. Think the Vox Pathfinder transistor series.
SX and GX, Best Buddies
Running the SX-700 in tandem with the guitar-dedicated GX-700 I was pleasantly surprised how well they mesh together. I simply bypassed the GX's modulation and acoustics effects and plugged it mono into the SX to sample the union. This marriage works. Whatever EQ issues I had with the signal coming from the GX I could remedy with the extra EQ in the SX. Clean sounds especially benefitted from the SX's much beefier reverbs. The Dimension D emulation works wonders for overdriven GX-700 tones, too.
The SX-700 is a fine piece of equipment with one serious flaw: there's no dedicated dynamics processing. Even with an average built-in compressor the unit could've replaced many other multieffects in the studio. This makes the SX-700 a useful, but lacking blue box of high quality tricks.