Boss CS-1

A heavy squeezer with a dip and swell

The CS-1's defining trait is how much compression it applies regardless of where the knobs sit. Even with Sustain at its lowest position the pedal is working hard, and raising it deepens the effect until the amplitude audibly dips and swells, the classic pumping of a high-ratio compressor working overtime¹. For players who want that obvious, squashed country or studio-glass sustain, that is the point; for players who want transparent leveling, it is the pedal's main limitation.

Ovnilab's review also notes what the heavy squeeze costs in tone:

• A slight loss of highs and lows, described as a constricted or congested sound¹
• An output level a bit lower than unity at low Sustain settings, which is annoying when switching the pedal on and off mid-song¹
• A noise penalty at higher Sustain settings, though the noise is "not bad at all" at low settings¹

The construction, by contrast, drew no complaints: "The construction quality is typical Boss," meaning the same compact die-cast housing and switch feel as the rest of the compact line¹.

Sustain, Level and the Normal/Bright switch

The control set is minimal compared with later Boss compressors: two knobs and a switch⁵¹.

The Level knob's limited headroom is worth knowing before buying one used. Ovnilab's reviewer found that at the more usable low Sustain settings, the level knob has to be set to maximum just to approach unity gain, leaving no boost in reserve¹.

The Bright side of the switch is the pedal's other voice. Boss describes the switchable Treble mode this way⁵¹:

Rod Brakes, BOSS articles⁵

That two-mode design proved durable: MusicRadar notes that the Mooer Blue Comp's two-mode layout follows the CS-1's example⁶. On the used and modified market, the normal side has also proven tweakable, with Ovnilab's reviewer improving the lows by changing the resistor and capacitor values connected to it¹.

A different circuit from the CS-2 and CS-3

The CS-1 is not simply an early version of the compressors Boss sells today. Boss states plainly that "the first BOSS compressor pedal has a distinctly different circuit than the later CS-2 and CS-3 models"⁷. The CS-1 is an optical design: a photocoupler reads the signal and controls the gain element, which Boss says "offers a slower attack with a unique character"².

The CS-2 of 1981 moved to a different approach entirely. Boss explains that "while the CS-1 used an optical detector circuit, the next-generation CS-2 introduced a VCA for faster response," with subtle distortion in the VCA circuitry adding natural richness and an Attack knob for adjusting the response⁷⁸. Aion FX adds that the CS-2 was based on the Dyna Comp circuit, though significantly overhauled by Boss engineers⁸.

The CS-3 continues the VCA line, and on That Pedal Show, Dan and Mick described the family relationship: "CS2 and CS3 are very closely related," with the CS-3's addition being a Tone control⁹. TONEHOME summarizes the split: the CS-1 is optical, while the CS-2 and CS-3 use VCAs (voltage controlled amplifiers) to create the same effect¹⁰.

Bypass and noise

The CS-1 predates the true-bypass era. Ovnilab's reviewer found that "the footswitch is not true bypass, but the bypass is pretty clean," so the pedal should not noticeably darken your tone when switched off¹. The same is true of the CS-3, whose bypassed tone the same reviewer called fairly clear¹¹.

On noise, the practical answer is to keep the Sustain low. The noise penalty only appears at higher settings, and since the pedal compresses heavily anyway, low settings are where most of its usable sounds live¹.

Where it came from and where it went

The CS-1 has since been reborn as a digital model. Boss describes the CS-1 model in the PX-1 Plugout FX as offering "a distinctly different circuit than the later CS-2 and CS-3 models"⁷. Guitar Pedal X's timeline of Boss's early pedals likewise lists the 1978 CS-1 Compression Sustainer among the originals gathered up for the PX-1 project⁴.

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