MAS Effects Expression Slider

The MAS Effects Expression Slider is a desktop expression pedal from MAS Effects: instead of rocking a treadle, you move a fader with your hand, from your desk, a mic stand, or anywhere else the maker suggests. The Expression Slider plugs into any other pedal with an expression jack and gives you remote control of that pedal's expression function¹²³. It is sold in two forms: an expression-only version at $39, and a Volume control / Expression combo at $59¹.

What it does

In its basic form, the slider is an expression controller. You connect it to a pedal's expression input with a stereo (TRS) cable in the top jack, and moving the fader sweeps whatever parameter that pedal assigns to expression, such as delay time, reverb size or filter frequency⁴. The maker describes the idea simply: "Plug this into any other pedal with an expression jack to get remote control of that pedal."³

The combo version adds a volume function. MAS Effects states that "The combo version of this can be used as either an expression or a volume pedal (not simultaneously)"¹. In volume mode, the maker suggests two uses: put the slider in a series effect loop to get fully-cranked tube amp sounds at polite volumes, or put it in the pedal chain to knock off a few dB, which the maker compares to "the popular little black Amp Box"².

Versions and compatibility

The maker's page lists named editions of the slider, including Abduction and Split Skull, in both expression-only and Volume + Expression forms⁴.

A few practical points matter before you buy into the idea:

• The expression output uses a stereo (TRS) cable in the top jack. MAS Effects notes it "will not work well with Eventide, Line 6, or others that use mono TS cables"⁴.
• The potentiometer is a 100k or 10k linear type, depending on the option chosen¹.
• The units are often made-to-order and can be customized for additional fees⁵.
• Previous special editions exist, including a Desktop Expression Pedal Prototype / Special Edition Slider³.

The prototype and special edition units carry a B100k potentiometer, which the maker says "works well with EQD, Strymon, EHX, Matthews Effects, and more," while warning "It will not work well with Boss, Eventide, or Line 6." Their outputs are TRS and require a stereo cable⁶.

Where it sits on a board

Because it is a hand-operated fader rather than a floor pedal, the Expression Slider suits players who adjust expression from a desktop setup, a recording desk, or a mic stand position rather than mid-song with a foot⁴. As a volume control, the combo version works either in a series effects loop, where it tames a cranked amp's output, or in the pedal chain, where it trims level the way the maker says the little black Amp Box does². For players comparing options, the expression-only version sits alongside other expression pedals, while the combo version overlaps with volume pedals.