Easy MXR-style Foot Control Knob Mod for Any Guitar/synth Effects/FX Pedal.

If you play amplified guitar or work with electronic instruments you'll be familiar with and may well own some effects pedals. While these are useful, interesting and fun they can be frustrating in certain respects, one of which is the need to grovel on the floor in order to make adjustments to them.

While this was less of an issue in the early days when designs were simpler, the number of variable parameters and switchable options on many recent and current models means more knobs to twiddle. Various strategies for dealing with this have evolved, but none are ideal. Some pedals can be connected to some kind of secondary remote control, but this obliges you to deal with two units instead of one. Parking pedals on a stand or desktop and controlling them manually is another option but rather defeats their purpose when playing a two-handed instrument.

There have been other attempted workarounds, including aftermarket knobs with protruding levers, but to my mind the only truly satisfactory idea is the rubber knob cover associated with classic MXR pedals, an example of which is shown below. Essentially a small rubber cylinder pushed over an existing control knob, it allows you to operate the knob by nudging it with the side of your foot. These can be retrofitted, but the assumption seems to be that they fit knobs of one particular size and benefit from an uncluttered control layout as typified by the MXR design.

As I liked the idea of being able to do this on a wide range of pedals with assorted knob sizes I devised a simple way of copying the MXR approach using ordinary rubber ferrules of the kind use on walking sticks/canes.

You really only need one tool, which is a pair of calipers (or a ruler and keen eye!) that will allow you to determine the size of ferrule that fits a particular knob. Having done your measuring you just need to acquire whatever size(s) of ferrule you'll need. Some shapes may work better than others, but this is easy to take into account given their intended purpose here. If you can't find an exact ferrule/knob size match, replacing the knob with one that can be matched is a possibility; keep the original in case you decide to undo the mod.

If at all possible choose real rubber ferrules rather than the plastic rubber substitute that's often used instead and is often wrongly described as 'rubber'. Real rubber ferrules are more flexible, making them easier to install and remove and also providing better grip in use. Ideally choose a design that includes molded vertical reinforcing flanges around the shaft socket, as with the examples shown. For our purposes their intended function is irrelevant, but they provide additional grip when the knobs are rotated, which is helpful.

There are plenty of eBay and Amazon listings for ferrules of all shapes and sizes, but they can often be obtained more cheaply from local hardware outlets (ideally the old-fashioned kind that just has them in boxes that you can rummage in!).

There are a few optional extra items which are dealt with below.

Take a ferrule of the appropriate size, invert it, then press it firmly onto your chosen knob. Repeat this procedure with other knobs as required. That's pretty much it.

There's one refinement you can add, which is some sort of pointer that shows you the knob's position (the design of the MXR originals, as shown here for reference, allows the knob's actual pointer to remain visible). Of course we should all be able to judge the adjustments we make by ear, but... On the examples shown here I made some very satisfactory pointers from short lengths of very thin wire with white insulation scavenged from a scrapped electronic device. These were fitted between the pips on the ferrule's surface (use pointy tweezers) and held in place with the tiniest smear (use a toothpick) of epoxy adhesive, the surfaces having been slightly roughened with very fine sandpaper beforehand to improve adhesion. This would have been less easy or impossible with many other ferrule designs, but in such cases a simple dot or line of white paint would do the same job perfectly well (perfectionists can mask off the paint's edges!).

A couple of instances of this mod proving its usefulness are shown in the introductory photo.

The Behringer Spectrum Enhancer is a clone of a classic short-lived Boss pedal that now commands huge sums on the used market (the Behringer version is less noisy than the original, by the way). It's essentially a selective EQ that can enhance a chosen frequency band; guitarists will set it at a point that sounds good and then mostly leave it as it is. When used with a synth, however, it's much more interesting to be able to sweep either control through its full range in real time while keeping both hands free for keyboard playing and/or making other adjustments. This mod makes this possible - and the pedal stays on the floor.

The Boss Super Octave is a more complicated beast with a cramped four-knob layout. When confronted with such a design it's clearly impossible to add ferrules to all the controls, so it's just a matter of choosing those that can most usefully be adjusted in real time. In this case both the direct level control and the multi-function parameter control have been converted for foot operation, the latter being switchable between range, drive and the level of the second of the two available octaves. The advantage of this particular tapered ferrule design is very apparent here, as it avoids binding on the two remaining knobs which can be adjusted by hand as usual.

A quick reassurance: if you test this project on a single pedal and find that it skitters away from you, don't worry; once you plug some cables into the pedal it'll stay put. If you use a pedal board the problem obviously won't arise at all.

And that's really all there is to this very easy Instructable!