Any modern producer will be aware of the significance of effects when mixing a track and, with the dominance of in-the-box techniques, it's easy to forget that there is much to be gained by exploring the floor-based world of metal bricks so beloved of guitarists.
Whether you are using the latest digital all-singing synth or drum machine with onboard effects, or a vintage mono synth, there is probably a guitar stompbox for you. Ironically, guitarists already had access to a range of commercially available electronic effects boxes before Bob Moog popularised synthesis with the Minimoog in 1970 and things changed forever.
Old vs new
It was the transistor that enabled these small boxes to be designed and built - with designers getting ever more adventurous with what they could do. Like the world of retro-synthesis, there is a lot of argument over the sound of 'original' effects pedals vs their newly-built brethren.
Although some guitarists will always argue the merits of a pure tone determined only by the right combination of guitar, amp and cab, others embrace live effects with aplomb, making them an essential part of their sound.
Despite the computerisation of so much of the music technology environment, there is a constant stream of new stompboxes hitting the streets. In some cases digital technology is used to harness the best available methods of emulation, but in others you find small-scale producers making new and inventive approaches to analogue processing.
There is also a strong market for recreations of classic pedals from original manufacturers and vaguely-named cut-price clones. Fitting into this niche are more expensive, hand-crafted pedals that attempt to copy every last detail of specific boxes from the '60s, '70s or '80s.
Dishing the dirt
Let's look at what the stompbox landscape offers in terms of processing. If you want to add instant dirt to any synth, then a distortion or overdrive pedal is the perfect place to start - and frankly it's a minefield.
In all cases, pedals of this type will turn a beautifully curved sine wave into something more angular - the heavier the effect, the closer to a square wave the sine will become. Of course, unless you happen to have a penchant for monophonic sine wave solos, the output is likely to be far more complex than a straight square wave.
The basic rule here is that, the simpler the sound and the fewer notes you play at the same time, the greater the degree of distortion you can apply before things turn overly cacophonous. Pedals with metal or screamer in the name tend to deliver heavy distortion flavours - sometimes with little ability to dial down the effect.
Others that allude to blues or crunch usually offer a tamer effect. In all cases, it can be helpful to have some form of filtering after the distortion. Some - mainly bass-oriented - pedals offer a mix control. So, when it comes to nasty acidic baselines or guitar-style synth leads, a dose of distortion goes a long way.
The second area where stompboxes prove most popular and useful is in the modulation department. This covers a lot of ground, and like flavours of distortion, is populated with numerous types of processor with many subtle variations.
The defining characteristic of traditional modulation effects is that they utilise some form of LFO (low frequency oscillator) to control a particular aspect of the sound. In the case of chorus and flanging, the design is essentially based around a short delay line where the delay time is modulated.
A phaser utilises a series of all pass filters (that change only the relative phase of the input), which creates a series of peaks and troughs in the frequency response when mixed with the original signal.
The distinctive phasing quality is created by the position of cancellation and reinforcement points being swept up and down by an LFO. There are many variations on the modulation theme that also takes in amplitude modulation (tremolo) and frequency modulation (vibrato) amongst others.
Delay, tone and control
Stompbox delays are also worthy of discussion, but the synthesist may ask - if I don't need to have an effect built into a small metal box with a switch, why not use a rack-mount delay? This gets right to the core of why stomp boxes are worth exploring - tone, simplicity and usability.
Chorus and flanging are based around a modulated delay. Many of the most favoured examples use bucket brigade delay line (BBDs). Like a digital delay, the signal level is sampled at regular intervals and passed into a buffer, but here analogue techniques rule the roost.
The 'buckets' are a line of capacitors which pass charge from one to the next and, unlike digital, the quality degrades slightly at every step, making the output far less perfect and clean - great! These were at the core of most of the chorus units built into the synths of the '80s (eg Roland Juno). They helped fill out the sound of single-oscillator designs and are one of the main reasons for investing in a pedal like the Electro-Harmonix Memory Man Deluxe.
More recently, manufacturers have explored digital emulation as a way of accessing a wider range of tonal variations within a single box. Line 6 was one of the first to do this well and still produce a series of pedals and rack units that do just this. Its Pod range offers a great way to access a bunch of effects combined with amp simulation.
A more specific premium option is the Strymon El Capistan, which goes to great lengths to try and capture the sound of tape-based delay. The beauty of digital in this instance is that the amount of degradation and noise can be chosen by the user. Strymon also makes dedicated stomp box reverbs like the blueSky and the highly-regarded BigSky.
So back to the earlier question - why stompbox, not rack or plugin? Apart from individuality of sound, interactivity plays a huge part. Having a limited number of controls helps, but there's also a lot of creative fun to be had by tweaking in real time. Playing a synth line with one hand while controlling delay time and feedback is fun and sounds great, plus allows you to create sonic moments that are less easily achieved in the DAW environment.
Besides the hands-on aspect, some pedals include further control elements that up the ante in terms of audio mangling. The EHX Memory Boy Deluxe has an expression pedal input to which can be patched CV signals from external LFOs, envelopes or synths. This in turn can control the rate and depth of LFO modulation, delay time or feedback.
The Pigtronix Envelope Phaser is plastered with knobs, switches and sockets, and combines a traditional LFO-controlled phaser with an envelope section triggered by the incoming signal level.
Some effects, like the auto-wah, use the input level as the primary source of modulation. Companies like Koma Elektronik blur the line between synth module and stompbox entirely with its FT201 Analog Filter/Sequencer and BD101 Analog Gate/Delay. Pittsburgh Modular take this even further with the newly-announced Patch Box - a modular beneath your feet!