Source Audio C4 Synth review

The One Series delivers a heavily editable synth pedal with 128 user presets and a lot of musical potential

Source Audio C4 Synth
(Image: © Future / Philip Barker)

Guitar World Verdict

A compact and comprehensive source of synth sounds and textures.


  • +

    Cool synth sounds with excellent tracking.

  • +

    Deep editing via app.

  • +

    128 programmable presets.


  • -

    Not much, but as with any synth pedal, watch your technique.

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Source Audio's One Series pedals can be run in stereo and mono, and share a number of features. With 128 onboard preset slots, these digital stompboxes are hugely powerful, and when used with the Neuro graphical editing and librarian software – a mobile app for all iOS and Android devices (cabled connection) and a desktop version for Mac and Windows – you are offered comprehensive control of the effect.

Here we are going to look at the C4 Synth Pedal. Like the others in the series – such as the Source Audio EQ2 Programmable EQ – there's a Control Input jack for the Source Audio Dual Expression Pedal and a USB port. You'll want that editing software close at hand to allow you to adjust editing parameters, stereo routing options and advanced EQ control, and of course to manage your presets.

Source Audio C4

(Image credit: Source Audio)

The C4 pedal is basically a modular synth in a box with six of its 128 presets accessible from pedal switches and the rest via MIDI. 

You get front-panel control over the sound via an Input level knob, a Mix knob that sets a blend of your guitar sound and the synth voice, and two Control knobs that tweak parameters specific to each preset. 

On top of that, you have Alt knob functions for envelope sensitivity and output volume. The key to using this pedal is to set up your presets via the Neuro app – there are loads of parameters to edit, plus a wealth of presets to load. 

As with any guitar synth, we’d remind you to be careful with your technique to avoid glitches, but the tracking here is generally slick and excellent, and you can dial in all manner of recognisable out-and-out synth sounds or just blend in a touch of ear candy weirdness for your dry sound. Overall, it's a compact and comprehensive source of synth sounds and textures.


  • PRICE: $239 / £249
  • TYPE: Synthesizer pedal
  • FEATURES: Selectable analog buffered orrelay based true bypass, 128 presets
  • CONTROLS: Control input switch, Input/Sense, Mix/Vol, 1, Control 2, Preset switch, control, Bypass footswitch
  • CONNECTIONS: Standard inputs (1 & 2), standard outputs (1 & 2), USB, control input
  • POWER: 9V DC adaptor (supplied) 165 mA
  • DIMENSIONS: 70 (w) x 114 (d) x 51mm (h)
  • CONTACT: Source Audio

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Trevor Curwen

Trevor Curwen has played guitar for several decades – he's also mimed it on the UK's Top of the Pops. Much of his working life, though, has been spent behind the mixing desk, during which time he has built up a solid collection of the guitars, amps and pedals needed to cover just about any studio session. He writes pedal reviews for Guitarist and has contributed to Total Guitar, MusicRadar and Future Music among others.