Source Audio ZIO Analog Front End + Boost review

This formidable new boost offers up a choice of preamp flavors and is just the sort of super-practical tone sweetener you'd want to superglue to your pedalboard

Source Audio ZIO
(Image: © Future / Olly Curtis)

Guitar World Verdict

Source Audio’s ZIO has a plethora of classy options just waiting to be exploited, whether you choose to use it as an always-on tone conditioner or as an on/off booster. The absolute practicality of having one of these on your pedalboard cannot be overstated.


  • +

    Compact size.

  • +

    Massive 20dB boost.

  • +

    Four preamp options.

  • +

    Adjustable signal brightness.

  • +

    Dual outputs.


  • -

    Cheaper boosts are available, but few are this versatile.

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Designed by Source Audio to “make everything sound better”, the ZIO, the company’s first all-analogue pedal, is a preamp/boost pedal that’s capable of up to 20dB of boost via a choice of four different preamp circuits to colour the sound. 

On top of that, it acts as a buffer and has a Tone switch that offers three different levels of capacitance to simulate cable length, allowing you to make your tone brighter or darker. 

The pedal has two outputs, the second one being available as a line output or to keep a tuner permanently connected on your pedalboard without being in the main signal chain. The footswitch can be used as a normal bypass or it can be set to mute the main output – which is useful for some silent tuning.

Source Audio ZIO

(Image credit: Future / Olly Curtis)

The JFET is the most transparent of the preamp circuits and will retain your core tone but make it louder and more robust. Unity gain on the pedal is at about 10 o’clock, allowing plenty of leeway to dial in a targeted boost. It’s great if you want pure amp distortion without recourse to a drive pedal, and at max will fire up the cleanest guitar amp.

You may wish to use the Low-Cut option, though, because that can keep things really tight, basically rolling off any really low-end from the signal and especially useful on gainier sounds.

The Studio option (based on Pultec EQ settings used in studios) is a real tone‑sweetener that combines a mild lower-mid scoop to reduce muddiness with a higher boost for clarity and articulation.

Finally, the E-Plex setting mimics the old favourite Echoplex preamp and can add a whisper of dirt and a focused midrange with some top rolled off. 

The obvious use for the ZIO is at the front end of your signal chain – a job it does admirably – but it also works well as the last pedal before an amp or as a sweetener and an extra push for your drive pedals. Overall, it’s a tiny box with big functionality.


  • PRICE: $/£199
  • ORIGIN: China
  • TYPE: Preamp and boost pedal
  • FEATURES: True Bypass
  • CONTROLS: Output, Circuit switch (JFET, Low Cut, Studio, E-Plex), Tone switch (Bright/Medium/Dark), Bypass/Mute switch, Bypass footswitch
  • CONNECTIONS: Standard input, standard outputs
    (Main and Tuner/Line Out)
  • POWER: 9V-18V DC adaptor
    20 mA (not supplied)
  • DIMENSIONS: 66 (w) x 104 (d) x 55mm (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.