Universal Audio Astra Modulation Machine review

A feature-stacked modulation stompbox that's out of this world

Universal Audio pedals
(Image: © Universal Audio)

Guitar World Verdict

Look no further for authentic recreations of vintage modulation effects.


  • +

    Superb, studio-quality sounds.

  • +

    Wide range of modulation.

  • +

    Highly tweakable.


  • -


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Having made its name in studio equipment, with authentic plug-in emulations that are powered by DSP and housed in hardware, Universal Audio's is staking a claim for our pedalboards with a trio of high-end stompboxes.

The range comprises the Golden Reverberator reverb pedal, the Starlight Echo Station delay pedal, and the Astra Modulation Machine that we have here. Each arrives with various mono and stereo options and a choice of three effects with toggle-switched variations.

In the case of the Astra modulation pedal, you can download an extra two effects via USB and store a single preset to the unit. It's simple: flick the Store switch and you’re done. There are two footswitches to access two different sounds. On the left, your footswitch accesses the Live sound – in other words, the sound as dialed in on the current positions of the knobs and switches. On the right, meanwhile, you've got your preset.

With emphasis on classic amp tremolos and iconic pedals, the Astra offers two variations on each effect plus two positions of the Mode knob, which offer different stereo options. 

There’s an accurate reproduction of a Boss CE-1 sound in both its Chorus and Vibrato modes, while the MXR Phase 90 is recreated in two incarnations with the subtleties of the early ‘script’ logo sitting next to the chewier ‘block’ version. 

An emulation of the vintage MXR Flanger/Doubler offers a familiar sound and serves up some decent ADT, too.  

Trem is represented not just by a typical Fender photocell sound with sine or square wave but also by its harmonic trem, with two variations – one more phasey than the other – and cool dynamic control of trem speed set up via the Shade and Shape knobs. A bit of tweaking also gets you into Uni-Vibe territory. 


  • PRICE: $399 / £355
  • TYPE: Modulation pedal 
  • FEATURES: Selectable True/Buffered bypass, Tap Tempo option 
  • EFFECTS: Chorus Brigade, Flanger Dblr, Trem 65, Phaser X90, Dharma Trem 61 
  • CONTROLS: Speed, depth, Intensity, Shade, Shape, Mode, Effect Type switch, Store switch, Mode switch (A/B), Pair switch, Preset footswitch, Bypass footswitch 
  • CONNECTIONS: Standard inputs  (1/Mono, 2/Stereo), standard outputs  (1/Mono, 2/Stereo), USB 
  • POWER: 9V DC adaptor (not supplied) 400 mA  
  • DIMENSIONS: 90 (w) x 144 (d) x 63mm (h
  • CONTACT: Universal 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.