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The Pinnacle of Classic Chorus, Flanging/Doubling, and Tube Tremolo Effects.

Taking you deep down the rabbit hole of classic analog modulation, UAFX Astra Modulation Machine serves up the most sonically authentic bucket-brigade chorus/vibrato, studio flanger/doubler, and tube-driven tremolo effects ever placed into a single stompbox.

Built upon our powerful new UAFX dual-engine processing and unmatched levels of quirky analog realism, Astra delivers richly addictive vintage modulation, beautifully crafted to inspire you for decades.

Texture your tones with iconic Japanese bucket-brigade chorus/vibrato, circa 1976

Explore the outer limits with legendary rackmount bucket‑brigade studio flanging/doubling

Get all the heavenly goodness of 1960's tube-driven tremolo, direct from your favorite American guitar amps

Quickly access sounds with Live/Preset modes, and play with silent switching, preamp coloration, and true/buffered bypass*

Download additional Phaser X90 and Dharma Trem 61 effects at product registration

Build your pedalboard around timeless UA design and robust craftsmanship, built to last decades


Chorus Brigade: Iconic Japanese Modulation

Chorus Brigade: Iconic Japanese Modulation

Upon its release in 1976, this legendary gray bucket-brigade stompbox changed the sound of music with its thick, luxuriant chorus and wavy vibrato. Astra's Brigade Chorus mode gives you the most complete circuit emulation of this landmark unit — including its preamp section for authentically thick, saturated sounds — letting you paint with subtle ripples of analog texture and tone, adding chewiness, shimmer, and motion to everything you play.

Flanger/Doubler: A Rackmount Studio Classic

Flanger/Doubler: A Rackmount Studio Classic

Packed with late-'70s bucket-brigade tech, this classic rackmount studio flanger/doubler is famous for stunning whoosh effects, organic thickening, and a parade of wild sounds that go way beyond typical flanger boxes. Astra's Flanger/Dblr effect is the only end‑to‑end circuit emulation of this ultra‑rare unit, capturing its original features to a "T" and putting impossibly dense, complex flanging/doubling right at your feet.

Trem 65: Authentic Tube Amp "Shake"

Trem 65: Authentic Tube Amp "Shake"

Few things compare to the optical tube-driven tremolo of '60s American amplifiers. Deep, undulating, and the very essence of vibe, Trem 65 is a faithful emulation of this classic circuit. From shimmering ripples to choppy mayhem, every dynamic detail is captured in UA style, down to the complex interactions between the light source photoresistor and 12AT7 driver tube. Plus, you can explore further and create your own trem textures with variable sine and square wave settings.

Dual Stereo Modulation Engines for Endless Creativity

Dual Stereo Modulation Engines for Endless Creativity

Astra's UAFX engine powers separate stereo instances of each modulation effect, thanks to its unique dual‑engine processing. It's like having two bucket-brigade hardware units running simultaneously — or even dual tremolo circuits — giving you a full stereo spread of complex, jaw‑dropping textures.

A State-of-the-Art Stompbox

A State-of-the-Art Stompbox

With modern, high‑powered features like studio‑grade conversion, dual‑processing engines, additional downloadable effects at registration, Live/Preset modes, true/buffered bypass,* and silent switching, Astra Modulation Machine has your colors — now go forth, and paint your masterpiece.

Watch the Reviews

      UAFX Control App & Owner's Manual

      Note that Astra Modulation Machine requires a modern 400 mA isolated power supply (sold separately). Go here for power supply recommendations.


      Flagship, no-compromise stompbox offering the most authentic bucket-brigade and tube-driven tremolo effects ever captured in an effects pedal

      End-to-end emulation of iconic Japanese chorus/vibrato pedal

      Complete circuit capture of legendary '70s rackmount studio flanger/doubler

      Stem-to-stern model of tube-driven optical tremolo from classic '60s American amps

      Store and recall your favorite preset, silent switching, and true/buffered bypass*

      Free Phaser X90 and Dharma Trem '61 effects, downloadable at registration

      Customer Reviews

      Astra Modulation Machine

      Overall Rating


      D. Stevens

      May 11, 2023

      Incredible Sounding Pedal

      The Astra is jam packed with features and sounds that inspire me every day I plug into it.
      I would love to have a full on Uni-Vibe option, that would take this pedal over the top.

      G. Saginario

      March 22, 2023

      fantastic vintage sound!

      fantastic vintage sound!

      D. Stevens

      February 18, 2023

      Incredible Sound

      Very lush and rich sounding pedal. It literally sounds expensive and that's exactly what you pay for. UA knocked this one out of the park.

      C. Cochran

      October 8, 2022

      Awesome sounds, needs more functionality.

      The stereo chorus is worth the price of the pedal, absolute magic. I wish there was a mode with depth and rate controls though. L The flanger is a PITA to use, I really really wish it was an Electric Mistress instead of the MXR. The trem and phase 90 are great as well.

      C. Jones

      June 15, 2022

      Least interesting of the initial 3 UAFX pedals

      I have the Golden Reverberator and Starlight as well. In comparison, this one leave a little to be desired. The chorus is great but simple. Would love an update with a rotary option and maybe a tape doubler like the Strymon Deco. There's so much potential for this to be an incredible pedal since they could in theory add more algorithms.

      M. Hakenson

      March 17, 2022

      Good pedal but it needs more effects for the price

      This is a good sounding pedal but it lacks enough effect variety for the money. You alrady own dytronics tri-chorus & the dimension D. Add them. A Uni-vibe or Leslie would be great. I owned it for a few days but returned it and bought something with more features & effects. Sorry. I’d buy it again because of the sound quality if it only had more choices.

      B. Vavra

      January 17, 2022

      Good but needs wow factor.

      Pedal sounds great and holds true to those vintage sounds. Dharma trem adds something new to the already laden landscape of modulation multieffects pedals.

      I think this pedal would be a game changer if it included a more versatile chorus option. The brigade one knob sounds fantastic, but adding something like a tri-stereochorus algorithm would make the pedal something I couldn't ever sell.

      P. Ghignone

      September 27, 2021

      Phenomenal Sounds - all it needs is presets or MIDI or preferably both

      The sounds in this pedal really are sublime, I honestly can't make one complaint about them. The chorus is incredible, the 65 trem is spot on, and the fact no one talks about the uni-vibe in the Dharma-Trem is insane to me, it's that good. I also like the fact that the sounds are expandable as well, keeps me excited for the future of this pedal.

      Really, the only thing lacking from this pedal is the lack of Presets (1 only) and MIDI functionality. Some people complain about the knobs having different functions for different effects, but this honestly would not be an issue if more presets were available, you could just dial in all your favourite tones and save them, and barely need to use the knobs again.

      The issue is that for a pedal at this price point, being limited to just 1 preset is simply not up to the standards set by its competitors. MIDI functionality would also be standard. It can be marketed as a studio tool first, but it's a pedal, not a rack unit, and it needs to be treated as such. I truly hope they add these features in the future, and they wouldn't be the first company to do it either.

      D. Morisset

      August 16, 2021

      I want more modes and presets.

      I spent the night playing the Astra with headphones, using the Walrus Audio ACS1 Amp and Cab Pedal.
      The Tones are superb.
      What I would like, is a Univibe and Rotary Modulations, in stereo. Since the Phaser X90 and Dharma Trem 61 are available online, I guess the template for more Modulation Downloads already exists.
      Secondly, I would love to be able to store more presets, at least 1 preset per Modulation, in addition to storing the last dialed in parameters for each Mode.
      EXH does this with the Oceans 12 and having these features would make the pedal more Pedalboard friendly.
      I don't record in any studio, but I do jam sessions and play guitar at church, so the less noodling with the board the better.

      That being said, this is the First Flanger Setting that I have tried that I like. Very, Very nice without the harsh swirling tones I associate with Flangers.

      The Chorus setting is simply sublime.

      E. Bass

      May 19, 2021

      Great on guitars - also on synths

      Really impressed with this so far, the thing sounds fantastic.

      D. Jackson

      May 6, 2021

      The Best Modulation

      I have owned a lot high end modulation pedals and this one tops them all.

      a. dhar

      May 5, 2021

      Mod to the Max

      Being in possession of some vintage classics, purchased Astra mainly to enable to have the mod sounds in one unit. Astra went beyond expectations. Upon first placement on my pedalboard, I have to say the depth and character of each sound is stellar. The build is superb but the effects are the real star here. The research that went into this must have been phenomenal. UA has captured the mojo of the best and this unit outshines my "standard" and now weary classic pedals. Thank you UA

      c. nishimura

      April 15, 2021

      Extremely tasteful

      The Good: Sounds here are extremely tasteful, stereo is outrageously lush. This pedal will knock plenty, if not all, of your modulations off your board effortlessly. Every setting is spectacular, usable and inspirational. A painful kind of love can be felt that went into this.

      The Sad: Nothing gets wild or remotely experimental, a missed opportunity to add innovative new parameters with the wealth of extra knobs at hand. Toggle switches can be awkward to access. Price, well what did you expect?

      M. Albergo

      March 23, 2021


      nuff said