Universal Audio Astra Modulation Machine

Universal Audio Astra Modulation Machine

Regular price $549.00
1 in stock

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

Astra Modulation Pedal includes Phaser X90 and Dharma Trem 61 (w/ Registration)

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
  • Quickly access sounds with Live/Preset modes, and play with silent switching, preamp coloration, and true/buffered bypass*
  • Explore the outer limits with legendary rackmount bucket‑brigade studio flanging/doubling
  • Download additional Phaser X90 and Dharma Trem 61 effects at product registration
  • Get all the heavenly goodness of 1960's tube-driven tremolo, direct from your favorite American guitar amps
  • Build your pedalboard around timeless UA design and robust craftsmanship, built to last decades
  • *True/trails bypass selection available via UAFX Control software (coming Spring 2021).

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

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"

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

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

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.

UAFX Power Requirements

Note: Power supply is not included.

UAFX pedals require an isolated 9 volt DC, center negative, 2.1 x 5.5 mm barrel connector (same as standard Boss connectors) power supply, which can provide 400 mA of current. Each UAFX pedal must be connected to a separate power supply, or connected to an isolated power connection from a multi-output power supply. Daisy-chaining (running multiple pedals from one output of a power supply) is not supported. 

UAFX Power Recommendations

Any modern high-current pedal board power supply that meets the requirements below will work with UAFX pedals. Manufacturers such as Voodoo LabCioksTruetone, and Strymon make power supplies that work great with UAFX pedals.

Contact your authorized UA dealer for additional details and recommendations.


Each UAFX pedal requires 400 mA (milliamps) of current. If the supply cannot provide 400 mA of current, your pedal might not operate properly, even if the LEDs and switches seem to be working. It’s OK to connect a supply that can deliver more than 400 mA; the pedal only draws the current it needs, and will not be damaged as long as the supply is 9VDC.


An isolated supply provides power and grounding that is electrically separated, usually by means of a transformer for each connector. If the power connection isn’t isolated, you might hear noise and/or ground loop hum in the pedal signals. 

Multi-outlet supplies

If your power supply has multiple outputs, make sure that each output provides true isolation. Some low-cost supplies have separate connectors but don’t provide true ground and power isolation (the connectors might be internally daisy-chained instead of electrically isolated).


Be careful to connect your UAFX pedal to 9 volt DC power only. Higher voltages and/or AC power can damage UAFX pedals.


Connect your UAFX pedal to center-negative DC power only. For example, some effects (such as Eventide H9) require center-positive power. Center-positive supplies and/or cables typically (but don’t always) have a red connector tip.

Power Interruption

If power to your UAFX pedal is interrupted during operation, processed audio stops. However, your dry audio signal still passes through the pedal. When the pedal is unpowered, and when it’s starting up, the signals are pure analog dry-through from input to output, without buffering or any other circuitry, via mechanical relays. 

Daisy Chained Power

Daisy-chaining (running multiple pedals from one output of a power supply) is an unsupported configuration. UAFX pedals require isolated power for optimum performance.

What is an isolated power supply and why are you recommending it?

An isolated power supply has a power input that is electrically independent from its power output, and with multi-output supplies, the outputs are also electrically independent from each other. We recommend using isolated power to prevent ground loops and other noise issues. You can use a dedicated power supply for each pedal on your pedal board, but this is often both space-consuming and inconvenient. 

The best solution is to use a dedicated multi-output pedal power supply, but this is where isolation matters. Some cheaper multi-output power supplies have one power input that is simply cascaded to multiple outputs without any isolation, which is a common cause of noise issues. When buying a multiple output power supply, one should make sure that each output is individually isolated.

Incompatible Power Supply

The power supply listed below is known to be incompatible with UAFX pedals.

  • GigRig TimeLord

    Current Draw:

400 mA