This article contains complete operating instructions for the UAFX Astra Modulation Machine effects pedal. 

• Astra Quick Start
• Astra Overview
• Astra Power
• Astra Connections
• Astra Operation
• Astra Controls
• Astra Effect Details
• Astra Settings in the UAFX Control App
• Astra Specifications
• Astra Safety

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A Letter From Bill Putnam, Jr.

Congratulations on your new UAFX pedal. We know that buying any new piece of gear requires an investment of time and money, and we aim to make your investment pay off!

At UA, we are dedicated to the idea of building “instant classics” — the type of music and audio gear that delivers album-worthy sounds to inspire you for decades.

UAFX pedals represent more than 20 years of research into vintage analog effects, coupled with next-generation digital engineering and rock-solid reliability.

Please let us know how we’re doing. Feel free to reach out to us via our website www.uaudio.com, and via our social media channels.

Thank you for your support, and enjoy your sonic exploration!

Sincerely,

Bill Putnam Jr.

 

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Astra Quick Start

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Astra Overview

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.

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. 

Silent Switching

UAFX pedals are designed to switch on and off seamlessly and silently, using relays and advanced circuitry.  When in true bypass, you may hear the mechanical relay switching from the hardware, but you do not hear the switching in the audio signal. There are no mechanical noises from the pedal with buffered bypass because the physical relay is not used. 

Free Bonus Effects

To get the free Phaser X90 and Dharma Trem 61 modulation effects, register your pedal with UA Connect or the UAFX Control app. To get UA Connect and UAFX Control, visit:

 

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Astra Power

To learn how to power your UAFX pedal, go here.

 

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Astra Connections

To learn how to wire your UAFX pedals, go here.

 

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Astra Operation

Live Mode and Preset Mode

In Live mode, the sound reflects the current positions of the knobs, switches, and LEDs on the pedal, and the left footswitch toggles the Live mode effect on/off.

In Preset mode, you hear the settings that are stored as a preset, and the current positions of the knobs and switches do not reflect the sound. Instead, all knob and switch positions are internally set to their stored positions, and the right footswitch toggles the preset effect on/off.

Live Mode

To enter Live mode, press the left footswitch. Press the left footswitch again to toggle the live effect on/off. The left footswitch LED is lit red when the Live mode effect is on.

Preset Mode

To enter Preset mode, press the right footswitch. Press the right footswitch again to toggle the preset on/off. The right footswitch LED is lit green when the preset is on.

Note: The right footswitch (see below) can be set to other behaviors in the UAFX Control app.

 

Right Footswitch

The behaviors of the right footswitch can be changed to suit your preferences with the UAFX Control app. Note that the left footswitch always toggles Live mode, where the knobs and switches are “what you see is what you hear” (except the speed knob, if tempo is tapped).

Astra’s right footswitch has two available settings:

Preset*	Live mode and Preset mode are available. Tap tempo is unavailable.
Preset + Tap	Live mode, Preset mode, and Tap Tempo for both modes are available.
*Default setting from factory and after restoring defaults

Preset

When set to Preset, the right footswitch immediately loads the preset with its stored tempo, and toggles the preset on/off. Tap tempo is unavailable with this setting.

Preset + Tap

When set to Preset + Tap, the right footswitch performs multiple functions.

Load Preset: Hold the right footswitch for 1.5 seconds (or longer) to load the preset with its stored tempo when the footswitch is released. The Effect Type LED blinks rapidly when the preset is armed for loading. 

Bypass Preset: Hold the right footswitch for 1.5 seconds (or longer) to bypass the preset when the footswitch is released. The Effect Type LED blinks rapidly when the preset is armed for bypass. Tip: Tap the left footswitch twice to quickly bypass the pedal from Preset mode.

Tap Live/Preset Tempos: Short-press (don’t hold) the right footswitch twice or more to tap quarter note tempo. In Live mode, the right footswitch LED blinks red at the current tempo. In Preset mode, the right footswitch LED blinks green at the current tempo.

 

Stored Preset

You can store a preset on your UAFX pedal, and recall it using the right footswitch. A default factory preset is included.

When you store a preset while in Live mode, the position of all knobs and switches on the pedal are saved. So when you make a great sound in Live mode, storing it is as easy as holding down the store switch. 

When you store a preset while in Preset mode, only those knobs and switches that have changed since you loaded the preset are saved. So, when saving in Preset mode, what you hear is what is saved, and not the current positions of the knobs and switches. 

To store your sound as a preset

1. Set your sound as you want it stored in the preset. 

2. Press and hold the STORE switch in the down position until the green PRESET footswitch LED blinks rapidly (about 0.5 seconds).

Preset Notes

• The speed in Preset mode and Live mode are completely independent.

• When you move a knob or switch in Preset mode, the settings for the sound immediately jump to the new knob or switch position. 

• When you switch the effect type in Preset mode, all settings change to their defaults, which are optimized for that effect. Use the defaults as a starting point when you are looking for a great chorus, flanger, or tremolo sound.

 

Effect Bypass Routing

Astra Modulation Machine effect bypass routing can be set for true bypass or buffered bypass using the UAFX Control app. Bypass routing determines how the pedal behaves when the effect is off.

 

True Bypass

When bypass routing is set for true bypass and the effect is off, the dry signal is pure analog dry-through from input to output, without buffering or any other circuitry, via mechanical relays. By default, your UAFX pedal is set for true bypass. 

When set for true bypass and the effect is on, the output is buffered.

Buffered Bypass

Buffered bypass can be set in the UAFX Control app. When bypass routing is set for buffered bypass, the output is buffered when the effect is on, and also when the effect is off. 

When the effect is off, the dry signal remains analog dry-through.

 

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Astra Controls

Astra Modulation Machine’s knobs and switches control each modulation effect similarly, but the functions of the controls vary, depending on the currently selected effect. See the individual modulation effect details section for complete control descriptions.

Speed

Adjusts the modulation rate.

Depth

Adjusts the modulation amount.

Intensity

Adjusts aspects of the modulation character, depending on the effect.

Shade

Adjusts aspects of the modulation character, depending on the effect.

Shape

Adjusts aspects of the modulation character, depending on the effect.

Effect Type

Push this switch up or down to change the modulation model. When you push the switch repeatedly, the pedal cycles through all available effects. 

Tip: Register your pedal to get the bonus Phaser X90 and Dharma Trem 61 effects.

Effect Type LED

The currently selected effect is indicated by this LED. A red LED indicates that the effect printed on the pedal is selected. The bonus Phaser X90 effect is selected when the top LED is green, and the bonus Dharma Trem 61 effect is selected when the middle LED is green (the bonus effects don’t have labels).

Store

The STORE switch saves the current sound as a preset. Press and hold the STORE switch in the down position until the green PRESET footswitch LED blinks rapidly (about 0.5 seconds).

See the Stored Preset section for additional details.

Variation A/B

Each modulation model (Chorus Brigade, Flager Dblr, Trem 65, Phaser X90, Dharma Trem 61) includes two variations that are selectable with the A/B switch. These modes are unique variations within each modulation type. 

Use the A/B switch to select variations within the selected modulation type. The variations for each effect are shown in the effect details section. 

Left Footswitch LED

The left footswitch LED is lit red when the live knob and switch settings are active. 

Left Footswitch

Press to toggle the effect on/off with current knob and switch settings.

Right Footswitch LED

By default, the right footswitch LED  is lit green when the preset is on. Other behaviors are possible, depending on the right footswitch setting. 

Right PRESET Footswitch

The right footswitch can be set to access the preset, or provide tap tempo and access to the preset. See Right Footswitch for more information 

 

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Astra Effect Details

Each UAFX effect has a unique sound and control set. The specific function of the knobs and switches within each effect varies, depending on which functions are needed for optimal control of the specific effect. 

This section contains the specific control details for each effect, along with a controls map diagram for quick reference. You can download the control map diagrams, along with a blank recall sheet for noting your own settings, via the link below.

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.

Note: With Chorus Brigade, some knobs do not function. To reproduce the original sonics as accurately as possible, the control set from the original hardware is provided. When you turn a knob that is inactive, the Effect Type LED blinks rapidly, indicating that the knob has no function. 

Control Details (Chorus)

Control	Description	Additional Info
Speed	No function (N/A)	When turning, the Effect Type LED blinks to indicate knob is inactive
Depth	No function (N/A)	When turning, the Effect Type LED blinks to indicate knob is inactive
Intensity	Chorus intensity	Combines speed and depth on a single control
Shade	Output level	Noon is unity gain
Shape	No function (N/A)	When turning, the Effect Type LED blinks to indicate knob is inactive
Mode	When used in stereo, sets mode to classic or dual stereo	In classic mode, dry signal appears at left output, and wet signal appears at the right output.  In dual stereo mode, the pedal processes each side separately, with the left and right chorus LFOs 90º out of phase for maximum effect.

 

Control Details (Vibrato)

Control	Description	Additional Info
Speed	Vibrato rate
Depth	Vibrato depth
Intensity	No function (N/A)	When turning, the Effect Type LED blinks to indicate knob is inactive.
Shade	Output level	Noon is unity gain.
Shape	No function (N/A)	When turning, the Effect Type LED blinks to indicate knob is inactive.
Mode	When used in stereo, sets the mode to classic or dual stereo.	In classic mode, dry signal appears at left output, and wet signal appears at the right output.  In dual stereo mode, the pedal processes each side separately, with the left and right vibrato LFOs 90º out of phase for maximum effect.

 

Flanger Dblr

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.

Note: With Flanger Dblr, when the Right Footswitch is set to Preset + Tap, the tempo is set to 1/8th notes, and controls the flanger/doubler rate. 

Control Details

Control	Description	Additional Info
Speed	Rate	The rate of modulation applied to the delay time LFO.
Depth	Width	The amount of modulation applied to the delay time LFO.
Intensity	Regeneration (feedback) amount	The amount of effect routed back to its input; as the value increases, a more resonant signal is produced.
Shade	Wet/dry mix	Noon is max flange (50% wet).
Shape	Manual sweep	The delay time; adjusts the overall sound, imparting different vowel-like qualities in the sweep.
Mode	Normal or inverted	Inverts the phase for a more hollow sound.
Variation A	Flanger mode	Use for a classic flanging sound.
Variation B	Doubler mode	At short settings, this creates more of a doubling effect, at longer settings creates more of a chorus-like sound.

 

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.

Control Details

Control	Description	Additional Info
Speed	Rate	Slower speeds have more depth, mimicking the behavior of the optical tube circuit.
Depth	Intensity	Like original tube circuit, at higher speeds the Intensity has less effect
Intensity	LFO Shape	Adds subtle edges to the waveform
Shade	Input drive	Noon is unity gain. Increase this control to compensate for the perceived volumes drops in volume that can occur with tremolo.
Shape	No function (N/A)	When turning, the Effect Type LED blinks to indicate the knob is inactive.
Mode	Dual mono or stereo panned	When stereo panned, tremolo pans 180º left and right on each swing.
Variation A	Sine wave	Sounds like the original tube circuit.
Variation B	Square wave	The sine wave is squared off for a more aggressive sound.

 

Phaser X90

Classic Phasing Effects

Based on the classic “script” and “block” phaser effects — available as a free bonus with pedal registration. 

Register to get this effect

This additional effect is available after you register your Astra Modulation Machine. To select the Phaser X90 effect, push the Effect Type switch to cycle through the modulation effects. Phaser X90 is selected when the top Effect Type LED is lit green (the bonus effects don’t have labels).

Control Details

Control	Description	Additional Info
Speed	Rate	Speed range is different between Script and Block circuits.
Depth	No function (N/A)	When turning, the Effect Type LED blinks to indicate the knob is inactive.
Intensity	No function (N/A)	When turning, the Effect Type LED blinks to indicate the knob is inactive.
Shade	Input drive	Noon is the stock setting, turn up for more harmonics.
Shape	No function (N/A)	When turning, the Effect Type LED blinks to indicate the knob is inactive.
Mode	LFO Mono/Stereo Phase	In Stereo Phase, the two sides are 180º out of phase, for a swirling, three-dimensional sound,
Variation A	Script circuit	Smooth and slow phase, for classic hard rock tones.
Variation B	Block circuit	Faster, more “chewy” phase, with higher max speed and feedback in the phase circuit.

 

Dharma Trem 61

Unique Dynamically Controlled Harmonic Tremolo

Harmonic tremolo is a unique combination of tremolo and phasing, where the signal is split into bass and treble components that are then panned between the filters with an LFO. These split signals are then summed back into a single signal, with the result being a tremolo that has both volume and phase-like components. 

With Dharma Trem 61, you can control the crossover frequency of the bass and treble components, and add dynamic control of the tremolo speed. The end result is a “dynamic harmonic tremolo,” a unique effect unlike anything else available. Dharma Trem 61 is available as a free bonus with pedal registration.

Register to get this effect

This additional effect is available after you register your Astra Modulation Machine. To select the Dharma Trem 61 effect, push the Effect Type switch to cycle through the modulation effects. Dharma Trem 61 is selected when the middle Effect Type LED is lit green (the bonus effects don’t have labels).

Control Details

Control	Description	Additional Info
Speed	Rate	Baseline speed, which can be modified by dynamic controls.
Depth	Depth	Interactive with Intensity; depth is consistent at any speed.
Intensity	Crossover from tremolo to pitch phase	Set at 10 o’clock for univibe-like sound, and set this fully on or off for authentic harmonic tremolo only with no pitch warble.
Shade	Dynamic speed threshold	Sets the threshold at which the dynamic speed is triggered. Start at noon and adjust to taste.
Shape	Dynamic speed amount   Turn Shape all the way down to disable dynamic control for classic early ‘60’s harmonic tremolo.	Sets the dynamic speed; when the Dynamic speed threshold is exceeded, the rate ramps up or down to this speed, then ramps back to the speed set on the Speed knob or via tap tempo.
Mode	Dual mono/LFO stereo phase	When set to LFO stereo phase, tremolo swings 180° left and right.
Variation A	Classic	Traditional harmonic tremolo
Variation B	Vibey	Phaser-like harmonic tremolo

 

Astra Default Preset

The default preset for Astra Modulation Machine provides a classic amp tremolo sound. You can replace this preset by storing your own.

Note that when you switch effect types in Preset mode, all settings change to their defaults, which are optimized for that effect. Use the defaults as a starting point when you are looking for a great chorus, flanger, or tremolo sound.

 

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Astra Specifications

All specifications are subject to change without notice.

Power requirements (power supply sold separately)	Isolated 9VDC, center-negative, 400mA minimum
Inputs	2 x ¼” unbalanced TS (input 2 for stereo connections)
Outputs	2 x ¼” unbalanced TS (output 2 for stereo connections)
Bypass modes (switchable within UAFX Control app)	True bypass via mechanical relays or buffered bypass
Input impedance	500 Kilohms (Mono In) 1 Megohms (Stereo In)
Output impedance	500 Ohms
Maximum input level	12.2 dBu
Maximum output level	12.1 dBu
Frequency response	20 Hz to 20 kHz, ±1 dB
USB Type-C	For registration and firmware updates via computer
Wireless technology Transmitted Frequency Range Maximum Output Power	Bluetooth v5 2.400 GHz – 2.4835 GHz +4.35 dBm
Dimensions (with knobs and protrusions)	Height: 2.56 inches, 6.5 cm Width: 3.62 inches, 9.2 cm Depth: 5.55 inches, 14.1 cm
Weight (unboxed)	1.24 lbs 0.567 kg

 

 

 

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Astra Safety

Caution: To help maintain the safety of your product, the chosen power supply must be a certified power supply complying with Limited Power Source (LPS) requirements with the following characteristics and electrical ratings: Isolated 9VDC, center-negative, 400 mA minimum, 2.1x5.5 mm barrel connector. Additional details at help.uaudio.com.

Before using this unit, be sure to carefully read the applicable items of these operating instructions and the safety suggestions. Afterwards, keep them handy for future reference. Take special care to follow the warnings indicated on the unit, as well as in the operating instructions.

• Read the instructions.

• Keep these instructions.

• Heed all warnings.

• Follow all instructions.

• Do not use this apparatus near water.

• Clean only with dry cloth.

• Do not block any ventilation openings. Install in accordance with the manufacturer’s instructions.

• Do not install near any heat source such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.

• Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other.

• Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles, and the point where they exit from the apparatus.

• Only use with attachments/accessories specified by the manufacturer.

• Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been dropped.

• Astra Modulation Machine does not contain a fuse or any other user-replaceable parts.

• A compliance marking label is provided on bottom of the unit. 

United States Class B Manual Statement

NOTE: This equipment has been tested and found to comply with the limits for a Class B digital device pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try and correct the interference by one or more of the following measures:

• Reorient or relocate the receiving antenna. 

• Increase the separation between the equipment and the receiver.

• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

• Consult the dealer or an experienced radio/TV technician for help. 

Japanese Class B Manual Statement

この装置は、クラスＢ機器です。この装置は、住宅環境で使用することを目的としています  が、この装置がラジオやテレビジョン受信機に近接して使用されると、受信障害を引き起こ. すことがあります。取扱説明書に従って正しい取り扱いをして下さい。VCCI-B

This is Class B equipment. Although this equipment is intended for use in residential environments, it could cause poor reception if used near a radio television receiver. Please follow instructions in the instruction manual.

Korea KCC: 해당 무선설비는 전파혼신 가능성이 있으므로 인명안전과 관련된 서비스는 할 수 없습니다.

License exempt. This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and (2) this device must accept any interference, including interference that may cause undesired operation of the device.

Le présent appareil est conforme aux CNR d'Industrie Canada applicables aux appareils radio exempts de licence. L'exploitation est autorisée aux deux conditions suivantes : (1) l'appareil ne doit pas produire de brouillage, et (2) l'utilisateur de l'appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible d'en compromettre le  fonctionnement.

Used electrical and electronic equipment should not be mixed with general household waste. Please dispose in accordance with local regulations.

• IEC 62368-1

• FCC ID: 2AXKQ2029

• IC ID: 26610-2029

Hereby, Universal Audio, Inc. declares that the radio equipment type Bluetooth LE Device (Residential) is in compliance with Directive 2014/53/EU. The full text of the EU declaration of conformity is available at the following internet address: Signed EU Declaration of Conformity.pdf