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UAFX Flow Vintage Tremolo Manual

This article contains complete operating instructions for the UAFX Flow Vintage Tremolo pedal from Universal Audio.


In this article



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, and via our social media channels.

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


Bill Putnam Jr.



UAFX Flow Quick Start


Download Flow Quick Start Sheet



UAFX Flow Overview

Three flavors of authentic tube tremolo, at your feet.

Evolved from our flagship Astra Modulation Machine, Flow Vintage Tremolo gives you three flavors of tube-driven wiggle and shake — from old school to modern — in a dapper, compact package.

Flow is a mono in/mono out tremolo pedal featuring three switchable tremolo modes, with a simple set of controls for speed, depth, and volume. In addition, Flow includes options for true or buffered bypass and tap tempo.

  • Get three stunning emulations of legendary tube amp tremolo effects, from opto to harmonic 
  • Explore rich, authentic tones and effects with perfectly emulated tube preamp section
  • Sync your trem with tap tempo and add boost effects with Volume control
  • Rely on timeless UA craftsmanship, built for years of rock-solid performance



UAFX Flow Power

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



UAFX Flow Connections

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




Get the Latest Firmware

Be sure to update your pedal’s firmware with UA Connect to get the latest features and functionality. To learn how to use UA Connect with your UAFX pedals, go here.



UAFX Flow Controls

The following controls are available on Flow.


Adjusts the speed of the tremolo effect. Slower settings (counter-clockwise) can introduce a lot of space and texture to your sound, while faster settings (clockwise) can provide more rhythmic stuttering effects.


Adjusts the amount of tremolo applied to the signal. At lower settings (counter-clockwise) tremolo is subtle, and at higher settings (clockwise) tremolo is very pronounced. 

Tremolo Type

Use this switch to select the tremolo model. 


Tremolo Type Details
Dharma Unique UA original harmonic tremolo effect. Harmonic tremolo combines 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 summed back into a single signal, with the result being a tremolo that has both volume and phase-like components. 
65 Optical tube-driven tremolo from a classic '60s American amplifier. Shimmering, rounded ripples of volume modulation.
Square Based on the 65 optical tremolo, but with a more aggressive, "chopped" tremolo sound.


Sets the overall effect output level. Use this control to make up for any perceived volume loss when a tremolo effect is active.


The footswitch toggles the effect on/off. The LED lights to indicate when the effect is active. The LED color changes to indicate the pedal settings for True and Buffered bypass and Tap mode, and the LED flashes at the current quarter note tempo rate.

Pedal mode LED colors

LED Color Bypass switch Tap switch
Green True On
Purple Buffer On
Orange True Off
Red Buffer Off


Bypass mode

You can switch between Buffered or True bypass modes using the slider switch on the back of the pedal. 

  • Buffer – The pedal's output is buffered. Use buffered bypass to minimize high frequency loss from long cable runs, and to preserve your tone when you have multiple pedals in series. 
  • True – The pedal signal is true bypass when the effect is off. 

Tap mode

You can configure the pedal so you can tap tempo with the footswitch, by setting the Tap switch on the back of the pedal to On. 

When tap tempo mode is enabled: 

  1. Tap once to activate the pedal, if it is bypassed. The pedal LED starts to flash at the current knob tempo.
  2. Tap twice to set a tempo. The LED flashes at the tempo you tap, and the effect plays back at twice that rate. 
  3. To bypass the pedal, press and hold the tap tempo switch until the LED turns solid, then release the switch. 

Tap mode notes

  • The tap tempo LED indicates the tempo in quarter notes, but the tremolo effects play back as eighth notes, so the effect sounds twice as fast as what you tap.
  • In Tap Mode, the footswitch bypasses the pedal when the switch is released, not when it is pressed. 
  • If you bypass the pedal with a tapped tempo, then activate the pedal again, the tapped tempo is retained, not the knob tempo.




UAFX Flow Specifications

Note: All specifications are subject to change without notice.

Power requirements

(power supply sold separately)

Isolated 9VDC, center-negative, 250 mA minimum
Inputs ¼” unbalanced TS
Outputs ¼” unbalanced TS
Input impedance 1 Megohm
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


(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)

0.62 lbs

0.28 kg



UAFX Flow 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, 250 mA minimum, 2.1x5.5 mm barrel connector. Additional details at


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.
  • This equipment does not contain a fuse or any other user-replaceable parts.
  • A compliance marking label is provided on bottom of the unit.

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 all instructions in the instruction manual.)


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