JAX Stereo Tool (AU‪)‬ 4+

Visual Stereo Audio Processor

Jens Guell

    • 4.7 • 22 Ratings
    • $9.99



Visualize and correct your stereo images.
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JAX Stereo Tool is a visual Audio Unit plugin for manipulating the stereo image of digital audio. The distribution app comes with an embedded plug-in (Audio Unit) that is available system-wide when you install the app. You should be able to use it with most supporting host applications.

Audio Units are Apple's recommended method for providing shared audio effects for applications and audio editors. You can load the plugin into any host application that supports at least stereophonic audio effect plug-ins (in Audio Unit format) with its own user interface.

JAX Stereo Tool has its main use as a mastering effect, that allows you to modify the stereo image of your audio by narrowing or widening it in a controlled manner. That is, the stereo output can be continuously adjusted in the basic function of pure mono to very wide stereo. This happens in real time and you can observe the result with the integrated correlograph, controlling and optimizing the audio thanks to this helpful additional visual information.

One of the special functions of JAX Stereo Toolis to recover lost mono-compatibility. This technique is conceptually quite simple and effective but somewhat difficult to understand. Please read the manual for further details.

The manual is shipped with the app or available on the product website.

What’s New

Version 2.3

2.3 (third maintenance update)

IMPORTANT: the type of the audio unit has been changed to provide MIDI support ('aumf'). existing projects possibly must be updated to access the new AU type.

A: ui improvements

- the user interface was completely reworked to provide much better contrast adjustment and readability and to fix some glitches with zooming and moving. the main controls now additionally give visual feedback, if tapped.

B: the contrast overlay controls can be hidden/revoked by a one finger long press gesture

- sometimes the ui moved around while adjusting the contrast with the slider. we fixed this.

C: AUM parameters

- the parameters are now specially exposed to the the AUM host app. the publishing of the main parameter (stereo width) disappeared therefore, because of the AUM MIDI type menu.

D: MIDI parameters

- the type of the audio unit was changed to support MIDI automation directly. the parameters stereo width, panorama and also volume can be automated with the standard continuous MIDI controllers 11, 10 and 7 now. The distribution app therefore got some new buttons to establish MIDI connectivity.

E: parameter interpolation

- users possibly want to dynamically automate volume, stereo width and panorama. so we implemented parameter smoothing for these realtime parameters to prevent zipper noise with automation. Especially MIDI automation requires parameter ramping, because MIDI values are usually quantized to merely 128 raw values per controller.

- note: some parameters (sample offset and all switches) are not thought for realtime automation and still may produce clicks or zipper noise when tweaked. this lies in nature of things and would require too much effort and advanced techniques to fade between states, which is not the purpose of this audio unit.

F: new bezier mode

- the correlograph can be toggled between points cloud and bezier mode. the bezier mode requires much more performance. so it is tagged as "experimental". while latest Apple devices should have enough power to run it, some older devices probably will make the UI stuck, while it is on. it was not even easy to get the points cloud to perform acceptably.

- if you do not use the graphs permanently, we recommend to switch it off, as this significantly improves entire graphics performance and reduces CPU usage.

G: the phase shift display was fixed to reflect the correct sample offset count and corresponding milliseconds value dependent of the current active samplerate.

H: the graph is now always proportionally resized with the plugins interface. the previous sizing was independent of the main ui, confusing some users.

Ratings and Reviews

4.7 out of 5
22 Ratings

22 Ratings

Tenente ,

Great stereo width/pan control

There’s plenty of stereo-izers or panning apps out there, the functions on this work best for me. This is the the last piece of my mixing, regardless of tremelos, automated panning, etc, this is the app I use to put the final stereo/panning on each track of a project.

houzcat ,

Does not appear as AUv3 on iPad

I bought this to use on my iPad Air (using iOS 12.4.9), which it said would work on this device, but when I open up GarageBand it does not appear as an audio unit nor in inter-app audio nor as a plugin effect. Nothing I can do to get it to show up in any of these effects slots. Basically was a waste of money, which is sad because these JAX products work fine on my iPhone SE :(

Nogreatcrime ,


This might be the worst UI i have ever seen.

App Privacy

The developer, Jens Guell, has not provided details about its privacy practices and handling of data to Apple. For more information, see the developer’s privacy policy.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

    Up to six family members can use this app with Family Sharing enabled.

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