






Table Of Content
Introduction
Description
Blue Cat's Protector is a 0dB stereo brickwall limiter with adjustable dynamics response. It will typically find its place on the master bus of your DAW to protect your audio output from overshoot, limit the general volume and improve the perceived loudness, thanks to a very transparent frequency response.
Despite its very simple set of controls, it offers a wide range of sounds and it is also suitable as a track limiter for more creative effects such as distortion, pumping or heavy limiting.
Beyond its powerful dynamics processing features, and like most of our plugins, Blue Cat's Protector also offers a powerful side chain capability thanks to its MIDI CC output. This unique technique not only lets you do side chain limiting but also parameters modulation: control any parameter of any plugin to create powerful side chain effects in real time.
If you are looking for a complete dynamics processing solution you might be interested in looking at Blue Cat's Dynamics plugin.
Typical applications: master limiting, loudness maximizing, distortion, clipping.
Main Features
- 0 dB brickwall peak limiter and waveshaper.
- Continuous control of the dynamics response from transparent limiting to colorful distortion.
- Stereo link control.
- Large audio levels and gain reduction meters for optimal monitoring.
- Side chaining capability: a unique way to perform side chain compression and much more.
- Plugin window transparency management.
- No latency.
- Supported platforms: Mac-AU, Mac-VST, Windows-DX, Windows-VST.
- Native DSP code for optimal performance.
- Skinnable user interface.
- Smooth Update: silent (zipper-free) parameters update.
- Full automation support (all parameters can be automated, with smooth and continuous update)
- No CPU load on idle: when the plugin is fed with silence, the processing smoothly shuts down, to optimize the CPU usage of your Digital Audio Workstation.
- Real time MIDI control with advanced settings (MIDI channel and CC numbers, with complete response curve control) and MIDI learn.
- Automation and MIDI output: record output parameters as automation curves or send MIDI CC messages to other plugins for powerful side chain effects.
- Smooth Bypass: activate/deactivate the plugin with absolutely no noise.
- Undo/Redo.
- Import/Export presets in a host independent format.
- Any sample rate supported.
System Requirements
PC
- Microsoft Windows XP, Vista or Windows 7.
- Any DirectX / VST compatible host software .
Mac
- An Intel or PowerPC processor.
- Mac OS X Leopard (10.5) or Snow Leopard (10.6).
- Any VST / Audio Unit compatible application.
For more information about supported platforms, see our FAQ.
Installation
Blue Cat Audio plugins cannot be run standalone, they require a host application (see the System Requirements chapter for more information). Depending on which host application you use, you might need to install the plugins in different locations.
Windows
Install
Both DirectX and VST versions provide an install program. Follow the steps of the wizard to install the plugin on your machine. During the installation you will be asked where you want the plugin(s) to be installed. For the VST version you should install the plugin inside the VST plugins folder used by your host application(s). The default path set in the installer should work for most applications, but you should check your host software documentation to know where it looks for VST plugins.
Some applications will not automatically rescan the new plugins, so you might have to force a refresh of the plugins list.
Upgrade
When a new version of the plugin is released, just launch the new installer: it will update the current installation.
Mac
Install
On Mac the plugins are available as drive images. After download, double click on the file to open it. You can then drag and drop the plugin file(s) to the shortcut that is provided within the image. It will install the plugin(s) for all users on the machine.
In case you do not have admin rights on your Mac or if you want to install the plugin(s) to another directory, just copy the files to the appropriate location. If required, more information is available in the README.txt file that is included in the package.
Upgrade
When a new version of the plugin is released, open the new image and copy the files over the previous ones. The new version will replace the older one.
Using Blue Cat's Protector
The User Interface
Blue Cat's Protector is bundled with a single skin, but you may create your own and download new ones on our web site: Blue Cat's Protector skins. The main controls offered by the plugin are the following:
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The various elements of the user interface (knobs, sliders, button...) are simple and intuitive to operate, but more information about how to interact with them is available in the "Plugins Basics" chapter of this manual.
Operation
The limiter has very few parameters but they let you precisely control the dynamics response if you understand them well. Short descriptions of these parameters are available in the parameters section. We will give you here more details about their influence on the sound and the way it is processed.
Controlling the Limiting Effect
By default, the limiter has a fixed input threshold of 0dB. You can control the input level with the Pre-Gain knob to adjust the input if it is too loud or quiet. Every peak above 0dB will trigger a gain reduction to reach the 0 dB peak level. You can then adjust the output gain to the desired level: the the output peak level is guaranteed to be maintained below the chosen output level.
The “knee” parameter offers a way to obtain a smoother limiting effect: it adjusts the shape of the gain reduction curve. The limiter will start its gain reduction before the signal reaches 0dB (precisely at 0dB minus the knee value), with a smooth and continuous curve:
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Default response (no knee)
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Response with large knee value |
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When the knee is set to its maximum value (30 dB), the limiter offers an extra 6dB overhead to the input level. This means that the input signal can reach +6dB before it actually hits the final brick wall. On the other hand, limiting will occur before the audio level reaches 0dB, as you can see on the graph above.
Reaching Distortion
When the release time reaches very low values (less than 10 ms), a great amount of distortion will occur. At 0 ms Blue Cat's Protector acts as a wave shaper and clips the audio signal.
Again, with the knee parameter you can adjust the shape of the wave shaper from digital hard -clipping (knee=0dB) to soft analog-like saturation (knee=30 dB).
True distortion can be achieved by increasing the input level to force continuous clipping of the audio signal over time (instead of only clipping the peaks). The larger the input gain, the larger the distortion. It is possible to cascade several instances of the plugin in order to achieve a very large amount of distortion.
Level Maximizing
A common task for a brickwall limiter is level maximizing: you can increase the perceived loudness of an audio recording without changing its peak level.
Depending on the type of media your recording is targeted to (mp3, CD, ...) and your host application, you might need to adjust the output level to less than 0dB (typically -0.1 dB) in order to avoid peak distortion.
Once the output level has been set, start with a 0dB knee value. Increase the input gain until you can hear artifacts on the output (typically a few clicks on heavy transients). Increase the knee value until you cannot hear the artifacts anymore: you have reached the optimum settings!
Another important setting for this task is the release time: you will typically keep it quite high to avoid too fast volume variations.
Note that you can also cascade several instances of the plugin in order to increase further the perceived loudness.
Side Chain Capabilities
Thanks to its MIDI CC output, Blue Cat's Protector will let you perform side chain limiting and create your own volume controlled effects in a few mouse clicks. For side chain limiting, you will also need to download Blue Cat's freeware gain plug-ins.
In order to use the real time side chaining functionality of Blue Cat's Protector, do the following:
- Create a new bus in your project and send the audio source track (the audio track used as control signal for the side chain)on it.
- Insert Blue Cat's Protector on this bus.
- Insert Blue Cat's Gain on the destination track (mono or stereo).
- Assign the Comp (Comp(L) and/or Comp(R)) output parameter to a given MIDI channel and CC number.
- Assign the Gain parameter of the Gain plug-in to the same MIDI channel & CC number as the Total Gain.
- Route Blue Cat's Protector MIDI output to Blue Cat's Gain MIDI Input.
Blue Cat's Protector will now control the Blue Cat's Gain plugin depending on the audio source input level.
If you have issues performing the above tasks in your host application, please visit our website and check our step by step tutorials that explain how to use the MIDI CC i/o features in various host applications.
Blue Cat Audio Plugins Basics
This chapter describes the basic features that are common to all our plugins. If you are already familiar with our products, you can skip this part.
User Interface Basics
About Skins
Like all Blue Cat Audio plugins, Blue Cat's Protector uses a skinnable user interface. It means that the appearance and behavior of the user interface can be entirely customized.
Especially with third party skins, the experience may be very different from the one offered by the default skins that we provide and which are described later in this manual. Our plugins and our skinning engine however have several standard features that will be available whatever your favorite skin. This is what this chapter will describe.
More information about custom skins can be found in the skins section.
Main Toolbar and Menu
Menu
If you right click on the background of the plug-in, the following pop-up menu appears:

The description of the commands associated to each menu item are available below.
Toolbar
In some skins, an optional toolbar gives you access to the some of the functionalities of the main menu.
| Icon | Name | Function |
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Menu | Open the main menu |
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Undo | Undo |
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Redo | Redo |
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Load | Load Preset |
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Save | Save Preset |
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Manual | User Manual |
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About | About |
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Website | Opens our website |
Commands
The Commands available from the main menu or the toolbar are:
- Set Preset Skin: change the skin for the current preset.
- Use Global Skin: use the skin defined in the global settings for the current preset. This item is enabled only if a skin has been defined for the current preset.
- Undo/Redo: undo or redo the latest modifications. This includes all changes made to the current preset settings.
- Load Preset: load preset from file.
- Save Preset: save current preset to file.
- Presets Settings: open the presets settings window. It enables you to change the skin and MIDI settings for the current preset.
- Global Settings: open the global settings window. It enables you to change the skin and MIDI settings that are used by default in all instances of the plugin.
- User Manual: open this user manual.
- Check Updates: check the updates for this software on our website.
- Get More Skins: get more skins for this software.
- About: displays the “about” dialog box.
MIDI control
Blue Cat's Protector can also be remotely controlled via MIDI using MIDI CC ("Control Change") messages if your host application supports it. It is possible to customize the channel, control numbers and range used for each parameter in the MIDI settings panel available from the main menu (see the Plugin Settings chapter for more details).
Controls
Examples
Here are a few examples of typical controls you will encounter in the user interface of our plugins:
| slider | slider | knob | button | Text control |
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Interacting with Controls
You can interact with the controls of the plug-in interface either with the mouse or the keyboard.
Setting the keyboard focus on a control (so that it reponds to key strokes) may be automatic (when you pass the mouse over it it gets focus) or manual (you have to click on the control to set the focus on it). Note that all host applications behave differently regarding keyboard handling. In some applications you may not be able to use all keys described later in this manual to interact with our plugins. It is usually made obvious to you to know the active surfaces of the skin (the places where you can click with the mouse): the mouse cursor usually changes when you can do something on a control. In the default skins delivered with the plug-in, the cursor changes to a small hand or an arrow to tell you when your mouse is over an active control.
Mouse
Various mouse movements will let you interact with the controls:
| Mouse Interaction | Action |
|---|---|
| Left Click | Acquire focus and start dragging or push (button) |
| Left Click + Alt Key | Set the value to default |
| Left Double Click |
Acquire focus and launch the “fine
tuning” edit box (except button):
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| Right Click | Set the value to default |
| Mouse Wheel | Increment or decrement the position (focus required) |
| Mouse Drag | Change the control position depending on mouse movement (except button) |
Keyboard
All control widgets support the following keys (note that some of them are caught by the host and thus never forwarded to the control. For example in Steinberg Cubase SX you cannot use the arrow keys to control the plugin):
Keys Common to All Controls
| Key | Action |
|---|---|
| Up Arrow | Small increment of the position (up or right) |
| Down Arrow | Small increment of the position (down or left) |
| Left Arrow | Same as Down Arrow |
| Right Arrow | Same as Up Arrow |
| Page Up | Large increment of the position (up or right) |
| Page Down | Large decrement of the position (down or left) |
| + | Small increment of the value of the control |
| - | Small decrement of the value of the control |
| d | Set to default value (same as mouse right click) |
| e |
Opens the 'fine tuning' window to precisely
set the parameter:
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| SHIFT | When the key is down, the fine tuning mode is on, and you can modify the value with better precision when moving the mouse, the mouse wheel or using the keyboard. Just release the key to get back to the normal mode. |
Keys Specific to Buttons
| Key | Action |
|---|---|
| Enter | Pushes the button |
More
Check our online tutorial for more screenshots and more examples of our plugins user interfaces.
Blue Cat's Protector Parameters
All parameters described below can be automated and controlled via MIDI if your host application supports it. You can precisely define this behavior in the settings panels described later in this manual.
The plugin exposes both input and output parameters to let you both control and monitor the behavior of the plugin:
Input
| Param id | Name | Unit | Description |
|---|---|---|---|
| dsp.input0 | Bypass |
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Bypass the effect. |
| dsp.input1 | Pre | dB | Input gain, before the limiting stage. |
| dsp.input2 | Release | ms | Release time for the limiter. Controls how fast the limiter reacts to volume drops. Set the release parameter to 0 for distortion. |
| dsp.input3 | Knee | dB | Controls the softness of the limiting: the higher the value, the softer the limiting. Limiting starts at 0dB minus the knee value. See the usage section for more details. |
| dsp.input4 | Link | % | Link the left and right channels gain. At 0% both channels work independently, and a 100% the same gain reduction is applied to both channels. This lets you control how the stereo balance is affected by the limiter. |
| dsp.input5 | Max Reset |
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Reset the max compression values (see output parameters). |
| dsp.input6 | Post |
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Output gain, after the limiting stage |
Output
| Param id | Name | Unit | Description |
|---|---|---|---|
| dsp.output0 | Pre Peak (L) | dB | Audio input level for the left channel. |
| dsp.output1 | Post Peak (L) | dB | Audio output level for the left channel. |
| dsp.output2 | Comp(L) | dB | Amount of compression (instant) for the left channel. |
| dsp.output3 | Max Comp(L) | dB | Maximum amount of compression for the left channel. Can be reset by changing the “Reset Max” parameter. |
| dsp.output4 | Pre Peak (R) | dB | Audio input level for the right channel. |
| dsp.output5 | Post Peak (R) | dB | Audio output level for the right channel. |
| dsp.output6 | Comp(R) | dB | Amount of compression (instant) for the right channel. |
| dsp.output7 | Max Comp(R) | dB | Maximum amount of compression for the right channel. Can be reset by changing the “Reset Max” parameter. |
Note: the param id field is used when designing a new skin. See the skins section of this manual for more information.
Plugin Settings
In addition to the controls offered in the main user interface, Blue Cat's Protector has various settings that let you fine tune the behavior of the plugin. You can choose to change these settings either for the current preset or globally for all instances of the plugin.
The Global Settings Window
The settings available in this window apply to all instances of the plug-in, for all presets. Consider these settings as “default” settings.
Global Skin
You can change the default skin for all instances of the plug-in: write the skin file path in the text edit box or click on the button to open a file chooser dialog. If you have several instances of the plug-in opened in your session, you will have to re-open the user interfaces of these plug-ins to see the skin change.

Global MIDI Input Settings
For each parameter you can define a default MIDI channel and CC number. You can then control the plug-in with an external MIDI controller or one of our plug-ins that generate MIDI messages.
The following settings are available for each plug-in parameter:
- Channel: MIDI Channel for the parameter control. If set to 0, the plug-ins will accept Control Change Messages from all MIDI Channels (MIDI Omni mode).
- CC: Control Change Number.
- Learn: click on this button to activate the MIDI learn functionality. When it is activated, you can move your MIDI controller, and the plug-in will automatically set the MIDI Channel and CC Number.
- Enable MIDI: enable/disable the MIDI control of the parameter.
- Response: response curve of the MIDI control: from very fast to slow control.
- Min: minimal value of the parameter when MIDI controlled.
- Max: Maximum value of the parameter when MIDI controlled.

Note: if the Min value is higher than the Max value, the response curve will be reversed: increasing the MIDI controller value will decrease the parameter value.
Note: if you double click on the parameter text control boxes for the max and min values, a “fine tuning” edit box will appear and let you change the min and max values with more precision:

Global MIDI Output Settings
You can set the same properties for the output parameters: they may trigger MIDI CC messages when modified. Since it's output, you cannot set the channel to MIDI Omni, you must choose a channel:

Note: if the Min value is higher than the Max value, the response curve will be reversed: increasing the MIDI controller value will decrease the parameter value.
Note: if you double click on the parameter text control boxes for the max and min values, a “fine tuning” edit box will appear and let you change the min and max values with more precision:

Global Automation Output Settings
If your host application does not let you choose which parameters to record as automation curves, you may need to choose the automation enabled parameters in the plugin itself. In this pane you can decide which output parameters of the plugin will record automation, for all instances of the plugin:

All parameters are enabled by default. Click on the check box to enable/disable automation for a parameter.
The Current Preset Settings Window
This window lets you change the settings for the current preset of the current plug-in only.
Preset Skin
You can choose to use the global skin setting or to change the skin for the current preset. This way you can have different skins for different instances of the plug-in in the same session in order to differentiate them.

Preset MIDI Input Settings
Use the global settings or override them for the current preset. The parameters are the same as for the global MIDI input settings.

Preset MIDI Output Settings
Use the global settings or override them for the current preset. The parameters are the same as for the global MIDI output settings.

Preset Automation Output Settings
Use the global settings or override them for the current preset. The parameters are the same as for the global automation output settings:

About Skins
Blue Cat's Protector integrates Blue Cat's skinning engine that allows you to customize the user interface. You can download new skins for your plug-in at the following address:
If you don't find a skin that fits your need or if you want a really custom one, you can choose to create your own skin.
Changing the Skin
You have two ways to change the skin of your plug-in: you can change the default (or 'global') skin in the global settings, or change the skin for the current preset only (either in the preset settings page or from the main menu). The global skin applies to all plug-in instances, whereas the current preset skin only applies to the current preset of the current plug-in instance.
See the main menu for more information abour how to access these options.
On some hosts the plug-in window won't resize automatically when you choose a skin with a different size. In this case, just close the window and re-open it: it will be displayed with the right size.
Create a Custom Skin
You can create custom skins for your plug-in in order to adapt it to your exact needs. You can change its look and feel and make it completely integrated in your virtual studio!
Just read the Blue Cat's Skinning Language manual and download the samples for the tutorial on http://www.bluecataudio.com/Skins. You can get ready to create your own skins in a few minutes.
You can then share your skins on our website.
FAQ
Automation Output
MIDI Output
Plug-ins Formats
Here is a list of host software and the version we recommend you to use. Many other applications are supported, check your application user manual to choose the best version (AU stands for "Audio Unit" and DX for "DirectX"):
| Host Application | Plug-in Version |
|---|---|
| Cakewalk Products (Sonar, Project5...) | DX |
| Sony Products (Vegas, ACID, Soundforge) | DX for old versions, VST for new |
| Steinberg Products (Cubase, Nuendo, Wavelab) | VST (Mac or PC) |
| Ableton Live | VST (Mac or PC) |
| Adobe Audition | any |
| EnergyXT | VST |
| Magix Samplitude | VST |
| Digidesign Pro Tools | RTAS if available, any otherwise (RTAS adapter required) |
| Apple applications (Logic Pro, Logic Express, Garage Band...) | AU |
| ... |
Installation
Most software you can purchase on this website is plugins for host applications. It means you need another application to use it. See the "Plugin Formats" section in this FAQ for more information.
First check that you application supports DirectX, Audio Unit or VST plug-ins.
If you are using the DirectX version, check that your host application supports DXi plug-ins (MIDI enabled DirectX plug-ins). If it does not, it may remove it from the DirectX plug-ins list (some applications such as Sony Vegas 5 and Cool Edit Pro are known to do this). In this case, use our DXi Manager free utility and disable the MIDI capabilities of the plug-in. You may need to reinstall the software again before it shows up into your host application. For more information about this topic please read our DXi in Sony Vegas tutorial (it is applicable to other applications than Sony Vegas).
If you are using the Direct X version and your host application supports DXi, check that the plug-in does not appear in the 'virtual synth' or 'synthesizers' category. If you wish not to use the MIDI capabilities of the plug-in and use it as a regular Direct X plug-in, you can download the freeware DXi Manager and disable the MIDI capabilities of the plug-in.
Our plugins require several additional files for default settings, skins and miscalleanous data. We provide an installer for our customers convinience. Our installers do not modify the system settings settings or the Windows registry, except for the DirectX versions registration. Our installers won't harm your system.
Software Version
Upgrade
Automation
More...
This manual only covers the basics of Blue Cat's Protector. Our website offers many additional resources for your Blue Cat's Protector plugin and is constantly updated, so keep an eye on it! You will find below a few examples of available resources.
Extra Skins
We encourage our customers to propose their own skins for our products and we often propose alternative skins to let you choose the one that best suits your needs. You can check Blue Cat's Protector skins page to get the latest skins.Landscape
![]() | Product: Protector Description: A landscape layout skin for those who prefer horizontals to verticals. Author: Blue Cat Audio Download: Skin_Landscape.zip |
Bronze
![]() | Product: Protector Description: An alternative design with a layout close to the original skin. Author: Limeflavour (www.flavoursoflime.blogspot.com) Download: Skin_LimeFlavourBronze.zip |
Tutorials
Many Tutorials are available on our website. They cover a wide range of topics and host applications. You will find below a list of tutorials that are related to the Blue Cat's Protector plugin. An updated list is also available online.
Tutorial - Using DXi plug-ins in Sony Vegas
![]() | This tutorial will teach you how to use any DXi plug-in in Sony Vegas: Sony Vegas does not support MIDI automation, so if your plug-in supports the MIDI Dxi protocol, it is removed from the plug-ins l...[Read More...] |
Tutorial - Export Plugin Presets to Share them with the Community
![]() | This tutorial shows you how to export your presets in order to share them with the community on the Blue Cat Audio website. This tutorial uses Blue Cat's Stereo Triple EQ for the demonstration bu...[Read More...] |
Tutorial - Getting Started with Plugins User Interface
![]() | Get used to the user interface features of Blue Cat Audio products! They have been designed for an optimal workflow, so here are the tips and tricks to save time. All these functionalities are explain...[Read More...] |
Tutorial - Using MIDI Control in Sonar
This tutorial will help you understand how to use parameters MIDI control in Cakewalk Sonar. It is applicable to any DXi plug-in (MIDI enabled DirectX plug-in)....[Read More...] |
Tutorial - Using MIDI Connectivity in a Modular Host (Plogue Bidule)
![]() | This tutorial shows you how to use the MIDI connectivity of our plugins in a modular host such as Plogue Bidule. We are using the Mac version of Bidule in this tutorial. The scenario here is very sim...[Read More...] |
Tutorial - Using Blue Cat Audio plugins connectivity in Reaper
![]() | This tutorial shows how to use our plugins MIDI connectivity within Reaper. We use Blue Cat's Dynamics plugin as an example, but you can use any other audio plugin which provides output parameters, su...[Read More...] |
Tutorial - Connecting plug-ins together in Logic for advanced side chain effects
![]() | This tutorial shows how to use the connectivity capabilities of our plugins within Logic. We use Blue Cat's Peak Meter Pro plugin (DPMP) as an example, but you can use any other audio plugin which pro...[Read More...] |
Tutorial - Using Blue Cat Audio plugins connectivity in Pro Tools
![]() | This tutorial shows how to use the MIDI connectivity of our plugins within Pro Tools. We use Blue Cat's Peak Meter Pro plugin as an example, but you can use any other audio plugin which provides outpu...[Read More...] |
Tutorial - How to Use the Free Presets Available on this Website
![]() | This tutorial shows you how to get and load free presets for your favorite Blue Cat Audio plugin. This tutorial uses Blue Cat's Dynamics for the demonstration but is applicable to all our plugins...[Read More...] |
Updates
As you can see in the history log below, we care about constantly updating our products in order to provide you with the latest technology available. Please visit often our website to check if Blue Cat's Protector has been updated, or subscribe to our Newsletter to keep you informed with the latest news about our products.
Versions History
See you soon on www.bluecataudio.com!













