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License validity

License validity in short

Licenses are valid for life, including software updates. New features may cost extra, but you can always keep using the features that you bought in newer versions.

A license can be used by (whichever comes first):

  • One radio station (one streaming and/or FM instance).
  • One person, on at most 3 systems.
  • One pc with multiple users.

For more detailed info, read the right column.

More detailed info

Using Stereo Tool as the processor for a radio station
If you use Stereo Tool as the processor for a radio station, you need a separate license for each instance that you run. If you compare it with hardware processors: If you would need multiple hardware processors, you need multiple Stereo Tool licenses.


  • You can reuse the same license for testing, preset tweaking etc.
  • You can prepare a backup system with the same license, as long Stereo Tool is not running on both systems simultaneously all the time.

Using Stereo Tool for processing files or private listening
If you need to process files (for example because you're a music producer, jingle maker, voice over artist) the license is tied to you as a person, and you can use it on upto 3 computers (for example your home pc, office pc and laptop).

Alternatively, if you have computers that multiple people use, then you need a license for each such system.

What license do I need?

Some of the features are free, they don't require a license. Without a license there will be an occasional popup (once every few weeks), but no audio nags. These are features that are mainly aimed at people who just want to listen to music at home, not at professional use cases. The VST plugin always requires a license, because VST plugins tend to be used in professonal environments.


Basic, FM Standard or FM Professional?

If you don't use Stereo Tool for FM processing, Basic suffices.

FM Standard offers "standard" FM processing, stereo and RDS encoding. The processing in this license is comparable to what many high end hardware boxes offer. In most markets, this license will make you one of the louder stations on the dial.

FM Professional adds our special Composite Clipper to the processing. The Composite Clipper takes the stereo pilot, stereo encoding and RDS into account when generating the composite MPX signal, which increases the headroom for audio by several dB's. You can typically generate a signal that's 2-3 dB louder without sounding more clipped, which results in a much more dynamic and much higher fidelity signal. Beside that it unlocks our "Asymmetric L-R" mode, which adds another 1 dB or so. Beside these advantages to the audio signal, the clipper can also analyse the RF spectrum after the exciter, and optimize the signal to reduce reception issues in fringe areas and in multipath areas.

If you can use Stereo Tool to generate the composite MPX signal, we highly recommend the FM Professional version, which sounds much better and improves your reception. To be clear, with FM Standard you're not doing worse than most high end hardware boxes, but FM Professional really takes it to another level - assuming proper hardware you'll be the loudest and cleanest station on the dial.


Due to the so-called loudness war, where everyone wants their track to sound louder than any other track, nearly all music from the last 25 years or so has been clipped during mastering. This causes several issues:

  • It sounds distorted
  • It lacks dynamics
  • Low bitrate codecs are using a lot of their bits to encode the distortion, leading to much more lossy compression (MP3, AAC, ...) artifacts.

To make things worse, audio processing tends to boost softer sounds, in this case, the distortion, which worsens these problems. The Declipper repairs the audio before it enters the processor.

Our declipper is also used by police forensics labs. Check the video to see and hear how it fixes clipped audio.


The Delossifier improves the sound of lossy compressed audio. It's targeted at repairing low bitrate MP3 and MPEG2 files. Use this if your playlist contains low bitrate tracks. (But please, do everyone a favor and replace them.... With clipped audio that's usually not possible, but low bitrate is a different story.

Advanced Dynamics

Advanced Dynamics consists of multiple elements:

  • Auto EQ and Bass EQ
  • Speech detection, allowing different processing (less bass enhancements for example) for speech vs music.
  • Upto 4 AGC bands instead of 2
  • Dynamic attack and release times for all compressors and AGC
  • Progressive ratios for all compressors
  • Progressive release behavior for all compressors

Auto EQ adjusts the sound before the AGC without compressing it. This makes it possible to have a much more consistent output without sounding processed. Since it doesn't compress the audio, it doesn't add density and doesn't cause pumping or breating. Auto EQ can achieve the same spectral consistency that multiband compression can, without those side effects. It does not affect audio levels, only the spectrum. See the video on the right.

Dynamic attack and release times means that the speed at which the compressors and AGC act is adjusted based on the input. If the input is very dynamic, the speeds are increased, if the sound is already very constant, the compressors back down to not reduce the dynamics further. A sudden loud sound is handled gracefully, both when going down and when coming back up, to greatly reduce any audible gain riding.

Progressive ratios and makes it possible to have a different ratio in the compressors depending on how much they are pushing the level down. When it gets deeper, it gets steeper. So a very loud sound will be compressed more. Progressive release speeds up the release when the compressor is further down.

This video on the right shows the Auto EQ in action.