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Product TB FlX
Developer ToneBoosters
Price (MSRP) € 19.95
Type / Tags
Plug-in, App & Soundware Format(s)
Operating System Availability
Download Released
 3.0.5  Downloads Released
 3.0.5  Downloads Released
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Equalizer sections and filter types

TB FlX ("Flex") combines equalization and dynamics processing in one go. It works just as most equalizers; it has 6 filter sections with lots of controls to modify their effect on the spectrum. More than 30 filter types are currently supported, which include classic analog peaking and shelving filters and resonating low- and high-pass filters. Besides these conventional filter types, some not-so-common or entirely novel filters are available as well:

  • Bell-shape filters that have a flatter top than analog filters, to give a more natural sound;
  • Non-resonating shelving filters to allow for steeper filter slopes;
  • Gaussian filters, because these filters have the shortest possible group delay;
  • Gammatone filters, because they closely mimic the frequency analysis of our hearing system;
  • Linear and logarithmically-spaced harmonic filters, for creative effects;
  • Brick-wall highpass, lowpass, and bandpass filters;
  • Analog resonating highpass and lowpass filters (order between 1 and 16);
  • Analog bandpass filter;
  • Spectral balance filter;
  • and several more.

In the unlikely case that you want to create a filter shape that is different from any of the included ones, TB FlX supports a so-called 'auto node link' mode. In this mode, the filter shapes will be automatically constructed such, that their combined effect will give a smooth, interpolated curve through all nodes that were configured as 'auto node link' filter.

Each filter section has its own 'amount' control to modify how much of that filter is actually applied to the audio signal. Furthermore, the filter can be applied in stereo, left only, right only, mid only or side only channels.

Linear phase or minimum phase?

We have closely followed the sometimes intense debates on minimum phase and linear phase equalizers, and the pros and cons of each of them. We understand that you appreciate the surgical editing precision of linear phase, and the snappy, accurate time response with minimum pre-ringing of minimum phase. Wouldn't it be great if these benefits could be combined in one algorithm, without the cons?

TB Flx has the potential to solve the minimum vs linear phase debacle for once and for all by introducing 'auto phase'. The phase response of the equalizer is dynamically adjusted to give the best of both worlds, adapted to the input signal and the desired equalizer curve.

Dynamics processing without limits

Each filter section also has a dedicated dynamics processing (compressor) stage. This means that a filter response can become more or less active depending on the input signal level. The compressor input/output curve is configured by dragging nodes in an input/output graph. This way, the input/output curve can be configured beyond what is possible with conventional compressors using threshold and ratio controls. Expansion, downward compression, upward compression, positive or negative ratios, parallel compression, New-York style compression (via the 'amount' control) are all easy to set up, and can be configured for each filter section independently. Of course you can set the attack and release times, and an auto-release (AR) function is supplied as well.

The level detector of each compressor section also has some innovative features. Besides being able to respond to stereo level changes, the level detector side chain can also operate on mid only, side only, left or right only, and even on the side-over-mid ratio.

Putting it all together

All user-accessible and internal parameters are interpolated automatically with maximum precision, using 4 times oversampling. This gives ultra-smooth, zipper-noise free behaviour for no-compromise, professional-grade output quality. And did we mention the integrated DC-reject filter (DCF)?


  • More than 100 parameters to shape the sound in a clean and simple interface.
  • 6 filter sections with many controls to modify their behavior;
  • More than 30 filter types, including a unique 'auto node link' filter type.
  • 3-node dynamics processing editor for each filter section.
  • Manual and auto-release (AR) option.
  • Integrated output spectrum analyzer with zoom functionality.
  • Unique, innovative auto-phase filter mode for high-resolution transient response.
  • Based on the VST 2.4 specification to allow compatibility with virtually all host programs.
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Average user rating of 10.00 from 1 review

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