Post Go back to editing

SigmaStudio Tree ToolBox: No Slew, Clickless HW Slew, Clickless SW Slew in many categories

Hi Team,

I am using SigmaStudio 4.6 for ADAU1452.

In the Tree ToolBox window, there are

1) No Slew

2) Clickless HW Slew

3) Clickless SW Slew

three selections appear in some algorithm categories.

For example,

1) Volume Controls -> Adjustable Gain -> No Slew -> Single Volume

2) Volume Controls -> Adjustable Gain -> Clickless HW Slew -> Single Volume

3) Volume Controls -> Adjustable Gain -> Clickless SW Slew -> RC Optimized -> Single Volume

What are the differences of "No Slew", "Clickless HW Slew", and "Clickless SW Slew" categories? Where can I find more detail explanations of them?



  •      Hello,

         Slewing slows down parameter transitions.  For example, a slew volume control responds slowly to a sudden change of its setting, compared to an instant change for a non-slew control.  Slewing helps to minimize audible clicks whenever an adjustment is made.

         SigmaDSPs have always had software slewing -- where SigmaStudio incorporates the slewing algorithm into the running DSP code.  The Sigma300 DSPs like the ADAU1452 can also offload slewing to their new hardware slewing engine.  The idea is not necessarily to save instructions, but to provide a wide range of slew responses.  Thus, with your ADAU1452, many categories of adjustable functions are available with no slew, SW slew, and HW slew.

         The Wiki is the first stop for SigmaStudio algorithm info.  You'll find a list of articles for the volume controls here:

    Especially for the newer chips, documentation has not always kept up with advances in SigmaDSP performance.  Thus, sometimes it has been necessary for SigmaDSP users to experiment with new features -- documenting them as they go.  An example I did is here:

    Searching the forum will turn up other posts related to slewing.

         The adjustment of a volume control in your project can be done by any of these means:

    • moving the slider of a GUI volume control in SigmaStudio
    • Safeloading (from a microcontroller) the volume control's parameter word
    • Changing the value of the control input to an Ext Slew Volume control

    Any of these can cause undesired noises when non-slew controls are used, so slewing is nearly always preferable.  In fact, you'll notice that a non-slewing Ext Volume Control isn't provided in the Toolbox -- because such a function could be obtained with a simple multiplier from the Arithmetic section.

         Best regards,


  • Hi Bob,

    Thanks for your quick answers.

    But what is the meaning of "Clickless"?



  • Hello Ping,

    When you change the gain in steps that are too large you will hear clicks. This is often called "zipper noise". Using Slew will make many small steps between the larger steps so that you will not hear any clicks when changing the gain.

    Dave T