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Sigma DSP volume control implemented using dither?

SigmaDSP & SigmaStudio Torch Jan 10, 2014 00:00 3 replies Original on forum ↗
Thread Summary

Thread Summary

The user inquired about the implementation of dither in Sigma DSP volume control. The final answer clarified that dither is not implemented in the volume controls, but a 24-bit word provides high gain accuracy. For dithering, the user can manually add a white noise generator, scale it, and mix it with the audio. The user sought further clarification on noise shaping and Triangular PDF, but only white and pink noise are supported.
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Torch Question
Jan 10, 2014 00:00

Hi,

Can anyone advise if the Sigma DSP volume control is implemented using dither and, if so, what type of dither is used?

Many thanks

SigmaDSP

ADIApproved Reply
Jan 10, 2014 00:00

Hi Torch,

Dither is not implemented on the volume controls. Keep in mind that since you have a 24-bit word controlling the volume, this gives you an accuracy of 0.000001 dB in the amount of gain you can apply.

If you would like to implement simple dither with white noise, you can use a white noise generator from the library, scale it appropriately using a gain cell, and then mix it with the audio.

Torch Reply
Jan 13, 2014 00:00

Hi Brett,

Thanks for the clarification.

I did not understand the relevance of the accuracy of the gain that can be applied. My concern is the truncation error when outputting a 24-bit signal (e.g. in the ADAU1445 ) especially when the gain effectively reduces the signal to 16 bits or less.

Is there any support for Triangular PDF or noise shaping rather than the Gaussian PDF of white noise?

Many thanks

ADIApproved Reply
Jan 15, 2014 00:00

The only noise functions we have available are white noise and pink noise. No noise shaping functions are available, unfortunately.