ADAU1467 Ext vol + AUXADC input= -87Db max

Hello Sashkashka,

The AuxADCs on the Sigma 300 / 350 DSPs output a level from 0 to integer 1023 depending upon the input from your potentiometer. 1023 in the integer (32.0 format) works out to 0.0000002382 decimal -- which explains the huge attenuation even with the pot fully CW. You could fix this by adding a lot of gain between the AuxADC and the Volume Control, yet a more elegant way is shown below:

The gain of (1/32) reduces the AuxADC range to 0-31 (1023/32 = 31.97, and integer arithmetic rounds down). This goes into the Lookup Table which assigns a dB level to each integer input. If you download the attached project you can open it in SigmaStudio and click the Table button to see the LUT's contents. The result is a full volume range. The Level1 meter shows a -3dB reading because it's RMS responding while 0 dB full scale is defined as reaching +/- 1.0 decimal peaks.

Best regards,

Bob

1467-LUT-vol.zip

Hello Sashkashka,

Bob's solution will give you a lot of control of the volume range and the curve as well. If you are seeking a simpler way you can simple shift the ADC data before going to the volume control like this:

This will left shift the 10 bit output of the ADC that is right justified to be a 1.24 number. This will give you a larger range going from almost "1" to a very low gain. Usually this is down into the noise floor. I have run into issues where the debounce block might not let it go down to zero, or there is noise on the ADC input, then you might still hear the signal way down into the noise floor when the pot is at minimum. There are ways to get around that if needed but most applications this simple method works well.

If you need more control then Bob's method with the table will give you full control.

Dave T

Hello! An amazing solution! Thanks!

Hello! Thank You very much!