Digital volume control Adau1452

Hello. Recently I found great topic with digital volume control that may help with resolution decreasing in low volume values 

KJBob gave interesting algorithm for that in the topic here

Unfortunately, the topic in 7 y.o. and image attached by Bob is "optimized" in the server, so I can't see any node in order to repeat the project. Could anyone explain (perhaps Bob can remember) what nodes used in Sigma studio for that? 

Best regards, Alex

  • 0
    •  Super User 
    on Oct 24, 2020 6:03 PM 1 month ago

         Hello Alex,

         You can usually magnify any posted image by clicking on it.  Yet you need not re-create the project, I found it and have attached it below.  Yes it's nearly seven years old, apparently done with SigmaStudio v. 3.10 -- you can always find out which version made an old project by duplicating the project (for safety) and "opening" it with Notepad.  Among other things, this project has the old style DC Sources.  Yet it still opens and runs with SigmaStudio 4.5 and the 1452MINIZ board:

    Apparently the project was intended merely to demonstrate how audio which has been truncated down to a few bits could have its quantization noise slightly reduced through dithering.  The noise is quite evident through headphones, and activating the dithering signal does make a small difference.  I'm not sure if SigmaStudio v. 3.10 had the bit-shifting operations now included, and I had used multiple gains, a holdover from the ADAU1701 which handles decimal numbers only up to 15.999.  For what it's worth, here's the project file.

         Best regards,


  • Wow, you have a great archive with 7y.o. projects. Thanks, will explore it. Yes, I already try to click on the image in that topic, but magnified image has 562x172px resolution, which isn't enough to see details or even names and values of this nodes. Thanks for the project, again. 

    Best regards, Alex

  • 0
    •  Analog Employees 
    on Oct 26, 2020 3:39 PM 29 days ago

    Hello Alex and Bob,

    Great work Bob as usual. Slight smile

    I wanted to share an experience I had with a customer about a year or so ago. The customer shall remain nameless but they use the product to drive very high quality speakers with lots of amplification. The speakers are used in a well controlled acoustic environment built for listening. Since they were using the Sigma300/350 parts that have a great deal of headroom, 42dB, I suggested they raise the levels of signals coming in by like 20dB or more and then lowering it back before sending it out of the DSP. So all the filters and volume controls would have lots of bits of resolution below 0dBFS of the serial input and output ports. 

    I was expecting that they would be able to hear the granularity of the signal when the levels are set really low on the output. 

    So they tried it and reported back that it made no discernable difference. These guys have well trained ears so I trust their findings. So they did not do the gain shift internally. This is a case of where the theory says it should make a difference but in practice it did not. 

    I teach some as an adjunct professor at a couple of recording schools and one of the examples I state when talking about specifications of audio gear is this.  In theory, if you put a bag of potato chips in the front seat of your car your fuel mileage will go down. It is simple physics, you add mass it will take more energy to move the car.  In practice this difference is swamped by MANY other factors such as temperature, density of the gas, humidity, wind, state of your tires, etc. It would not be possible to measure it. Then you get into the issues of measuring equipment... 

    So it is always good to back up what in theory "should" be happening with measurements or the best audio test equipment ever devised, your ears. It is also important to understand the end user and the equipment they will be using. 

    Dave T