Difference between NxM mixer and signal add
Thread Summary
The user experienced clipping or distortion when using the Signal Add module to sum two identical sine waves, but not with the NxM mixer. The support engineer tested different summing methods in SigmaStudio 4.6 and found that the Signal Merger does not add gain, while mixers (including NxM) sum the signals with a 6dB gain. The user was advised to update to SigmaStudio 4.6 to avoid known bugs with the NxM mixer.AI Generated Content
Hi,
I find a question that when I use signal add module, two same inputs sine waves in, then the output from signal add is easily clip or distort. I know the output is out of my DAC's range which case the distortion.
However, when I use the NxM mixer module with the same inputs signals, the output will hard to distort. What's the diffrence between the two module?
I guess there is a function like the signal merger in NxM mixer. if I'm true, please tell me how to deal with signals in the NxM mixer.
Thanks!
Hello Foster,
Sorry for the delay. I am going back through old posts I missed.
You did not mention which DSP you are using. In addition it is helpful to know which revision of SigmaStudio you are using.
So I built a quick project to test the different ways to sum in SigmaStudio. Here is a screenshot of the project. It is written for an ADAU1452 but this should apply for all the SigmaDSPs.
So from top to bottom:
Addition
Signal Merger
Single Control Mixer
NxM with no slew
NxM with slew
In this screenshot you can see how the single control mixer and the NxM mixers are set to 0dB
The results is that all of the mixer outputs summed up the two correlated inputs to have the expected 6dB of gain. Only the Signal Merger's output was at the same level as the input, no gain.
In the past there have been some bugs that caused issues with the NxM mixers so that it why it would be good to know what revision and what processor you are using. There can also be other reasons for this.
I will attach the project I used if you want to experiment on your own.
Dave T
ADAU1452 Summing Comparison.zip
Hi,
Thanks for reply,I have tested signal add and NxM mixer is same.
By the way, I use sigmastudio 4.4, I want to know if this version fix the bug of NxM mixer?
Hello Foster,
I just looked at our internal bug reporting system and there were several issues that were fixed with the NxM mixers in SigmaStudio Rev 4.6. So update to the newest version would be advisable.
Dave T
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