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ADAU1701 Sigmastudio Limiter questionings

Question asked by JulianoCioffi on Aug 15, 2015
Latest reply on Aug 27, 2015 by JulianoCioffi

Hello support,


Recently I checked several posts of the limiter and the main ones that I was looking for an information to help my customer were:

that has lead me to: Workaround: Creating constant-dB envelope decay using an existing linear decay algorithm

that finally has lead me to:


They are running SigmaStudio Ver 3.12.1 and I checked the release notes on 3.12.2 and no mentioning to limiter were made.


I am having some dificulties to understand how the Decay (Release) and Attack (RMSTC) work.


What are the units should I consider? In the Software RMSTC is considered db/s but it goes from 1 to 10000. Well I find that 10000 db is so much a huge value. Should I consider it then ms? 


I have found some indications to avoid overlaping that decay time constant should be greater than the attack time constant. But if they are measured by different constants, how can it be made? I saw this calculation:


Decay (in samples) = 4.4*10^6 / x

Where x = the setting in the control display.


Should it be fine or there is something new about this? Is there a formula also for RMSTC in samples time basis if it is really measured by db/s? My customer is looking for a Release time 16x greater than the Attack. Is there any graphics about the limiter provided for the ADAU1701 showing the cuttof frequency versus the recommended decay? For his case should I recomend that RMSTC has to be about 24 db higher than decay (16x faster attenuation)?


I Also tried to simulate the limiter in a basic block and was uncessfull. By pressing Stimulus 1_2 I only get the Probe1_2 response. Probe1 remains blank. I made changes in the filter parameters as well in the Eq and Volume control. I also tried the tone generator and it wont probe. How can I test the limiter?






Finally, where the bugs related to this corrected?




Best Regards,


Juliano K. Cioffi - FAE 

Latinrep South America - Analog Devices