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Access to BQ-filter in TAS5713

Karl-Heinz Fink

August 01, 2016 11:21

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Hi Daniel,

 

the class-D chip has a few BiQuad filters per channel that can be used to EQ speakers. Is there a way to access them and set parameters? It would be easy to make corrections on speakers........I'm happy to  define parameters for a few popular speakers, so they can be used together with the Amp. This could also include corrections for positions in the room (on the wall, free standing). Would be really fun and gives the amp some extra use. I'm in Horgen from time to time, so maybe we can meet on my next trip to Zürich See :-)

Best regards

Karl-Heinz Fink

 

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7 comments

• 0
  
  HiFiBerry team August 01, 2016 13:30

  Hi Karl-Heinz,

  unfortunately this isn't supported. This would need major work on the driver. It would also need a different set of filters for different sample rates. We're not working on this.

  Best regards,
  Daniel

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  Karl-Heinz Fink August 01, 2016 14:45

  Hi Daniel,

  pity, that could have been a good commercial solution as well. I don't know enough about the hardware (only speaker engineer), so I need to find somebody who might do it for me.

  However, thanks for the information :-)

   

  Best regards

   

  KH

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  Stefan S. August 22, 2019 16:20

  Hi Karl-Heinz,

  Well, your post is a little bit old but ...

  Yesterday, I was not so happy about the alsa software equalizer and remembered that the TAS5713 has the capabilites to do some equalizer tasks. So I started to dig a little bit deeper. After many hours reading in TI's forum, many lines of source code and get some knowledge about the used biquad structure of second order IIR filters I was able to configure the AMP+.
  
  Well it's more a hack than an clean linux driver implementation but it works. In the end you can access the I2C interface and override the registers of the TAS5713 IC on the fly by userspace code ... or automatically after boot by systemd.

  If you are interessted, I can share the scripts which do the magic. The filter designer is text based (Python) but there is also a graphical frequency response view of your creation. Just let me know...

• 0
  
  HiFiBerry team August 23, 2019 06:39

  Hi Stefan,
  
  it would be interesting to see this. Sounds a bit like it won't have a chance to make it into an official kernel. But the good thing about open source is that you can still do it ;-)
  BTW: If somebody wants to experiment: We still have a few refurbished Amp+ units left:
  https://www.hifiberry.com/shop/boards/hifiberry-amp-plus/
  
  Best regards,
  Daniel

• 0
  
  Stefan S. August 23, 2019 14:05

  Hi Daniel,

  That stuff will never reach the kernel. However, as you write, I had my moments when I found the driver implementation of the TAS5713. The file tas5713.h contains the init sequence where the biquad coefficients are set to default values. So just modify and compile ... (well, which kernel revision do I use at the moment ?) ... and my problems with that solution started...

  However. My python script works good enough for me and it is a little bit more flexible. I made a git repo (https://github.com/kungpfui/tas5713-biquad) with my scripts. Just enjoy!

  Please note: I'm not absolutly sure everthing works as caculated. For me it sounds like every filter setting does what I want. A real verification with sine sweeps and measurment equipment is still pending.

  LG Stefan

   

   

• 0
  
  HiFiBerry team August 23, 2019 15:36

  Can you access the I2C device with the driver loaded? This shouldn't be possible.

  Best regards,
  Daniel

• 0
  
  Stefan S. August 23, 2019 15:46

  Yes, I can ... or smbus2 can.

  The trick is to use forced i2c slave access.

  # Commands from uapi/linux/i2c-dev.h
  I2C_SLAVE_FORCE = 0x0706 # Use this slave address, even if it is already in use by a driver!

  I expected also some more troubles after my forced access. Like no more working volume control but that was not the case.
  Stefan