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DAC+ DSP: Build a stand-alone DAC

Pierre Piotrowski

October 18, 2018 12:14

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Hi,

 

I want to built a stand-alone DAC using the DAC+ DSP board. I got a Behringer ECM-800 to measure the room response to use the DSP. The DAC shall be used at my work PC to change the outcoming toslink signal into a analogue signal which then continues to the amp.

Concerning this project I got a few questions:

-Can I operate the DAC DSP board without an Raspberry Pi it is attached on? Is it possible to attach a toslink output from the pc to out and to get the analogue DSP signal out by just supplying power to it?

-How to attach a power supply to the board?

-Will the board then be switched on, when the power supply is on, otherwise it is simply off?

-Can I attach it once to a Raspberry Pi, write the dsp .txt. file coming out from REW and then it will use these filter settings without the Raspberry?

-Would it be possible to create a multichannel solution? For example to run a small sourrung system to use two of these boards for the output? How to get multichannel over toslink divided to the different boards for front and rear?

 

So far these are the most pressing ones

Thank you very much

Pierre

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30 comments

• 0
  
  HiFiBerry team October 18, 2018 12:54

  Hi,

  while you can operate the DAC+ DSP, each change on the parameters need a Raspberry Pi. So the recommendation is to always use it with the Raspberry Pi.  It will start when power is connected. 
  If you want to use it without a Raspberry Pi, you need to connect power via the GPIO header.

  TOSLink is not a multichannel interface, it just supports 2 channels. So you can't use more than 2 channels on a single TOSLink.

  For the measurement microphone, you will need a separate microphone preamlifier and a sound card with an input. It might be easier to get a USB measurement microphone.

  Best regards,
  Daniel

   

• 0
  
  Pierre Piotrowski October 18, 2018 13:06

  Thanks for your answer:

  I got a USB interface for the mic. So I am operational on that part.

   

  What I still dont get:

  When I plug the toslink from the pc into the DAC+ DSP and put some energy to it, i will get the analogue output, which I can then pass to the amp?

   

  Is it possible to run the DAC+ DSP with a Raspberry Zero?

   

  How is the miniDSP (https://www.oaudio.de/MiniDSP/miniDSP-2x4-HD-Boxed.html) working with 4 channels, when attached to a toslink? I guess it works only with multichannel when used via USB?

   

  Best regards

• 0
  
  HiFiBerry team October 18, 2018 13:10

  Yes, you will get analogue output from the SPDIF input.

  Yes, you can use a Raspberry Pi Zero. However, I would always recommend the "bigger" 3B+. With the Zero-W you only have WiFi connectivity. If this breaks for some reason, it is hard to fix and debug. With Ethernet on the 3B+, it's much easier - no credentials needed, just plug it in and it will usually work (with DHCP).

  I can't comment on any competitors products, but I would guess that the MiniDSP does only support 2 channels from USB.

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 10:55

  Ok, so I got most I need. One more:

   

  Is there any way to integrate a volume control? Dac DSP attached to the PI integrated with a PSU into a case and then a volume poti would be ideal. How to realize that?

   

  Best regards

• 0
  
  HiFiBerry team October 19, 2018 10:57

  With HiFiBerryOS on the Raspberry Pi, you can connect a rotary control for volume control. This is still experimental, so it might still need some bugfixing.
  You can also use other software on the Raspberry Pi to control the volume with a rotary control or an RF remote control.

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 11:02

  So I would need to use an OS which allows to write the filter.txt to the DSP board and which can be connected with the volume control? Any alternative to the HifiBerryOS?

   

  I did not find any rotary control knobs in your shop. What kind of rotary control do I need? How is it connected to the PI?

• 0
  
  Pierre Piotrowski October 19, 2018 11:08

  https://www.amazon.de/kwmobile-Rotary-Encoder-Raspberry-Arduino/dp/B06XHHSVN1/ref=sr_1_3?ie=UTF8&qid=1539947196&sr=8-3&keywords=KY040

   

  I found this one.

  How can it be used with the DSP board on the same time on the PI?

• 0
  
  HiFiBerry team October 19, 2018 11:25

  This rotary control encoder should work. 
  For connections have a look at the audiocontrol documentation: https://github.com/hifiberry/audiocontrol/blob/master/doc/rotary.md
  
  Audiocontrol is a piece of software that's included in HiFiBerryOS. 
  
  You can use whatever software you like with the Beocreate board. You're not limited to HiFiBerryOS. However, you might need to install additional software (at least the DSP software). If you just want to control the DSP with it, I think, HiFiBerryOS is easiest to use as you don't need to install additional software.

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 11:38

  Hi,

   

  I don't plan to use the beocreate board but the DAC+ DSP in conjunction with a PI.

  The connections I saw already, but what I don't understand is, how I can connect the rotary control to the PI when the DAC+ DSP is connected as well, as the GPIO pins are used?

   

  Best regards

• 0
  
  HiFiBerry team October 19, 2018 11:39

  On the DAC+ DSP you would have to solder cables directly to the board.

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 11:57

  From the git hub audiocontrol docu:

  "V+ will be connected to a 3.3V pin of teh Raspberry Pi (NEVER to 5V!) and GND to a ground pin.The CLK, DATA and SWITCH pins need to be connected to an unused GPIO of te Raspberry Pi. You can configure these."

   

  But are there unused GPIO on the PI left, when I put the DAC+ DSP on it?

• 0
  
  HiFiBerry team October 19, 2018 11:58

  Yes, there are unused GPIOs. We'll document the GPIOs uses by the DAC+ DSP soon.

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 12:04

  Ah ok, now I get it. So I would need to put the 5 pins of the rotary controler between the connectors of the DAC+ DSP and the PI to the correct unused pins.

  So I look forward to the documentation of the DAC+ DSP pins, so I can begin with the project.

   

  Thank you for your time and answers!

• 0
  
  HiFiBerry team October 19, 2018 12:07

  You can't really connect these "between", but you have to solder the cable to the DSP board. You can use the GPIOs in the audiocontrol documentation linked above, these are also unused on the DAC+ DSP.
  
  

  Note that GPIOs are not Pin number, so check the mapping of the GPIOs to pins here:
  https://docs.microsoft.com/en-us/windows/iot-core/learn-about-hardware/pinmappings/pinmappingsrpi

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski October 19, 2018 12:13

  Ok.

  Are the pins on the DAC+ DSP also connected to a black plug which gets inserted to the Raspberry PI?

  When I solder the rotary control cables to the DSP board, do I solder them to the rear side of the black plug, on the smal back sides of the pins?

• 0
  
  HiFiBerry team October 19, 2018 14:23

  You would need to solder them where the GPIOs are soldered onto the board. Note that you should not do this if you're not experienced with this as you might damage the board and you will void the warranty with this.

  Best regards,
  Daniel

• 0
  
  Dietmar Wolf October 21, 2018 10:41

  Hi,

  I am not shure if I understood the above right: Do I really need the GPIO-pins to attach an external power supply? Do I really have to solder something on the board to use this advertised feature "standalone dac", seriously?

  Why did you remove the feature to use on-board pins (P3) for an external supply, which was persent on the other boards?

  regards

  Dietmar

• 0
  
  HiFiBerry team October 22, 2018 05:52

  Yes, you understood this correctly. We did not remove something, the DAC+ DSP is completely different than other boards. It is way more complex and adding an additional power connector just wasn't easy to do. If you run the board stand-alone, you can also use a 4'-pin male header and connect the power using this one.

  Best regards,
  Daniel

• 0
  
  Dietmar Wolf October 23, 2018 10:20

  Thank you Daniel,

  at least one doesn't have to remove an smd resistor any more... ;)

  I am looking forward to finding a hardware guide for the new board.

  Best regards

  Dietmar

• 0
  
  Pierre Piotrowski November 17, 2018 11:05

  Hi,

   

  I am actually searching for the HifiberryOS you mentioned. I got a bit trouble finding git, can you please give me a hint?

   

  Beste regards

  Pierre

• 0
  
  HiFiBerry team November 17, 2018 11:09

  Hi,

  the images are on Github:

  https://github.com/hifiberry/hifiberry-os/tree/master/images

  Best regards,
  Daniel

• 0
  
  Pierre Piotrowski November 17, 2018 11:10

  Thanks!

• 0
  
  Pierre Piotrowski November 19, 2018 19:07

  Hi,

   

  I am using the Pi Zero and tried the HifiberryOS from the Github you mentioned. I just get the Colorscreen, but nothing more happens during the boot. I tried Raspbian and Volumio as well, they both work. 

  Is the Pi Zero not supported by HifiberryOS?

   

  With Volumio I got the problem that the driver for the DAC+ board ist not working with the DAC+ DSP.

   

  Any suggestions what chance I got to get it running? Is the Hifiberry driver available for Volumio?

   

  Best regards 

  Pierre

• 0
  
  HiFiBerry team November 19, 2018 19:12

  Hi,

  HiFiBerrOS does not support the Raspberry Pi Zero.

  With other distributiosn, you need to use the hifiberry-dac overlay.

  Best regards,
  Daniel

• 0
  
  Dietmar Wolf December 16, 2018 11:24

  Hello again...

  in the meantime I was able to find the dac+ dsp datasheet: https://www.hifiberry.com/build/documentation/datasheet-dac-dsp/
  and identified the raspberry's gpio layout with the link in the above thread:
  https://docs.microsoft.com/en-us/windows/iot-core/learn-about-hardware/pinmappings/pinmappingsrpi

  What still is not clear to me, if I want to implement a separated power supply for hifiberry and raspberry:
  - Which pins on the hifiberry-board should be connected to the power supply (having 5V)?
  - Which pins on the hifiberry-board should then be disconnected from the raspberry?
  - Do I need an extra +3,3V for the hifiberry?

  Best regards
  Dietmar

• 0
  
  HiFiBerry team December 16, 2018 11:27

  Hi,

  is is not supported to power the DAC+ DSP and the Raspberry Pi seperately. This would require cutting traces on the PCB. This could damage the board and will void warranty.

   

  Best regards,
  Daniel

• 0
  
  Dietmar Wolf December 16, 2018 14:15

  Ah, now I've got it! I completely misunderstood the "standalone" thing ;)
  I have to re-think my projects...

  Thanks anyway!

  Happy Christmas

• 0
  
  HiFiBerry team December 16, 2018 14:15

  What exactly do you plan to do?

  Best regards,
  Daniel

• 0
  
  Dietmar Wolf December 16, 2018 14:35

  Well - if you want to know the whole story:
  (1) I wanted to build the "ultimate" streaming client (for spotify mainly)
  (2) I wanted to use dsp for a digital improvement of my old spherical loudspeakers.
  (3) I also appreciated the opportunity to use the dac for other sources (e.g. tv) when raspberry is off.

  Now I read an article a while ago from someone who had two separate power supplies - one for the raspi and one for the "analog part" of the hifiberry PCB - with de-soldered r14 and all that stuff. He also separated the two boards by using some 40-line flat cable.

  I wanted to do the same and ordered a respective analog psu from thel (havin 2* 5V) and 3A.

  I just wanted to put some effort into the improvement of power (for nerd reasons).

  Only the dac+ dsp would not do me the favour...

  Or?

   

• 0
  
  HiFiBerry team December 17, 2018 19:07

  Yes, the DAC+ won't do you the favour. However, the DAC part itself is powered by a separate linear power regulator on the board. Therefore we don't think, a separate power supply is needed.

  Best regards,
  Daniel