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HiFiBerry DAC+ ADC Pro: Can I directly drive into FOH mixer

Christof

February 22, 2023 13:50

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I want to use HiFiBerryDAC+ ADC Pro as an effect box on stage.

* Can the output used directly to drive a symmetric input of a FOH mixer? 

* How should the outputs be wired to XLR connectors to have the optimal sound quality?

* Or would it be better to use an additional Stereo DI Box between the output and the Front of House mixer.

* Could there be peaks and loud noises during the startup of the RPI

* If so, how can it be avoided.

* Is there a simple way to bypass the processing (in case there are some software issues (never trust our own engineering). So that whatever signal is in the input is passed to the output?

 

Thank you very much for your opinions

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11 comments

• 0
  
  HiFiBerry team February 24, 2023 05:31

  Output on the DAC+ ADC Pro is unbalanced. There is no symmetric output. Usually you can connect an unbalanced output to a balanced input without problems. Just pull the cold input to GND.
  
  Peaks and noises are always possible depending on your setup. You need to check your specific setup.
  
  There is no input/output connection. Audio always have to be handled via software on the Pi. If you just want to copy the data without modifications, have a look at "alsoloop".

• 0
  
  Christof March 04, 2023 13:50

  How does the output stage on the DAC+ ADC look? I could not find any information about it.

  Is there anything that should added to make the output signal good for stage usage. Is there any electrical protection needed? 

  How can ground loops be avoided?  It would be great to get some information about the circuit that is behind the DAC output to learn more about what would make sense to add between the DAC and the Mixer input.

   

• 0
  
  HiFiBerry team March 06, 2023 08:03

  It's a normal line driver. If you just connect it to an mixer input , there is nothing special about it. If your mixer/pre-amplifier is just normal no protection is needed. Make sure you don't send 48V phantom voltage to the DAC because this will definitely damage it.
  
  Ground loops are a different thing. There is nothing special with this on the DAC+ ADC. There is no simple rule how to avoid ground loops. Best is to make sure devices share the same ground. 

  Edited by HiFiBerry team March 06, 2023 08:32
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  Christof March 08, 2023 13:16

  Is it an additional line driver or the direct output of the DAC that is connected to the Output Connector P5?

  If 48V might damage the output, I think then its worth to add some sort of protection. It's not easy to ensure that all Sound Engineers will always keep their hands from that button on their mixer. 

  I can of course use an extern DI to avoid that. However I would still be interested on a simple protection circuit.

  Maybe somebody has some experience with this sort of question?

• 0
  
  HiFiBerry team March 08, 2023 13:20

  The DAC has an integrated line-driver. Output of the RCA jacks and the additional pin header is exactly the same. 
  A bidirectional Z-Diode of about 4V should provide anough protection for the DAC (it hasn't been tested, therefore I can't guarantee this). 

• 0
  
  florit March 19, 2023 10:37

  * How should the outputs be wired to XLR connectors to have the optimal sound quality?

  One wire on port1(XLR Jack) means ground

  One wire on port2(XLR Jack) means minus

  Two wires on port3(XLR Jack) means plus

  this on the other side of the cable too!

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  Christof March 20, 2023 06:57

  Thank you very much for your suggestions and help.

  I am still thinking about adding a proper differential line driver to the output. For example https://thatcorp.com/datashts/THAT_1606-1646_Datasheet.pdf

  What do you think about this idea?

  Would this be an improvement? (Probably the THD would suffer)

  Can the +5V output on P5 of the HiFiBerry be used to power such a stage, (or is this an input)?

  Best Regards

• 0
  
  HiFiBerry team March 20, 2023 07:41

  This would require some serious hardware development. It's not just "connecting a driver". The 5V from the Pi would definitely need filtering. I wouldn't recommend this if you're not an very experienced developer of analog circuits.

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  Christof March 20, 2023 13:22

  Sure I fully understand that developing an output stage is not an easy task!

  Even if possible, its probably not worth the effort, since there are many such devices available (https://en.wikipedia.org/wiki/DI_unit). And its definitely easier to use such an existing device. It solves both, the problem with the Phantom Power that is often exposed on professional mixer inputs, and also the conversion to symmetrical lines in order to support longer cables to the mixing console. 

  However I would still be interested in the quality of the 5V that is (according to the Data Sheet) is on Pin 1 and 5 of the P5.

  From your answer it sounds like its just the 5V of the Pi. Is it the same as on Pin 2,4 of the Pi 40 Pin Header? How much current can you draw from P5 Pin 1/5?

  I guess you don't want to share some more information how you solved this very problem on the https://www.hifiberry.com/shop/boards/hifiberry-dac2-pro-xlr/ ?

• 0
  
  HiFiBerry team March 20, 2023 16:20

  The DAC2 Pro XLR uses a different DAC with balanced outputs.

• 0
  
  Christof March 21, 2023 17:03

  Many thanks for the answer, makes sense then to me. Would be very cool to have a similar version also for the DAC/ADC+ (Pro * Pro). I like really like the HiFi Berry products.