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PCB I2S connector

Piotr Czepek

February 21, 2014 16:29

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Hello,

What is for second I2S connector on the top side of the DAC board?

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12 comments

• 0
  
  HiFiBerry team February 21, 2014 16:54

  Hi Piotr,
  
  it can be used to use the board as a standalone DAC for circuits that create I2S signals. It can also be used for debugging. There is no circuits that can simply plugged onto this connector.
  
  Best regards
  Daniel
• 0
  
  Piotr Czepek February 21, 2014 17:51

  Thanks Daniel for explanation.
  Can I have (theoretically) second DAC connected to the I2S connector for quick sound comparison? Of course I have rmmod/insmod module driver to switch them.
  
  I have TDA1543 NOS-DAC, I would like to test both DAC's without plugging/unplugging.
  
  One more question - do you think we can get lower distortion if we use hifiberry DAC as a standalone DAC? No direct piggyback connection on RPi, but with i2S cable.
  
  
• 0
  
  HiFiBerry team February 23, 2014 08:59

  Hi Piotr,
  
  I do not expect distortions to be lower with an I2S cable between the boards. It can be even get worse, as the signals on the I2S cables will be several MHz, with 192kHz sample rate even >10MHz. This might create RF problems. Therefore I do not recommend this.
  Having another DAC in parallel, that does not need any configuration and just works as an I2S slave might work. However, I2S is not designed for things like this. Therefore there might be problems. If you want to compare different versions, I recommend using different Raspberry Pis.
  
  Best regards
  Daniel
• 0
  
  Piotr Czepek March 13, 2014 09:05

  Hello Daniel,
  
  I received my order. HiFiBerry works really great for me ;-)
  I'm trying to put RaspberryPi in nice aluminium case, and there is small problem for me.
  I don't want to use the stacking header. Unfortunately the set of RPi+HiFiBerry+stacking header is too high to fit in my case.
  
  So I decided to mount HiFiBerry aside RPi.
  And there is my question. How to make "perfect" I2S cable for HiFiBerry?
  Distance I need is about 10cm.
  Can I use flat ribbon cable? Do I have to separate each "live" strand with ground strand?
  Use coaxial cable? Isn't overkill?
  
  Regards
  Piotr
• 0
  
  HiFiBerry team March 13, 2014 14:14

  Try a short ribbon cable. Keep it as short as possible. With an aluminium case, the risk of RF emissions to the outside is relatively low.
  We haven't done any measurements of this setup, therefore we recommend just trying this.
  
  Best regards
  Daniel
• 0
  
  Piotr Czepek March 13, 2014 14:59

  Ok, thanks.
  I will try with ribbon cable.
  What pins can I skip for connection?
  Of course PCM_IN - is not used, but I'm not sure for 5V - is it used?
  
  Now I use single jumper wires for each pins. It works, but it doesn't look like good engineering ;-)
  
  In fact I'm not afraid of RF emission out of the case.
  I'm afraid of so called "Line induced jitter" and "Interfering-noise induced jitter" as stated here: http://www.tnt-audio.com/clinica/jitter1_e.html
  
  Best regards
  Piotr
• 0
  
  luuk February 09, 2015 19:42

  hi Piotr, which aluminium case do you use for the RPi?
  I'm looking for a cheap aluminium case which I can easily modify to allow the connectors of the Digi+ to be embedded, so it would be a shame to order a case which is too low!
• 0
  
  Piotr Czepek February 10, 2015 18:05

  Hi,
  There is few photos of my setup:
  https://picasaweb.google.com/116430780505722402631/RaspberryPiES9023I2SDAC
  
  There is enough room for RPi, wifi module, DAC, 5V/7A power supply and 2.5' HDD.
  Not a cheapest, not a smallest, but quality is very good.
  
  
• 0
  
  luuk February 11, 2015 13:59

  Wow looks amazing Piotr! Where did you buy the aluminum case?
• 0
  
  Piotr Czepek February 11, 2015 14:32

  Here you are, this is my shoping list:
  
  A nice alu case:
  http://www.ebay.com/itm/Full-aluminum-Case-Box-for-weiliang-PGA2310-PGA2311-CS3310-Preamp-/130785455085?hash=item1e736babed
  
  Aluminium chassis feet:
  http://www.ebay.com/itm/4PCS-30-14mm-Silver-Aluminum-CD-Player-Speaker-DAC-PC-Chassis-Amplifier-Feet-Pad-/321121727938?pt=LH_DefaultDomain_0&
  
  Power supply:
  http://www.ebay.com/itm/AC110-AC220V-to-DC5V-7A-35W-Universal-Regulated-Switching-Power-Supply-/111018535151
  
  OLED display - looks faar better than generic LCD, but needs small hacking in software (LCDd):
  http://www.ebay.com/itm/IIC-I2C-1602-16x2-OLED-Module-Display-For-Arduino-PIC-AVR-ARM-/161162845021?pt=LH_DefaultDomain_0&
  
  HDMI output:
  http://www.ebay.com/itm/Screw-panel-mount-hdmi-male-to-hdmi-female-extension-cable-/351308822428?pt=LH_DefaultDomain_0
• 0
  
  luuk February 15, 2015 15:23

  Thanks for the extensive response Piotr!
  Did you already find a solution for the extension of the I2S connection?
• 0
  
  Piotr Czepek February 15, 2015 16:02

  Now I have just jumpers as I2S connection between the DAC and the RPi. It is about 10cm long, but it makes a lot of EMI when audio device is open.
  
  I bought some of a coaxial cable:
  http://allegro.pl/przewod-teflonowy-50ohm-1-76mm-do-urz-lampowych-i5091776062.html
  any other wifi cables should be fine.
  I would like to put each I2S line in separate cable. I know, this is not perfect design, there should be a 50ohm driver for GPIO.
  But for short distance it will be better solution than a generic unshielded wire. I hope ;-)