powering pi-dac from IQaudio

Audio Gear DACs
1

Hello,

I would like to separate the power from the pi and the pi-dac from IQaudio (iqaudio.com/?page_id=28) using linear power supply rails (5 and/or 3.3v).

I did exchange some emails with gordon and read the product doc file : iqaudio.com/wp-content/uploads/2 … IO_Doc.pdf :

  1. Extreme hacking (Raspberry Pi Pins)
    For those who want to do things like Power the Pi DAC from a separate power source than the Raspberry Pi itself the following may be of help although we do not recommend using the Pi DAC in this way.

The following Pi Pins need to be connected to the corresponding PiDAC headers for audio to work. We recommend that the other Raspberry Pi ground pins are also connected.

P1 (26way): 3 (I2C SDA)
5 (I2S SCL)
17 (3.3v)

P5 (8 way): 1 (5v)
2 (3.3v)
4 (I2S LRCK)
6 (I2S DATA)
8 (GND)

  • I did not understood why there is two “3.3v sources”. any suggestions ?
  • Did I have to “merge” the grounds from the 5V and 3.3V ?
  • Considering (this is a personal assumption) that the 3.3v is for the digital treatment and the 5V is for the anagogic treatment, would it make sense to use the 3.3V from the pi and the 5V from a linear psu ?

thanks for your help

Francis

2
  • I did not understood why there is two “3.3v sources”. any suggestions ?

Top Secret :slight_smile: The two are needed just connect them

  • Did I have to “merge” the grounds from the 5V and 3.3V ?

there is only one ground.

  • Considering (this is a personal assumption) that the 3.3v is for the digital treatment and the 5V is for the anagogic treatment, would it make sense to use the 3.3V from the pi and the 5V from a linear psu ?

yes 3v3 for digital and 5v for analog circuitry
I’d try to keep the power to the DAC just that - power to the DAC (both 3v3 and 5v).
I know what you are trying to achieve but we put a lot of effort into getting the quality o the voltage right on the Pi-DAC, you may not receive the benefit you think is achievable but hey ho - give it a go and please report back your findings.

How are you planning on measuring the improvement - by ear?

Best,

Gordon@iqaudio.com

3

Hi gordon,
What do you think about the following wiring scheme ? (see picture below). My goal is to NOT place your dac on the top of the pi (to be able to keep all the stuff connected to my gpio port). I could connect your dac to the pi using cables.

Then, if this is not secret :slight_smile: why your dac need the pin 3 (I2C SDA) and pin 5 (I2S SCL) from the raspberry pi gpio to work ?

power-iqaudio.jpg

4

Did you ever resolve this. I am facing a similar problem on a different piece of hardware. My board needs 5V and 3.3V and only has one ground. The 5V stuff seems to work when I plug in just 5 volts and ground .The 3.3V stuff works when I plug 3.3V and ground. But If I plug in both, and connect the power supply grounds, nothing works.