external PSU and LatchUp-Effect


as many posts here as well as elsewhere on the internet suggested, the quality of the DAC+ Pro can be improved by using a separated PSU. So I'm planning to do this right now.

As my assumptions are only based on looking at pictures of the board (the newer one of course) there is maybe a mistake in the facts my assumptions are based on. Therefore I will enlist those "facts" first:

1.) By default the board seems to use both voltages provided by the RPI.

2.) 5V is only used to generate the 3.3 V used for analog parts of the DAC. The chip on the board used to generate those 3.3 V analog seems to be U2.

3.) 3.3V coming from the RPI is then used to power the digital parts of the DAC as well as the clocks.

If any of the facts above are wrong please correct me.


Now to my questions:


a) If I would use a separate PSUs to power the 5V part (or 3.3 V analog directly instead), is there a risk of a LatchUp-Effect (or something similar) if the separate voltage is powered up/down sooner/later than the digital 3.3 V coming from the RPI.

b) If I would also connect another 3.3 V PSU to the digital 3.3 V line (while of course disconnecting the line coming from RPI) could this cause a LatchUp-Effect if not powered up/down in a defined order?

c) I read something about 100 mA analog load (maximum rating) in another thread concerning a separate PSU. Does anyone know whats the digital 3.3 V load of the whole board (maximum rating).

d) Would it even make a noticeable/measureable quality change to switch out the digital 3.3 V with a more linear separate PSU (assuming the 3.3 V analog is already on very high quality).


Thank you in advance for your answers! If I find out anything myself I will post it here of course.


Please sign in to leave a comment.