ProtoDAC TDA1387 X8 project

[varunach]

You only need the one stacking header between the Q7 and ProtoDAC to prevent 5V from ProtoDAC feeding back to the 3.3V of the Q7 GPIO. Q7 isolates the topside isolated GPIO (J7) from the RPi. That is one of the things it does.

The noise is primarily conducted noise that the RPi is imparting on all of the GPIO lines, power, grounds and I2S, the entire GPIO. Q7 isolates J7 from all this. EMI is much less, orders of magnitude less, IMO.

Yes, I am saying that if you are going to circumvent the isolation of Q7, you might as well save yourself some money and go with MA. MA also has two jumpers so that you don't need to use the stacking header. See the previous posts of @michaelagiles . The solution in that case is to use an RPi that emits less noise. The RPi Zero W would have the least of the current RPi in that regard, since it is single core. In my experience, Zero W is less noisy than RPi 2, which is less noisy than RPi 3.

@hifinet I recently ordered one of your kits on EBAY and was intending to use it with the FiFoPi MA and a Raspberry Pi 3B+. Would you have any advice as to the optimum way to power that setup to reduce noise? I was thinking of powering the entire stack using the 5V J3 jumper on the MA and then shorting J4 1-2 3-4 (not exactly sure how to do that yet...).

But reading through the last few pages (and your post above) on this thread this will pass through RPi noise to the ProtoDAC correct?
If I'm wanting to use the MA, do you suggest I use a Zero W to minimise noise? I see from your signature that you use a Zero W. Do you find that WiFi interferes with/creates noise at all?

@wolf7250 yes thats what @hifinet is suggesting, to use ZeroW. Otherwise you'll have to have PurePi, lift the RPi3 a bit higher so that it doesnt use the ultracapacitors to power it (and use a separate 5V external power supply). On the shorting thing, you should get 3 small square black caps that you insert on top of the pins 1-2, 3-4 to short. Its shown in the FifiMa manual.