P1FI DAC, I2S, random audio clicks ?(SOLVED READ)

[TommyBoy]

INFO for version 2.0 PIFI



REMOVE the DC/DC converter it is USELESS, all it do is add noise to your dc supply.
REMOVE the ferite called R8, ADD shortcircuit
ADD tiny resistor from DC/DC converter input to output footprint under the say FB2,
I used 1 ohm, but any value 1-5 ohms will be fine.
change C9 from 10uF to 220uF (voltage rating is not important 10-16-25-50V what ever)
I also added 220uF on the DC/DC module output pads (suck holes clean first) this way 5V in, is now super clean.
REMOVE C1 (you dont want to couple input dc ripple current into audio board ground)
REMOVE C20 (add bad MTBF and is useless)
DO this even if you hear no clicks or noise.

scroll back to page 2 for first version pifi mod pictures.

[g8chk]

Hi
I have this clicking issue with my RPI 3 and a p1f1 DAC+ v2.0.
So where exactly do I add the capacitor or capacitors, sorry for being a bit thick.

[TommyBoy]

this picture explain it more clearly ?.
AND, you need to do all of the stuff i explain in the previos post also.

[g8chk]

Sorry a couple of queries.
The text says remove c1 and c20, latest photo still has both in place?
A friend has offered to carry out the changes for me so at the moment I cannot see under the dc-dc converter.
What physical size should the resistor be, 0805?
Thanks Royston King

[TommyBoy]

you are right, Picture IS simply takes just before C20 was removed,
but the text is clear ! REMOVE it..
it is tantalium, low quality, and it will not help anywhere for good audio quality,
it will only give bad MTBF since such type of component often fail shorted.

the FB2 resistor, 1 ohm, 0805 size prefered, but 0603 size could also be fitted..

great you ask a friend with experiance in soldering, this way you get it right the first time.
also remember the other parts to change as listed a few posts back.

[ritsjie1971]

Very interesting!
I use the clone P1FI DAC+ v2 too, and will perform these modifications.

I was wondering, does this board need 5V too, or is it just used to create the 3V3 for the DAC? If not, perhaps it is wise to feed it via a 3V3 as described by lineair supply as described by fboe:
3x-powersupply-for-rpi-t4141.html?hilit=lt1963#p18118

I think it's better to do so instead of the onboard 3V3 regulator.

Since I'm planning on making a decent lineai supply this crossed my mind.

[TommyBoy]

there is ALWAYS a local linear dc regulator located near a DAC
else the dac will not perform as expected,
the dac run at 3.3V and the regulator needs a bit over this, for example 4-5 volts,
it is WISE to add a series resistor on the 5V in, and a local large cap, this way no ripple current flow from the PI
to the DAC board, I would NOT recommend to place a lin regulator, away from the DAC board,
or try to feed it with a nice clean 3.3 v from a remote location, unless you are VERY familiar with return path stuff.

the dac Draw very Little current about 37mA so a 1 ohm resistor give you 37mV drop
or a 10 ohm give you 370mV and ten times the filtering

[ritsjie1971]

OK!
I think a clean, seperate supply for the DAC will be better, but you're right about the return path trouble. I will figure something out when I have the time for it

[TommyBoy]

nothing will be better, no matter what kind of separate supply you can connect,
if noise is injected via ground path.

you can NOT split ground from DAC to/from PI since this ground is used for highspeed I2S signals.
(I2S stuff is super well isolated inside the dac chip, and will not go out the analog part)

BUT you can add a coil/resistor in series with the incomming DC, before a local DAC regulator,
this way data noise and supply noise do NOT mix.

using a DAC supply, located else where externally seen from the DAC, will only create new challange

[ritsjie1971]

I agree