1uF Capacitor for "internal bias decoupling":
If you can find the capacitor connected to pin 14 (Vcom - I think it's C411 but check with multimeter on continuity), this should be a 1uF Film type (Panasonic ECPU is normally used on better products), but on the Zen's is a ceramic capacitor. A small size Wima MKP with 2.5mm pin spacing fil cap, this should fit.
Looks like the Vcom is very important. It is for "internal bias decoupling".
Here is more info I found from the DSD1793 datasheet:
Info regarding "
internal bias decoupling":
Seems a good upgrade for the Zen DAC. Just wondering would that make any difference if I use a capacitor with higher uF? Is the WIMA one you mentioned the best replacement?
If I don't mind the component to be "flying over" (or the size of the component), would there be other better capacitor for the job?
Op-Amp U406:
The quad Op-Amp U406 could be replaced by OPA1644, this needs a proper SMD rework setup.
I kind of remember that iFi use a custom made Op-Amp for Zen DAC. Am I correct?
I tried to identify the Op-Amp labelled U406 but I cannot find any info about it. Is it a OPA1637 but a Quad version?
Is the Op-Amp U406 for the LPF as specified on the datasheet?
or it is for the Post-LPF?
Oscillator:
The clock oscillators are decent, but better options exists. No need to replace 12MHz, just 22.5792/24.576MHz. Again, needs SMD rework setup, so usually a tech at a smartphone shop is needed.
I think the 12MHz oscillators is for the XMOS (given it is labelled as X300).
I noticed that iFi use a very good labelling system for all the components on the PCB. It classified certain sub-system using their numbering system, i.e. 3xx is related to the XMOS system (as the XMOS chip is labelled as U
300)
Here are the prefix they use for the labels:
X: Crystal
U: CPU / Chip
R: Resistor
C: Capacitor
P: Plug
SW: Switch
J: Jumper(?)
L: ? <=== what is L?
For the 22M and 24M Hz crystals, what better replacement options you would recommend?
Copper foil:
Finally, "esotheric" measures, you can put self adhesive copper foil on the DSD1793 & Quad Op-Amp Chips and connect it to ground. Ideally the XMOS Chip too but that's a bit dicey to work on.
Do you think aluminium foil would be ok too? It is easily available in kitchen.
I have a stupid idea
. I am thinking wrapping aluminum foil (grounded) by food plastic wrap (for insulation). Then use it to cover the chips you mentioned about. Does it make sense to you? Or it is just something stupid and does not work? LOL.
Cheers