[Thorsten Loesch]

As my super charging solution is based on 5.5V capacitor, would it be ok to use it with 5.7v input?

No, you better stick to 5.25V, 5.5V absolute max.

BTW, for the 5.7V you mentioned, does it refer to the voltage under load (i.e. connected to the Zen DAC) or w/o load?

Normal load.

Thor

 

[sunjam]

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 U300)

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

 

[Thorsten Loesch]

Info regarding "internal bias decoupling":

I entertain considerable doubts about most of this "information". It (as usual) illustrates why "AI" can barely replace advertising copywriters and even then is entirely derivative.

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?

Panasonic SMD Film is better, but is is not possible to fit it. You can try larger values, os-con, silmic, they all sound subtly different.

If I don't mind the component to be "flying over" (or the size of the component),

The WIMA cap will do that. You might want to glue it on top of the IC.

U406:

I kind of remember that iFi use a custom made Op-Amp for Zen DAC. Am I correct?

The customisation was the label. Many parts in ifi gear are customized. Perks when buying a lot and being able to wait a few months.

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?

Under the bonnet is OPA1679. It's an underrated part, it's actually the same die (the "chip" inside the IC) as OPA1654 which is 95% of an OPA1656.

It much cheaper than than "master" part because it gets tested a lot less and some parameters that are guaranteed on OPA1654 are not guaranteed or more relaxed tolerance on the OPA1679.

But this has no impact on sound quality. It is surprisingly good all-round and can take on a lot of the best single purpose options from the 80's and 90's.

All that said, OPA1644 sounds a little different and at least to my ears a little better, more relaxed and natural.

Is the Op-Amp U406 for the LPF as specified on the datasheet?

No, the circuit naturally is not the datasheet one. It has some important tweaks.

Oscillator:

I think the 12MHz oscillators is for the XMOS (given it is labelled as X300).

Correct.

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 U300)

That is my system of labelling.

J: Jumper(?)

Correct.

L: ? <=== what is L?

Inductor.

For the 22M and 24M Hz crystals, what better replacement options you would recommend?

No recommendation, sorry. Crystal seems to have good reputation.

Copper foil:

Do you think aluminium foil would be ok too? It is easily available in kitchen.

No, it's not possible to solder, lacks adhesive backing.

I have a stupid idea .

It is not a good idea.

Thor

 

[stuck limo]

I'm currently using the iFi iPower X 5v/3A on my Zen One Signature DAC. How much further can I realistically go/get if I upgrade? And nothing over 5A or 5.5A should be used if I'm understanding this correctly? Correct me if I'm wrong.

 

[Thorsten Loesch]

I'm currently using the iFi iPower X 5v/3A on my Zen One Signature DAC. How much further can I realistically go/get if I upgrade? And nothing over 5A or 5.5A should be used if I'm understanding this correctly? Correct me if I'm wrong.

The Zen DAC is fine with 5V/1A. More current as such will not do a lot.

Thor

 

[stuck limo]

The Zen DAC is fine with 5V/1A. More current as such will not do a lot.

Thor

Great I'll leave it alone. I did notice a boost and minor improvement when I switched from the stock to the X.

It's my understanding there's no galvanic isolation in the Zen One, correct? I'm currently using the micro iUSB 3.0 and the iGalvanic on it.

 

[Thorsten Loesch]

I have a stupid idea .

Please see these two links on the What, How, Why, Whodunnit etc.:

https://emcesd.com/tt2011/tt050411.htm

https://www.researchgate.net/public...e_Source_Chip_for_a_Johnson_Noise_Thermometer

I hope in the process of digesting these it will become crystal clear why Alu foil and Cling Film are a terrible idea.

Thor

 

[Thorsten Loesch]

It's my understanding there's no galvanic isolation in the Zen One, correct?

I know nothing of what iFi did in the Zen ONE, sorry except that most of it appears copied verbatim from the iOne nano, including the rather crippled analogue stage with MAX97220 - except they made the output balanced by inverting the normal output. I quite cringe whenever I see this. They have a far superior design they just needed to Copy/Pasta from the Zen DAC and they did not.

Galvanic isolation is unlikely.

I also suspect that also the automatic disconnection of Vbus and USB Ground that the ZEN DAC does when running on external power has not been integrated. But you really ned to ask iFi about that.

Thor

 

[Thorsten Loesch]

1uF Capacitor for "internal bias decoupling":

Here a closeup of the DAC section from the iDSD Pro. It shows the capacitors used around the DAC Chip in this:

From the colour you can see that small ceramic capacitors around the DAC Chip are 0.1uF/25V/0603 C0G/NP0 Ceramic types, these are nearly as good as PTFE Capacitors. The analogue supply pin's and Vcom additionally have a 1uF Panasonic ECPU capacitor. There are more capacitors below the PCB and ultimately 330uF/6.3V Os-Con's for L/R DAC 3.3V logic and Elna Silmics in the 5V analogue supplies.

On the left you can also see the two supercapacitors (C210/226) that handle the filtering of the supply for clocks, DAC etc.

U207/208/210 are reclocking, the clock itself is hidden and placed above U207.

Thor

 

[sunjam]

Here a closeup of the DAC section from the iDSD Pro. It shows the capacitors used around the DAC Chip in this:



From the colour you can see that small ceramic capacitors around the DAC Chip are 0.1uF/25V/0603 C0G/NP0 Ceramic types, these are nearly as good as PTFE Capacitors. The analogue supply pin's and Vcom additionally have a 1uF Panasonic ECPU capacitor. There are more capacitors below the PCB and ultimately 330uF/6.3V Os-Con's for L/R DAC 3.3V logic and Elna Silmics in the 5V analogue supplies.

On the left you can also see the two supercapacitors (C210/226) that handle the filtering of the supply for clocks, DAC etc.

U207/208/210 are reclocking, the clock itself is hidden and placed above U207.

Thor

Thanks for your photo and detailed info. It gives me a good insight about what else can be further improved for the DSD1793.

From the following photo of the circuit,

Looks like that (I need to further confirm with a multi-meter)

C411: between Vcom (pin 14) and GND
C412: between VccL/VccF (pin 20, 21) and GND
C413: between VccR (pin 10) and GND
C414: between VccC (pin 15) and GND

I have a few 470uF OS-CON (6 pcs) and Elna Silmic capacitors (2 pcs) left over.
I was wondering if I can solder them on top of the existing ceramic capacitor (i.e. in parallel config)?

To be exact, my plan is to

add one 470uF OS-CON to each C411,C412,C413 and
add one 470uF Elna Silmic to C414

Or is it better to replace the existing ceramic capacitors?

Does it make sense to you by adding (or replacing with) the OS-CON / Elna capacitors as stated above?

BTW, "On the left you can also see the two supercapacitors (C210/226) that handle the filtering of the supply for clocks, DAC etc" <=== what are the capacitance of these supercapacitors?

 

[Thorsten Loesch]

C411: between Vcom (pin 14) and GND

Correct.

C412: between VccL/VccF (pin 20, 21) and GND
C413: between VccR (pin 10) and GND
C414: between VccC (pin 15) and GND

All these (VCCL/VCCR/VCCC/VCCF) are linked together and +5V. C410 which you already fitted Os-Con is also connected there. Better to replace C410 with Elna Silmic.

I have a few 470uF OS-CON (6 pcs) and Elna Silmic capacitors (2 pcs) left over.
I was wondering if I can solder them on top of the existing ceramic capacitor (i.e. in parallel config)?

That is very difficult to solder by hand. You might find that the small cap comes off the PCB even with just soldering on one side. Leave C412/3/4 alone.

Plus, the VCOM Cap (C411) you should really remove the small ceramic cap and put something better in place. I would stll recommend 1uF 63V Wima:

https://www.mouser.com/ProductDetail/WIMA/MKP2C041001N00MN00?qs=RB4whv9F6rzjnMhXY4f0hA==

Or is it better to replace the existing ceramic capacitors?

Only C411.

The others lave as is.

if you can find C404 (likely under the PCB and you have enough space, adding an extra os-con there would help, that is the clock supply.

BTW, "On the left you can also see the two supercapacitors (C210/226) that handle the filtering of the supply for clocks, DAC etc" <=== what are the capacitance of these supercapacitors?

I cannot remember, I used what was readily available at the time of design.

Maybe 2.2F/2.7V * 2 in series. They had a pretty fat inductor with some DCR in the +5V line to limit current.

Thor