DIY DAC with premade PCBs, some questions

There are still a lot of fake parts from the Chinese, and Aliexpress/ebay is to blame for that, which allows such things, that is, allows them to close a notorious company after a while, and immediately open a new one under a different name. And when we catch them in a scam, we only get a refund but no penalty to stop them from doing such things. I am surprised that their big manufacturers of original and licensed parts do not protest because it gives them a bad image. As long as there is no punishment, anyone can do what they want.
yep i also blame aliexpress management for that... its what its if no one enforces anything... or in a pseudo way (like banning accounts and they open new ones..)

did you guys test around with emi filters before the transformer primary?

thel's emi filter i have here... the power supply didnt excite me but the emi filter seems to work quiet well, i was searching for a emi board some time ago... there are 2-3 options but im unsure about the chinese ones..
 
I don't use EMI filters because some of them have a bad effect on the sound. I am ordering transformers with static shield (blind grounded layer) between primary and secondary. EMI is transferred capacitively from the primary to the secondary, the static shield eliminates much of that capacitance and drains interference to GND.

And I have a Quasimodo tester to properly determine the snubber for each secondary, so I eliminate the noise from the rectifier. I also practice CRC before the regulator. All together means that the regulator does not deal with HF noise but only with small 100Hz ripple which remains behind the CRC filtration.
 
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I don't use EMI filters because some of them have a bad effect on the sound. I am ordering transformers with static shield (blind grounded layer) between primary and secondary. EMI is transferred capacitively from the primary to the secondary, the static shield eliminates much of that capacitance and drains interference to GND.
i havent tried much but with what i have tried i believe people are overreacting to emi filters... imo the emi filtering benefit is far better than maybe some reduced dynamics you can easly (somewhat) eq again to your taste

tho from much testing with eq... you can compensate many tweaks with eq... its even not much thats needed 0,2db broadband eq can do alot..
for example one op amp sound a bit brighter vs the other... a low q high shelf filter with maybe -0,5db might already somewhat do the trick.... this doesnt completely hide the character of the tweak, but imo it can compensate it to a far degree

i played around with ferrite cables... there is kinda a german community around it you may can look it up ... it really does alot in terms of quieting the background etc...

tho im still unsure what different emi filter implementation sound like... im honest these 30 eur readymade industrial power cords that have emi filter really do sound kind of crap... but the "audiophile" thel emi filter was really good imo its just kind of expensive...
 
maybe with these chinese filters the best compromise is to use a one or two stage filter with high current capability, not the best filter characterists but from reading this probably would probably sound atleast acceptable, i might test this theory or test this one: https://www.audiophonics.fr/en/powe...ilter-anti-parasites-emi-230v-10a-p-2875.html but i expect its not better than these cheap power cords with multiple outlets
 
really curious what the seperate power supplys do tho...
They prevent ground loops through power supplies, they help prevent crosstalk due to audio signals drawing varying current in different parts of the circuitry, and or help prevent intermodulation and or noise due to unwanted coupling between different types of digital and analog circuitry. IME and IMHO no amount of extra bypass/decoupling caps, ferrites beads, etc., works as well separate, isolated power sources.

Regarding power filters, there a many different types of ferrite material. Some of them can introduce hysteresis noise into the system which can then cause various issues with the sound. Also, most small AC line filters only work over limited RF frequencies. The don't replace soft ferrite or laminated-steel common mode chokes on AC power connections which are used to help minimize AC power line-related ground loops.
 
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They prevent ground loops through power supplies,
how do you execute the grounding scheme? for true isolation the pcbs need to have a floating ground and not connected to chassi, right?

IME and IMHO no amount of extra bypass/decoupling caps, ferrites beads, etc., works as well separate, isolated power sources.
i never made a good comparison, i just was suprised how well this supercapacitor filter performs... and how close it actually bring SMPS and linear power supply to the same-ish performance
https://de.aliexpress.com/item/1005004413679736.html

... i might play around with these: https://de.aliexpress.com/item/1005002737105856.html for 5V and 3,3V lines
 
i made quick draft for a universal LM317 board...

the sparkos discrete voltage regulators need actually some modifcation to the LM317 circuit, thats what the 2 switches do, since the ADJ pin becomes GND on the sparkos, this might be also a better approach if i wanna do my own regulators

1uF kemet tantalum Cin and Cout caps, kind of universally, tho im still thinking about adding a spot for a larger electrolytic cap, but i read LM317 dont like to large output capacitance so im kinda unsure.. tho i would rather optimize towards better/newer design than LM317...

i could probably leave SW2 out but i rather disconnect it completely if i can..
 

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how do you execute the grounding scheme? for true isolation the pcbs need to have a floating ground and not connected to chassi, right?
AC line ground must be connected to the chassis. Circuit ground is connected to AC line ground through a hum-breaker circuit, more or less like this (resistor value may sometimes be up to 100R):
1712328319581.gif


For any commercial chassis in your system not made that way, and or for additional minimization of AC power ground loop problems, a used "Monster HTPS 7000 MkII Signature Edition" power conditioner is very good. It was designed for Monster by our own Richard Marsh, and Demian Martin ( @1audio ). They typically go for around $500 on ebay when available. The earlier HTPS 7000 versions are also very effective, but the recommended one is best (and has three GFI duplex AC outlets on the back, for the three transformer balanced circuits).
 
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A standard US 120VAC wall socket breaks-down/flashes-over at, IIRC, around 3kv. In case of a lightening strike in the nearby area, the socket flashover voltage may be the last line of protection for connected devices. Thus a 4kV rating may be enough insulation to prevent breakdown of the transformer from primary to secondary in such a case.

The higher voltage insulation may also be more durable, long-lasting, or have other useful properties besides its breakdown voltage rating. You would have to ask Torroidy about that.
 
A standard US 120VAC wall socket breaks-down/flashes-over at, IIRC, around 3kv. In case of a lightening strike in the nearby area, the socket flashover voltage may be the last line of protection for connected devices. Thus a 4kV rating may be enough insulation to prevent breakdown of the transformer from primary to secondary in such a case.

The higher voltage insulation may also be more durable, long-lasting, or have other useful properties besides its breakdown voltage rating. You would have to ask Torroidy about that.
the standard configuration for audio grade transformers is SYN-SHIELD and 4kV Isolation between primary and secondary, probably the important one ... but i could add SYN-SHIELD (some kind of copper mesh EMI shield) between secondarys or/and 4kV isolation

TS 400VA
PRI: 230V
---------------------------- 4kV Isolation
---------------------------- SYN-SHIELD
SEC I: 8V (5A)
SEC 2: 8V (5A)
SEC 3: 8V (5A)
SEC 4: 8V (5A)
---------------------------- SYN-SHIELD
SEC 7: 15V (5A)
SEC 8: 15V (5A)

is probably good enough i think

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the modushop case just arrived yesterday... https://modushop.biz/site/index.php?route=product/product&path=171_229&product_id=158
not that impressed, the looks are ok but screws are sparse, most of them are simple steelsheet screws and it really does ring... tho it feels quite rigid but the top and bottom cover can definitely take some bitumen...

kinda thinking on getting better another one.. like this one: https://modushop.biz/site/index.php?route=product/product&product_id=446
but i might still use the case... its not that bad but also not perfect... and i kinda thought the screw in of the baseplate(which is the most rigid part btw) would be more easy, one its in its hard to get out again... specially with cables etc

but i think its gonna get tight with 8 secondarys in either of these
 
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Be sure to get it, it is grounded to the IEC GND and prevents the capacitive transfer of EMI interference from the primary to the secondary. You don't need an EMI filter which usually affects the sound badly.
between primary and secondary it will be 100% there because this is stock configuration for toroidy audio grade transformer, i could take without but i wont, the question is if i should add the SYN-Shield between the secondary windings, or like in my example above where its only aditionally between "digital" secondarys (8V) and "analog" secondarys (15V)
 
Hi ! This one has just been released.
I ordered one to see... 250 Euros .Will the DAC experts tear me down?
I like isolated ground planes, based on daughter cards and separate power supplies....


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I am assembling a multichannel dac based on an AK4493seq chip from this brand and the first results are nice!

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