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Old 21st July 2014, 05:29 AM   #21
fotios is offline fotios  Greece
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I'm looking at the Subbu design right now; it looks quite interesting. Maybe I'll make some changes...
And a "thank you" to Jean-Paul won't cost you nothing...
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Old 21st July 2014, 06:37 AM   #22
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I'm looking at the Subbu design right now; it looks quite interesting. Maybe I'll make some changes...
You are welcome although I learnt that native english speakers possibly mean something totally different when they say "quite interesting" . IMHO I think/know it will be hard to have the same or better quality certainly when using PCM5102A. There are more than enough mediocre performing DACs out there so please don't burn your fingers at "yet another DAC" by making the same design errors as others have done by omitting factors that define "quality". Quality sometimes can be determined in a few minutes extra thinking and a few extra pennies....

I hereby encourage and challenge you to surpass the Subbu V3 Of course I am willing to beta test your design if you like.
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Old 21st July 2014, 08:17 AM   #23
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You are welcome although I learnt that native english speakers possibly mean something totally different when they say "quite interesting" . IMHO I think/know it will be hard to have the same or better quality certainly when using PCM5102A. There are more than enough mediocre performing DACs out there so please don't burn your fingers at "yet another DAC" by making the same design errors as others have done by omitting factors that define "quality". Quality sometimes can be determined in a few minutes extra thinking and a few extra pennies....

I hereby encourage and challenge you to surpass the Subbu V3 Of course I am willing to beta test your design if you like.
Jean-Paul, i try to locate the initial thread for Subbu (any version) DAC without success. The only i found so far are 2 threads, a "Subbu v3 DAC building thread" and a "Modifying the Subbu v3 DAC" as well a group buy for PCBs. I came accross these threads but i could not locate any schematic. To be sincere, i am mostly interested for the WM8804 circuitry you use as in our project i use it but with the WM8741 DAC since i try to hit a total DNR close to 120dB. Could you please drop me a link where are the initial schematics? You should know that i am not so experienced with digital audio, simply it helps me a little my knowledge about digital circuits and microcontrollers.
Thank you!
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Old 21st July 2014, 04:11 PM   #24
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And a "thank you" to Jean-Paul won't cost you nothing...
Of course. Here's my thank you to everyone who helped me out or contributed to this thread.

I'm not sure if this is an official link, but there's a Google Drive folder online holding the Subbu DAC schematic, BOM, and layout files.
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Old 21st July 2014, 05:47 PM   #25
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Of course. Here's my thank you to everyone who helped me out or contributed to this thread.

I'm not sure if this is an official link, but there's a Google Drive folder online holding the Subbu DAC schematic, BOM, and layout files.
Its OK df audio.

Thanks for the link.
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Old 21st July 2014, 06:31 PM   #26
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It's OK. Don't know who did that as we are a bit reluctant posting our proven and tested schematics on line (just to avoid useless pages full of "why didn't you ..." ) Since it is there feel free to use it for inspiration, then reread post #3...
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Old 21st July 2014, 08:10 PM   #27
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Well the schematic is shared under Creative Commons, so someone with a copy could have legally posted it online.

For now, my plan is to stick with USB but leave a header on the board for connections to a seperate power supply. I read somewhere that it isn't good to place a transformer on the same board as everything else (due to EMI and similar), and having two boxes on my desk isn't much of a hassle anyways. An annoying thing with USB is the inrush current limit (post #4) that prevents me from using large caps - so if all goes well I might just switch to an AC supply altogether.

To be honest, my main concern with building an AC supply is the fact that I'll be working with transformers and high voltage from the power outlets. My parents just don't really want me to take the risk (I'm just a high school student) for safety's sake.

I suppose I could use a pre-built power supply, and as stated earlier just plug it in to the header on my board. However, most of the AC adapters on the market probably suck for audio use too, and won't really be much better than USB.
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Old 21st July 2014, 09:15 PM   #28
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Mmm, I am not in to legal stuff as I am not a lawyer (I have a soul, that is why). I only worked together with Subbu to make it a nice device

No fear for AC 230 or 115 V provided you have the knowledge and if you are not a teenager (you probably are, just checked on Google what high school is). Be aware of the risks, work tidy/safely and think + check twice and definitely have a fellow DIYer assist or guide you. I was working with mains connected stuff when I was 12 so it must be possible. Fear is your worst enemy, just check people that fear electricity. They get most shocks I would like to suggest a healthy respect for high voltages and an awareness to think of possible risks before you start on the job even if it is only connecting L and N.

Our PSU has been measured and it has 10 µV noise. I am very sure you won't get that result with USB adapter type power supplies. As you can see I tried to keep wiring to an absolute minimum to avoid risks for builders. If you use the recommended Phoenix connectors and work tidy it will be OK certainly when you have it checked by an experienced builder (before switching it on that is). When you will go on the path of designing good quality stuff you will have to make the switch to good power supplies one day anyhow. A good power supply is the heart of any audio device. The best DAC chip will not perform optimally with a mediocre power supply. In my personal opinion most care should go to the PSU... so in the light of audio fundamentalism you are already on thin ice. I hope you try to make your designs as good as possible. It can be very frustrating afterwards if corners are cut and your design will not perform as intended. It is bad enough that such is done is consumer gear so don't step into that trap when DIYing. See your designs as a kind of art form and every product as a "child" and you'll get the hang of it

Even when you still have doubts regarding AC I would include pads for a large filter cap and rectifier on the board. You can connect low voltage AC from a transformer in that case later of have it connected by an experienced person. No pads = no possibility.
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Old 21st July 2014, 09:35 PM   #29
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Yes, I am a teenager.

Is there any way to (using components) "clean" the noise out of a DC signal from a source such as USB or an AC adapter?

Last edited by df audio; 21st July 2014 at 09:37 PM.
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Old 21st July 2014, 09:57 PM   #30
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The best is to have a source with no noise

CLC filtering is quite effective as said before. Common mode coils....
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