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In Reply to: RE: Power supplies in dacs posted by beppe61 on July 19, 2015 at 23:37:30
best DACs have separate power supplies for analog, digital,DAC conversion, and thins like the timing circuit.
Each section will cross contaminate each other if a single power supply is used, ot matter how large, and separate smaller supplies is the key with isolation between them
Follow Ups:
Hi and thanks a lot for the valuable advice.
I think it would be difficult to do that ... but i will keep it in mind.
I have some of this cheaps dacs found on ebay
They usually comes with a cheap wall power adapter.
Just using a better linear supply gives some benefits.
The idea is to extract the board and put some nice and bigger uF in strategic places and use a very low noise linear ps.
First experiments are promising. Noise fights music.
Thanks again.
Kind regards,
bg
Where do you think nose in a DAC is being sourced? The digital bit stream entering the unit contaminates the analog stage and everything else both inside the chassis and including the power supply .
If you have an old TV set, try placing a portable CD player close to the antenna: your picture will immediately show tremendous aberration as the RF will interfere with the reception. Initial CD players used plastic chassis until complaint to the FCC forced them to stipulate that the chassis be made of metal and RFI emission be reduced to certain standards, the main reason why so many early players had optical outputs.
Simply increasing the power supply current does help, but you are not addressing the main issue, at least IMHO
" Where do you think nose in a DAC is being sourced? "
My take is mainly from the power supply but i could be wrong.
Unfortunately i do not have a scope to see how dirty are my mains.
But i have noticed that during sunday the sound is better.
I live in an semi-industrial area.
" The digital bit stream entering the unit contaminates the analog stage and everything else both inside the chassis and including the power supply .
If you have an old TV set, try placing a portable CD player close to the antenna: your picture will immediately show tremendous aberration as the RF will interfere with the reception. Initial CD players used plastic chassis until complaint to the FCC forced them to stipulate that the chassis be made of metal and RFI emission be reduced to certain standards, the main reason why so many early players had optical outputs "
I see. So the digital chips are RFI generators ? this complicates the all issue.
I am using a usb to spdif converter that has isolation transformers on the digital outs (see picture) ... could this be enough ?
" Simply increasing the power supply current does help, but you are not addressing the main issue, at least IMHO "
actually i was focusing more noise than current.
A better PS could suppress more noise coming from the mains and generate less noise by itself. But i understand that i have to study more.
At least i have to try before modding anything.
Thanks a lot again.
Kind regards,
bg
Again in digital equipment noise, in effect, is self generating. You got clock chips, sometimes several, running at RF frequencies. Most are metal covered for some shielding, but I like to ground the cases ( some players and DACs do that, BTW). I believe your unit has three clocks.
The digital processing chips themselves are generally plastic encased and thus RFI can easily enter and exit the chips as they process the bit stream data entering the unit.
All the essential circuits work with RF frequencies and they are not synchronized. They radiate within the chassis and they contaminate all power supplies.
The key IMHO, is to attack the source. Obviously you need the digital data, but it is imperative that you try and contain the "RF radiation" they produce.
Easiest way to limit them is to cover all chips and semiconductors with ERS. There is a reason why they are shielded, and I can see some kind of circuit under neath.
The boxes while acting as a shield are not as effective as ERS, because their reflective surface can actually "bounce" some RF off. Again the lowly HK players used a box but lined it with felt to be more absorbent. You can line the boxes with ERS too.
Some have simply lined the entire chassis with ERS, but that does NOT stop the internal RF reflections from bouncing around and contaminating adjacent chips and circuits. also be aware that many DAC's employ a filter on the analog output stage to roll off RF. I've seen this on Regas and even the Esoteric machines. Using ERS with out disabling the roll off circuit simply makes the unit dull.
I did shielding like I described on an Esoteric unit and it indeed sounded dull till I lifted the small ceramic cap off the output stage. The unit then opened up, with an extremely airy quality and a tremendous sense of depth.
Hi ! thank you very much indeed for the very valuable advice.
I will try some of these EMI/RFI pads for sure ... placing them on the digital chips.
In the meantime i have found a very interesting discussion where you were involved here
http://www.audioasylum.com/cgi/t.mpl?f=tweaks&m=190998
I start studying more seriously the subject.
My main device is now this usb to spdif/aes/optical converter.
I like the fact that gives me the opportunity to link to my pc any dac around and listen.
It is a key device also because in the end it sets the clock.
I have the feeling that is well designed but i have already seen some possible upgrade (in the power supply actually).
Surely addressing the RFI noise it will give further benefit.
I will do the same on the dacs.
Thanks a lot again for the very helpful advice.
Kind regards,
bg
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