hisame
New Head-Fier
- Joined
- Nov 10, 2009
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Does ipower put Electrical and Magnetic noise back into the main power line like all other AC/DC adapter does?
Hi ! sorry to jump in with a question.
I think that the noise forward is more detrimental than the noise back in the mains. Am I wrong ?
Another point. I have the feeling that SMPS are quite bad at filtering noise coming from the mains. Am I wrong again ?
I think that is important at psu level to stop any noise coming from upstream (i.e. mains) and avoid injecting new noise generated by the psu in the audio system.
I think that this of the noise is a very important issue, especially with digital.
And could be the reason why some digital sound unconvincing.
Supply it with a battery and listen ...
I did some test on a simple usb to spdif converter. Astonishing result.
regards, gino
Hi ! sorry to jump in with a question.
I think that the noise forward is more detrimental than the noise back in the mains. Am I wrong ?
Another point. I have the feeling that SMPS are quite bad at filtering noise coming from the mains. Am I wrong again ?
I think that is important at psu level to stop any noise coming from upstream (i.e. mains) and avoid injecting new noise generated by the psu in the audio system.
I think that this of the noise is a very important issue, especially with digital.
And could be the reason why some digital sound unconvincing.
Supply it with a battery and listen ...
I did some test on a simple usb to spdif converter. Astonishing result.
regards, gino
Originally Posted by hisame /img/forum/go_quote.gif
Noise is bad either way. By principle well designed SMPS should be filtering noise from main by default. Because it first change in coming sine wave to very high frequency pulse (make noise deliberately). Then it filter the pulse out by high speed capacitor (noise filter) and it ties natural with ground.
On paper well designed SMPS should filter out any common mode and differential mode noise. Because by ties natural with ground with a diode, all pulse should only go forwards.
And with low pass filter designed for the pulse generator should give you nothing but DC. But we all know it does not do that, because nothing works as theory.
The problem with poorly designed SMPS is basically a very bad frequency generator.
Not only it generated the designed frequency but also also generated other frequency in near by band.
And it send the pulses not only one way but two ways.
Basically makes SMPS a noise generator, which is the kind of SMPS we buy everyday. For good SMPS the important thing is not noise going forward. Because that will have to go through low pass filter, so noise is reduced anyway. But noise injecting back, because that just raw noise going down your other components. Which would effect you whole rack of HiFi components.
That is why I asked iFi which kind of back injection of noise with iPower.
Do I still need filter separation like my other SMPS.
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Hi,
Can someone please let me know the cable length of the iPower supply please?
Thanks
As there is an iFi contributor here, I thought I'd ask. Of course any user who knows is welcome to help!
I have an iFi 5v 2.5 A PSU and want to power both my Pi / Higiberry as well as the Official RPi 7 inch screen.
For that reason I want to run from the PSU 2 separate micro USB leads with male connectors, one for the Pi itself and one for the display board.
1)Am I going to lose the advantage of low noise floor if I do this hack?
2)If not, is there an adapter like this - prefferably official? (female DC jack 5.5x2.1 to dual male micro USB)
3)Can the PSU handle the power requirements? I'm pretty sure it can as the Pi draws less than 700mAh, the Hifiberry Dgi+ Pro <50mAh and the Official 7 inch display tops at 500mAh according to the spec sheet but anyway I thought I'd ask just to be on the safe site!
Thanks!
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Yes, you are going to loose it.
OLED and similar multiplexed LED dispalys are extremely noisy and put a lot of switching/muliplexing related noise back into the power supply lines. This is the origin of the 'urban myth' that states 'LED's are bad for sound quality', because their peculiarities are not understood and addressed during system design.
While the iPower will be able to kill a fair bit of this noise, the resistances of the DC cable of the iPower and the contact resistances of the adapters will limit what it can do and a considerable amount of the display switching noise will be left to flow to the DAC board and the Pi.
So when using a LED/OLED display with any of these small computers, it is highly recommended to power them separately from another power supply and to power only the small computer (and optionally audio/dac shield) from the iPower. Ideally one may even use another separate power supply for the DAC. So one might use the original small computer PSU to power the display and two iPower - one for the small computer and one for the DAC.