[hisame]

Does ipower put Electrical and Magnetic noise back into the main power line like all other AC/DC adapter does?

 

[ginetto61]

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   

 

[Topspin70]

Anyone knows what the power consumption of the iPower 15V and 9V? I'm using them to power an iCAN SE and an iTube which are rated 12W and 7W respectively. So am wondering whether the PSUs consume their own power as well, and more specifically how much power? 

 

[Promenadeplatz]

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   

Only not working batteries do not produce riple and noise but once they are under load (powering whatever) they start producing noise, can go up to 50-150 mV.

 

[hisame]

  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   

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.

 

[ginetto61]

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.

 
Hi thanks a lot for the very kind and valuable explanation.
From what I understand it is easy to design and build bad smps.  
Instead is a real challenge to design and build very good one, much more than for linear power supplies where decent ones are quite common.
I like very much the smps concept for its compactness.
About the noise I can only hear it when is very evident.   But again from what I understand to get all the information embedded in a musical signal a very low noise is mandatory.
Otherwise the small level details, responsible for instance of effects like the soundstage rendition, can be buried in the noise carpet.  
Thanks a lot again,   gino 

 

[hisame]

A perfectly designed SMPS should has zero noise both way, 97% efficiency, massive power output (in 100s kw).
But it is very difficult to do, I remember 15 years ago when I was at uni,
I can actually design and build ClassAB PS with higher efficiency (75%) and lower noise then ClassD SMPS.
The SMPS I build was so noisy you literally can hear and feel the noise coming from it and it has only 72% of efficiency.
Most SMPS we bought these day has efficiency lower then 80% and they cover up the audible and mechanical noise using lot of glue.
So you basically got a low efficiency power supply that put out massive electrical, magnetic and radio noise which looks like a glue ball.
Which was why after a couple of years when glue got heat up and dry out by SMPS it start to make noise and vibrate.
But they can be cheaply made, and they are light and small.
 
You can buy really good SMPS like SMPS series from Hypex, 
SMPS from Hypex has the frequency generator trap inside a balance diode bridge, with neutral bridged and grounded.
With DC suppressor on mains side to prevent any DC feedback.
Plus filter on both side of the SMPS and the frequency generator act as isolation transformer.
So you get 92% efficiency, very low noise, power output from 400 w up to 3kw!!
 
Thing is you can buy SMPS today that has none measurable noise level, performs much better then LPS.
And they priced reasonable just not cheap, like iFi's iPower is the best example. 
But they look and feel like cheap counterpart, and people still think LPS is less noisier then SMPS.

 

[music_man]

no, switch mode can be much quieter than linear but not this. sorry. a good bench variac is much more money than this. this is certainly better than a stock wall wart but it is built to a price point. you could build something much beter but you will have to know how. or spend an amount you probably do not wish to. in fact that would be complete overkill for this situation. high end equipment with iec plugs has completely different options. even if you plug the cheap wall wart into a high end conditioner or online ups it will not remove the noise from it as the noise is being generated after the mains.

 

[iFi audio]

On the other forum there's been an interesting discussion about, yes, measurements. This time it was all about HP 3561A machine.... Anyway, here's our insight about it and some additional, iPower related things.
 
It's Friday and we had to bribe one of our junior techs with promises of copious servings of beer. So here goes......

First, we know this HP quite well. The 3561A is rated with a 1uV (-120dBV) measurement limit, not -146dBV(?), see here:

Agilent-3561A-Datasheet.pdfhttp://www.testequipmenthq.com/datas...-Datasheet.pdf

So it should give a pretty idea of the noise IF it substantially exceeds the specification. Noise above a few kHz is not significantly different from what is shown from the AP2 up to 6kHz. Settings such as window, FFT Bin size etc. do have an impact on results. Generally such ye olde devices need to be set to very narrow.

Second, it is mains powered with earth connection. This means it is subject to potential issues with ground noise of course respective of the measured device (iPower or not).

An easy test is to simply remove the probe from the +connection of the iPower and short it to the negative line, leaving everything else the same. If the noise is generated by the iPower itself, instead of being "instrument Ghosts" caused by an inadequate test setup, the noise will disappear completely.

Any remaining noise is the result of using an inadequate test setup. If you find that there is substantial noise in the 20Hz - 20khz range that disappears when the probe is removed from the positive line and shorted to the negative line, you may have a defective iPower, in which case we would like you to return it to us for testing/replacement.

If the noise is not caused by the iPower, you need to go through your test-setup.

Any noise generated by the iPower would have to be either an integer multiple of twice the mains frequency or at integer multiples of the switching frequency. The switching frequency is 100kHz , but is lowered lowered at light load for reduced EMI/Increased Efficiency. The minimum switching frequency at no load is 23kHz.

As a rule:
If you see significant levels of 50 or 60Hz (depending on local mains frequency) and the harmonics thereof not covered by the rectified DC ripple in the iPower (which would be 100/120Hz, 200/240Hz, 300/360Hz), that is 150/180Hz & 250/300Hz noise - you have ground noise of some description.

If you have significant noise at frequencies other 23kHz...100kHz (depending on load and input voltage) and integer multiples of these frequencies the noise is not generated by the iPower but conducted and/or received noise circulating through mains, device grounds and earth.

 

[G_T_J]

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!

 

[ADD]

Hi,
 
Can someone please let me know the cable length of the iPower supply please?
 
Thanks

 

[G_T_J]

  Hi,
 
Can someone please let me know the cable length of the iPower supply please?
 
Thanks

It is long enough. I don't have it right now to measure it but it has to be at least 2 meters long.

 

[ADD]

Thanks.

 

[iFi audio]

  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!
 

 
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.

 

[G_T_J]

   
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.

Thank you very much for the detailed explanation.
My project is ready and I'm going to power the Pi and LCD display from 2 different power supplies (iPower & a generic 2A power adapter for the display).
I have soldered a connector onto the Hifiberry board and therefore, the iPower powers both the HifiBerry and the Pi, bypassing the Raspberry Pi's voltage regulator. 
The result is very very good. I don't have any other low noise PSU or LPS to compare, but I have to say the combo sounds great!