Measuring the iPOWER - Much Ado about Nothing (part 4 uploaded and complete)

[firedog]

Measurements of Sonore microRendu Streamer | Page 34 | Audio Science Review (ASR) Forum

 

See post 669.

 

 

1) Amir claims using the power transformer makes no sense, as this is not how the product will be used in real life.

2) Amir did the same measurements, with the same metodology using the Regen instead of the mR, and didn't find the noise he previously reported. He says that leads to the conclusion that there is no ground loop in his measurements of either device, but that the problem somehow comes from the combination of the iPower and the microRendu.

3) He says iFi's pdf says nothing to contradict his results.

[BobSherman]

Measurements of Sonore microRendu Streamer | Page 34 | Audio Science Review (ASR) Forum

 

See post 669.

 

 

1) Amir claims using the power transformer makes no sense, as this is not how the product will be used in real life.

2) Amir did the same measurements, with the same metodology using the Regen instead of the mR, and didn't find the noise he previously reported. He says that leads to the conclusion that there is no ground loop in his measurements of either device, but that the problem somehow comes from the combination of the iPower and the microRendu.

3) He says iFi's pdf says nothing to contradict his results.

 

1. Stupid people say stupid things.

2. see #1

3. see #2

[Superdad]

Well the issue of leakage currents is real--but ignored or not well understood even by many engineers. The problem exists with both switching and linear supplies, just to different degrees, and even a big isolation transformer does not stop it.

(Though a thick copper grounding braid between PC and test gear will offer a lower impedance path and should reduce the presence of AC-cycle-harmonics.)

Everyone's audio system grounds bounce up and down with this stuff--get used to it!

[MG32]

1. Stupid people say stupid things.

2. see #1

3. see #2

 

Couldn't have put it any more succinct, in the face of pure logic, there are those who still refuse to face the facts

[Paul R]

Measurements of Sonore microRendu Streamer | Page 34 | Audio Science Review (ASR) Forum

 

See post 669.

 

 

1) Amir claims using the power transformer makes no sense, as this is not how the product will be used in real life.

2) Amir did the same measurements, with the same metodology using the Regen instead of the mR, and didn't find the noise he previously reported. He says that leads to the conclusion that there is no ground loop in his measurements of either device, but that the problem somehow comes from the combination of the iPower and the microRendu.

3) He says iFi's pdf says nothing to contradict his results.

 

There does not seem to be much Audio Science on that site - just a lot of hot air...

[muski]

Thanks for an excellent and informative thread.

 

Wondering if someone could please educate me on ground loops.

 

I have an iFi 9V powering a µRendu connected to a Mojo. When my Mojo is off, I can hear a loud buzzing noise in my headphones. I assume this is a ground loop and not 'noise'?

 

Yet this doesn't happen with an HD-Plex, nor a cheap 9V power supply. Is there something different in their design? Also, when I use a shielded Ethernet cable, it mysteriously goes away.

 

Does it have something to do with the Mojo not being grounded? Is one component the cause, or is it the whole system that's causing this buzzing? Would this ground loop adversely affect sound quality even when the Mojo is on?

 

Any enlightenment appreciated!

 

Thanks,

muski

[AMR/iFi audio]

Thanks for an excellent and informative thread.

 

Wondering if someone could please educate me on ground loops.

 

I have an iFi 9V powering a µRendu connected to a Mojo. When my Mojo is off, I can hear a loud buzzing noise in my headphones. I assume this is a ground loop and not 'noise'?

 

Yet this doesn't happen with an HD-Plex, nor a cheap 9V power supply. Is there something different in their design? Also, when I use a shielded Ethernet cable, it mysteriously goes away.

 

Does it have something to do with the Mojo not being grounded? Is one component the cause, or is it the whole system that's causing this buzzing? Would this ground loop adversely affect sound quality even when the Mojo is on?

 

Any enlightenment appreciated!

 

Thanks,

muski

 

 

From afar, the problem is the lack of ground/earth in this system, if you open a Support System Ticket, we can send through the earth trouble-shooting note.

 

It CANNOT be a ground loop, as there is no ground!

 

Cheers.

[muski]

Will do. Thanks!

[rickca]

@AMR/iFi audio ... is the 9v/2A iPower compliant with the Level VI energy efficiency standard for external power supplies?

[rickca]

@AMR/iFi audio could you please answer my question in post #34.

[AMR/iFi audio]

@AMR/iFi audio could you please answer my question in post #34.

 

We missed the reply. We will ask R&D and revert as soon as possible.

[AMR/iFi audio]

@AMR/iFi audio ... is the 9v/2A iPower compliant with the Level VI energy efficiency standard for external power supplies?

 

Our current underlying PSU Solution (using Fairchild mW saver technology) is compliant with U.S. DoE Level VI Energy Efficiency requirements.

 

More on Fairchild mW saver:

 

 

https://www.fairchildsemi.com/product-technology/mwsaver/

[rickca]

Thanks!

[Kingpin]

Do you also have a fft plot 0-100kHz instead of the 6kHz plot ?

 

If i measure with my HP Spectrum Analyzer (calibrated, -146dB noisefloor, lower as 1uV) the ifi ipower from 0-100kHz the noise is much higher then 1uV (measured at the end of the dc cable with 50 ohm load at 9V).

[AMR/iFi audio]

Do you also have a fft plot 0-100kHz instead of the 6kHz plot ?

 

If i measure with my HP Spectrum Analyzer (calibrated, -146dB noisefloor, lower as 1uV) the ifi ipower from 0-100kHz the noise is much higher then 1uV (measured at the end of the dc cable with 50 ohm load at 9V).

 

From afar, it is difficult for our techs to give a prognosis. We’d have to see the measurements and measurement setup to be sure.

 

But here goes…

- For reference, the common mode noise for any power-supply (linear or switching) without a safety earth connection and in compliance with EMC Regulations is 1/2 of the mains voltage and any common mode AF/RF noise on the line, which can be up to several volt.

- If attempting to measure microvolt levels of noise this implies a common mode rejection of noise at the mains frequency of greater than 160dB and likely at least 120dB at 1kHz - 20kHz.

- The AP2 we have ultimately uses NE5534 Op-Amp's to create handle common mode rejection so it falls well short of the required Common Mode rejection and care needs to be taken to avoid measuring common mode noise in the actual measurement.

Hence, we recommend the use of a balancing transformer and/or earthing the ground of the DC output of the power supply.The key here is that at the noise levels being measured, great care is needed to avoid 'instrument ghosts' (please refer to the iPOWER article).

 

Even Oscilloscopes with 1mV input sensitivity (meaning they can reliably measure down to around 1mV or 1000 times greater than 1uV can readily be made to show all sorts of noise on screen with the actual probe short circuited, meaning the actual input signal is dead short.

[Kingpin]

From afar, it is difficult for our techs to give a prognosis. We’d have to see the measurements and measurement setup to be sure.

Measured with the 3561A.

Connect iFi ipower end of dc cable to a 50Ω load (did you measure at the end of the dc cable ?).

And of course i removed the probe earth wire and measure with the probe tip (right image).

 

 

 

Hence, we recommend the use of a balancing transformer and/or earthing the ground of the DC output of the power supply.The key here is that at the noise levels being measured, great care is needed to avoid 'instrument ghosts' (please refer to the iPOWER article).

I know for best performances (and safety) to use a balancing (isolation) transformer. But the ifi ipower isn't earthed too, so connecting ifi ipower dc out to earth (could) gives you unwanted ghosting and for 'real world' statistics (who has a isolation transformer inhouse?) i do it without the isolation transformer because it gives you fairer statistics.

[AMR/iFi audio]

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/datasheets/Agilent-3561A-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.

[AMR/iFi audio]

Boys and girls, just a quick reminder. We'll attend to UK's world famous Sound & Vision - Bristol Show. As per usual, we'll show a new thing or two there, so if you're around, please come and visit us!

The date: 24th - 26th of February

The place: Marriott City Centre Hotel, Lower Castle Street, Bristol, BS1 3AD

The brand: iFi Audio / suite 11

For further info, please take a look here:

http://www.bristolshow.co.uk

See you on the spot!

[crion]

Greetings ifi!

 

I require 12V/1.8A and ordered the ipower 12V/1.8A from my local well-equipped store.

 

But on the box it says to my amazement 12V/1.1A!

 

I asked the store to open it and check the wall-wart. Lo and behold it still said 12V/1.1A.

 

What is going on here?

 

Website:

Input: 100-240VAC

 

Output: 5V/2.5A; 9V/2.0A; 12V/1.8A; 15V/1.2A

[Liam]

Greetings ifi!

I require 12V/1.8A and ordered the ipower 12V/1.8A from my local well-equipped store.

But on the box it says to my amazement 12V/1.1A!

I asked the store to open it and check the wall-wart. Lo and behold it still said 12V/1.1A.

What is going on here?

Website:

Input: 100-240VAC

Output: 5V/2.5A; 9V/2.0A; 12V/1.8A; 15V/1.2A

It appears that your store is offering you the original iPower. The iPower was upgraded quite see time ago.

My one had a yellow sticker on the front of the box saying 12V/1.8A and a sticker over the rear specifications on the box giving the new raised specs. for the other voltages as well.

There were other performance improvements as well. Go here to view.

http://ifi-audio.com/portfolio-view/accessory-ipower/