What's the point of a iFi USB Power?

[Norton]

Keep wondering whether I should be buying one of these, but as I understand it, can only possibly make a difference where a dac relies on a PC for its power source? My current DAC (the input of an Oppo 105) plus all the ones I am thinking of upgrading to (including iFi's own) have their own mains or battery power sources so I can't see any advantage, or am I wrong?

[Ned Kelly]

Keep wondering whether I should be buying one of these, but as I understand it, can only possibly make a difference where a dac relies on a PC for its power source? My current DAC (the input of an Oppo 105) plus all the ones I am thinking of upgrading to (including iFi's own) have their own mains or battery power sources so I can't see any advantage, or am I wrong?

 

As luck would have it, I have a complete iFi stack plugged into my BDP-105D as I type this, but I'll leave the explanation to Michael Lavorgna -

 

iFi iDAC & iUSBPower | AudioStream

 

It's not about whether your DAC is powered or not - I even plonked down the extra cash for the iPurifier because I believe all this stuff matters, even if it's only one piece of the puzzle. I could demonstrate to you precisely how much noise the USB ports on my Win8.1 laptop are putting out very graphically with nothing more than my HRT microstreamer and I could show you how effectively the iFi stack cures that nastiness with the same DAC - this isnt snake oil.

[Norton]

I guess I'm having problems understanding this as, in iFi's own words:

 

"The most important feature of any USB audio device (USB DAC, USB Amplifier and USB Speaker etc.) is the power supply. The USB system as well as audio, carries its own power. Perfectly adequate to power anything from USB memory sticks to tablet computers; it falls far short from being a suitable noise-free power supply for high-quality music reproduction."

 

but any DAC I would use it with has its own independent power supply.

 

Then again if recommended anyway, I guess it's a fairly low-risk financial commitment...

[andyv]

..

I could demonstrate to you precisely how much noise the USB ports on my Win8.1 laptop are putting out very graphically with nothing more than my HRT microstreamer and I could show you how effectively the iFi stack cures that nastiness with the same DAC - this isnt snake oil.

 

It would be very interesting to see those demonstrations - any chance you could post the graphs?

[Miska]

I have measured differences with iUSB in use. Many DACs that power the USB side or entire device from USB bus power benefit from this.

[andyv]

I have measured differences with iUSB in use. Many DACs that power the USB side or entire device from USB bus power benefit from this.

 

I would be very interested to see those measurements also.

[tranz]

From an old IFI thread...

 

 

A few more amateur scope pics of the IFI impact.

 

1. Probe as antenna 5cm over IFI wall wart

 

[ATTACH=CONFIG]12672[/ATTACH]

2. Probe as antenna 1cm over cheap LPSU I use to power iUSB

 

[ATTACH=CONFIG]12673[/ATTACH]

3. Using IFI iUSB with probe on 5v USB wire and IFI wall wart

 

[ATTACH=CONFIG]12674[/ATTACH]

4. Using IFI iUSB with probe on 5v USB wire and cheap LPSU instead of IFI wallwart

 

[ATTACH=CONFIG]12675[/ATTACH]

5. Direct 5v USB connection from battery operated laptop (power lead unplugged) without iUSB

 

[ATTACH=CONFIG]12676[/ATTACH]

 

All using AC coupling, 2ms/div, 5mV/div, 1x probe. Wallwart and LPSU were plugged into a power filter one at a time.

[Miska]

I would be very interested to see those measurements also.

 

I used spectrum analyzer on the DAC output as usual. I didn't save the results, but I'll save next time I make some measurements.

 

The DSC1 results I posted were measured with DAC connected to iUSB.

 

Differences have been similar, to this case where Schiit Loki is fed by BeagleBoneBlack powered by two different kinds of PSU.

 

Here's the default kit wall-wart SMPS:

 

And here's with a Mascot 8421 PSU:

 

Difference is over 10 dB reduction in jitter.