The iFi iUSB Power Supply - Neat Tweak & Upgrade for USB DAC

[Blake]

...just found this link:

 

iFi-audio

[tubesound]

I will try it in my system soon. Even if the USB chip is not powered from computer, I still think the iUSBPower will surely help by:

 

1. breaking the noisy ground loops between the PC and the DAC

2. eliminates cross contamination of the data lines (D+/D-) by the noisy the power line (VBus).

3. Even the DAC may not be powered from the PC, it's USB input receiver IC is often powered from the PC or has a hard connection with the noisy power line (VBus) from the PC.

 

The second point above may need more explanation: basically as the 4 wires (VBus, GND, D+,D-) in USB cable are closely blundered together, there will surely be crosstalk contamination happening. But if the power is very clean, pure DC, no AC noise at all, then it can't contamination the data lines (D+/D-), so the data lines are more clean, less jitter etc. Just like optimising a computer for audio playback, which in a sense is optimising the quality of the power lines and data lines on the USB.

 

iFi website is up: iFi-audio iUSB and they explained similar points to your #1 and #2.

[mdkim]

Thanks for the clarification. My order is now placed.

 

Is the supplied cable a standard USB cable or is it specific to the unit? I am also curious if an upgraded cable will still provide "some" sonic benefits (on both ends assuming they are the same) or if it's now rendered moot.

[One and a half]

USB uses a differential transmission system, the same principle as XLR based system for analog. Any noise can crosstalk on the cable which if you have a unbalanced (2 wire) system, does cause problems and it's difficult to remove, since the noise has to be filtered along with the signal.

Differential mode means that noise is induced (or conducted) is assymetrical. Any assymetric signal is ignored by the differential receiver as mathematically incorrect.

 

Here is a bit more on how the differential system for USB works. (Link)

 

The receiver defines a differential ‘1’ as D+ 200mV greater than D- and a differential ‘0’ as D+ 200mV less than D-. The polarity of the signal is inverted depending on the speed of the bus. Therefore the terms ‘J’ and ‘K’ states are used in signifying the logic levels. In low speed a ‘J’ state is a differential 0. In high speed a ‘J’ state is a differential 1.

 

USB transceivers will have both differential and single ended outputs. Certain bus states are indicated by single ended signals on D+, D- or both. For example a single ended zero or SE0 can be used to signify a device reset if held for more than 10mS. A SE0 is generated by holding both D- and D+ low (< 0.3V). Single ended and differential outputs are important to note if you are using a transceiver and FPGA as your USB device. You cannot get away with sampling just the differential output.

 

The low speed/full speed bus has a characteristic impedance of 90 ohms +/- 15%. It is therefore important to observe the datasheet when selecting impedance matching series resistors for D+ and D-. Any good datasheet should specify these values and tolerances.

 

High Speed (480Mbits/s) mode uses a 17.78mA constant current for signalling to reduce noise. <--- Important

 

You look at these levels, and they are 200mV, in analog terms these are huge audio pressure levels. The 5V supply is intended for devices away from the computer to be powered, like corded mice and keyboards. Dacs on the other hand have their own reference voltage to pull up or down the differential signals, and use the 0V (black wire) from the computer and it's own 0V, so the two are on the same level as they have to be.

 

I can fully understand to have a separate power supply for devices, such as the Stello U3 and Audiophilleo, as these models derive their power from the 5V supply from the computer. Audiophilleo has it's own optional power supply, preciesly to overcome the noise problem and it does work (see Head-fi). Some users use a low noise USB hub to break the lines, however their use has mixed results. Some users report worthwhile changes, others report little or no difference, the usual expectation and subjective bias at play, and some electrical characteristics thrown in as well.

 

As far as noise then travelling along data lines and affecting the receiver, the differential mode can fix that to a degree, but we are talking audio another dimension again, it's a matter of degree and perception.

 

The other path for noise to travel is the case of the USB connector, or the shell which electrically connects the computer to a DAC or converter, now here is where the USB cable can make a difference or just by using a separate power supply, that with some simple circuitry can kill noise from the computer on the shield, since it can be filtered from either device without it causing any impact on the signal itself.

 

USB galvanic isolation is achievable, but here you start to affect the signal. Not by all means dissuading the iFi as not worthwhile, anything that breaks the noise is worthwhile and there are alternatives, pity there's no magic bullet.

[27Globes]

Thanks for the clarification. My order is now placed.

 

Is the supplied cable a standard USB cable or is it specific to the unit? I am also curious if an upgraded cable will still provide "some" sonic benefits (on both ends assuming they are the same) or if it's now rendered moot.

 

It is my understanding that an upgraded cable aka Acoustic Revive will still definitely provide sonic benefits... and I would hope so at that price

[27Globes]

iFi website is up: iFi-audio iUSB and they explained similar points to your #1 and #2.

 

I also suggest that even with the ground-lift disabled there is also a greater common mode impedance and greater noise transmission resistance with the iUSBPower inline.

[Supreme Dalek]

I was talking with Vince earlier today and he told me that AMR are planning on keeping their answers to questions re Ifi on their Ifi Audio Face Book page. Not saying that AMR won't answer questions elsewhere but AMR feel that a central resource for answers and place for questions to be asked means the information can be shared among many.

 

He told me that there is an answer re how the iUSB works being prepared at the minute.

 

http://www.facebook.com/iFiAudio

[Boris75]

Has someone compared this iFi USB power supply to an AQVOX? I am asking the question because I am currently using an AQVOX between my Macbook and my Audiophilleo AP2. I am pleased with it, but if this new toy can bring some improvement, I would be tempted to go and get it.

[27Globes]

Has someone compared this iFi USB power supply to an AQVOX? I am asking the question because I am currently using an AQVOX between my Macbook and my Audiophilleo AP2. I am pleased with it, but if this new toy can bring some improvement, I would be tempted to go and get it.

 

I believe that the iUSB was introduced at RMAF... and it may be a little too early in its marketplace entry for comparisons.

[DM]

Boris, I am looking for a USB power supply too. The AQVOX states what it has ~1mV output noise, the iFi iUSBPower states it has 0.1uV noise, so from the spec (1mV = 1000uV), you can work out the difference in performance.

 

The AQVOX seems using a normal generic 317 regulator (which has a noise performance of a few mV normally), but the iUSBPower seems much more complicated. Well, to get a noise performance that is quieter than 9V battery is not an easy job, more info here:

 

[DM]

forgot to mention, the iUSBPower also has IsoEarth to break the ground loops, which I think it's fairly interesting.

[ted_b]

So:

1)I have a Meitner MA-1 DAC that requires 5V USB power from the computer end.

2) my computer, the CAPV2+ Win 8 music server I have detail ad nauseum here at CA, has the PCIe SotM-exp USB card that allows for separate 5V dc (battery or AC) powering, if needed..via its own dc output jack.

3) I am letting my large hi-end linear Hynes SR7-EHD (set to 12V) power the Intel mobo which then powers the SotM card (via internal molex connector)

 

Now, I am not saying that I'm getting noise, as my setup sounds glorious. But...as a dyed-in-the-wool audiophile I am always looking for improvement. With the several options available (good overall linear power from Hynes as I'm doing, separate 5V USB power via SotM, or separate 5V USB power further downstream from the ifi device), which of these would you guys think is theoretically (or on paper IOW) the right and cleanest way to go to get the Meitner the least noisy USB signal?

 

I would postulate that the SotM 5V choice would be the cleanest simply cuz it involves fewer connections, no extra USB cable (as per ifi) but maybe I am truly missing something. Also, no idea what I'd pair with the SotM to power it (at say, $200 or less).

[tubesound]

So:

1)I have a Meitner MA-1 DAC that requires 5V USB power from the computer end.

2) my computer, the CAPV2+ Win 8 music server I have detail ad nauseum here at CA, has the PCIe SotM-exp USB card that allows for separate 5V dc (battery or AC) powering, if needed..via its own dc output jack.

3) I am letting my large hi-end linear Hynes SR7-EHD (set to 12V) power the Intel mobo which then powers the SotM card (via internal molex connector)

 

Now, I am not saying that I'm getting noise, as my setup sounds glorious. But...as a dyed-in-the-wool audiophile I am always looking for improvement. With the several options available (good overall linear power from Hynes as I'm doing, separate 5V USB power via SotM, or separate 5V USB power further downstream from the ifi device), which of these would you guys think is theoretically (or on paper IOW) the right and cleanest way to go to get the Meitner the least noisy USB signal?

 

I would postulate that the SotM 5V choice would be the cleanest simply cuz it involves fewer connections, no extra USB cable (as per ifi) but maybe I am truly missing something. Also, no idea what I'd pair with the SotM to power it (at say, $200 or less).

 

I'd like to suggest you to try out the external power to STOM USB card first. I read somewhere that people recommend Jomeco: Jameco Electronics - Electronic Components Distributor

[4est]

I would postulate that the SotM 5V choice would be the cleanest simply cuz it involves fewer connections, no extra USB cable (as per ifi) but maybe I am truly missing something. Also, no idea what I'd pair with the SotM to power it (at say, $200 or less).

 

This situation seems like the perfect spot for a Y cable (or eq), a LiFePo4 battery and a smart charger in lieu of either the iFi or SOtM options.

[ted_b]

Thanks. So you think a $12 Jameco wallwart (albeit linear) would provide better cleaner power than having the Hynes beast power both (or is the Hynes simply powering the mobo, and from there the mobo dirties up everything it powers)?

 

I have an email into Jesus (Sonore US) for the same question; I may demo his battery option but would love not to spend another $400 (the Hynes is big buck and frankly sitting at idle). Thanks.

 

P.S. I'm also getting my Hynes SR3-12 back in a couple days (will sell it, maybe with the Auraliti). But I assume giving that SOtM dc input 12V is a no-no.

P.P.S. Sorry for the hijack from ifi!

[ted_b]

This situation seems like the perfect spot for a Y cable (or eq), a LiFePo4 battery and a smart charger in lieu of either the iFi or SOtM options.

 

Explain. If not using ifi type device (or AQvox, etc) or SotM external ps options where would USB power come from (connections wise). Sonore sells smart charger but it uses the SOtM option, obviously.

[4est]

Ted_b: The Y cable would break the 5v connection on one leg, supply 5v from the battery in the other feeding both into the DAC. You asked for a sub $200 option, and that popped into my mind straight away. Would it be as good? I dunno... but it should be under $200, under $100 DIY. This is expecting that if you are willing to put a computer together, you are also willing to plug some other bits together too.

[ted_b]

I'm still not sure how a Y cable accomplishes that. A Y USB cable? Doesn't exist except for the dual conduit ones I've tried...which still require power from somewhere (ifi, battery, SotM), since my CAPS has only one SOtM usb out. Not for me...I am not going to forego my USB cable and build some new cable setup, etc. The SoTm solution is wayy simpler to me, but I might be missing something. I have a USB cable that is wonderful. Thanks.

[4est]

Ted_b:

 

I wasn't suggesting that you pursue this. You seem very happy with your present solution. I was mearly presenting this as an option to those whom read this thread as they might be interested in alternatives to either the SOtM or iFi.

[ted_b]

? I am looking to persue something, or I wouldn't have posted (and since your post used my quote as a starting point I assume you were also talking to me, along with the general thread)..

[tubesound]

Thanks. So you think a $12 Jameco wallwart (albeit linear) would provide better cleaner power than having the Hynes beast power both (or is the Hynes simply powering the mobo, and from there the mobo dirties up everything it powers)?

 

I have an email into Jesus (Sonore US) for the same question; I may demo his battery option but would love not to spend another $400 (the Hynes is big buck and frankly sitting at idle). Thanks.

 

P.S. I'm also getting my Hynes SR3-12 back in a couple days (will sell it, maybe with the Auraliti). But I assume giving that SOtM dc input 12V is a no-no.

P.P.S. Sorry for the hijack from ifi!

 

I don't know but just guess there might be pollution somewhere from mobo to SotM? The 5V linear regulated Jameco is only $8.95.

 

If your MA-1 DAC doesn't use the USB power from the PC, I think this cable might be a good idea to try before the Jameco purchase: Acoustic Revive USB Cable USB1.0SP 1m Independent Power Signal Line Separate A | eBay. Yes I know this Japanese cable is very expensive but it's very easy to make your own as well (just buy two cheap USB cables and one USB A head connects power lines and the other A head connects the signal lines). My DAC doesn't use the USB power from the PC; I'm gonna make such a cable soon.

 

Then if you buy an isolation tranformer for you MA-1 DAC, I think the noise from power and signal should be taken care of. ifi iUSB may not be needed.

 

Anyway, that's my plan.

[ted_b]

I don't know just guess there might be somewhere pollution from mobo to SotM? The 5V linear regulated Jameco is only $8.95.

 

If your MA-1 DAC doesn't use the USB power from the PC, I think this cable might be a good idea to try before the Jameco purchase: Acoustic Revive USB Cable USB1.0SP 1m Independent Power Signal Line Separate A | eBay. Yes I know this Japanese cable is very expensive but it's very easy to make your own as well (just buy two cheap USB cables and one USB A head connects power lines and the other A head connects the signal lines). My DAC doesn't use the USB power from the PC; I'm gonna make such a cable soon.

 

No offense but I've already posted that:

1) the MA-1 absolutely needs 5V USB power from the computer (hence my posts)

2) and that I have tried numerous USB cables including the Acoustic Revives (both dual conduit and single). My fave is still the Wireworld Platinum, but liked the AR Sp and the dual conduit RAL (although Brad is redesigning).

 

The Jameco I have is 6vDC500mA and the correct plug size and tip polarity...but the card needs 6.5vDC at least.

 

Jesus is hesitant to recommend any power supply he hasn't seen, of course, but is checking with SotM on the specs, regardless.

 

(This is continuing to hijack wayyy away from OP's ifi needs. Argh! Maybe a new thread is needed)

[jtwrace]

No offense but I've already posted that:

1) the MA-1 absolutely needs 5V USB power from the computer (hence my posts)

2) and that I have tried numerous USB cables including the Acoustic Revives (both dual conduit and single). My fave is still the Wireworld Platinum, but liked the AR Sp and the dual conduit RAL (although Brad is redesigning).

I really like the DH Labs USB cable.

[tubesound]

No offense but I've already posted that:

1) the MA-1 absolutely needs 5V USB power from the computer (hence my posts)

2) and that I have tried numerous USB cables including the Acoustic Revives (both dual conduit and single). My fave is still the Wireworld Platinum, but liked the AR Sp and the dual conduit RAL (although Brad is redesigning).

 

In this case, I think ifi is worth a try and you may use the Hynes for some other duties or even sell it. AMR claims ifi iUSB power supply has a lower noise than battery; that's a WOW.

[dallasjustice]

I see the 9v DC input on the device, but i don't see the PSU. Is this a BYOPSU device or does it come with one?