IFi Defender +…the polish you need for dirty USB audio!

[Schlippwhip68]

I have an Lenovo M920q PC. This little 1 Litre box of wires ‘n’ bits is my primary music server. It’s quite a cost effective solution. It is not the most quite or cleanest motherboard made and many have noted this with the Lenovo PC. In short the USB on this thing is dirty, noisy also impossible to dumb the power down but that is another issue.

I run an usb cable to the Douk Audio U2 Pro (2025) and optical to the dac. I ran coaxial to the dac but static crackle soon killed that idea.

The sound was clean, not run home and tell your mum impressive, but clean enough. In consideration of nullifying the static via the coaxial connection from the U2 to the dac I decided to grab an iFi defender + when I saw one at a very reasonable price. I had no idea what this thing would do realtime and only had theory based on what it supposed to do.

The iFi Defender arrived today and after some fiddling around got the thing pushed into place and the U2 Pro plugged in. I am using a cheap GaN 5v power supply from Amazon to power the Defender.

Everything a place and into Apple Music to pay a few select tracks with desired frequency highlights.

What a difference!

Big clean up operation complete and in one little device! Just how dirty the usb power delivery straight from the PC to the U2 is now clearly evident by just how effective the iFi Defender + performs. It cuts off the power from the usb that was feeding the U2 Pro and with the power supply plugged into the Defender now feeds the U2 Pro with that power.

The difference is literal night and day. The bass is much cleaner and more precise without all that dirty noise coming from the motherboard. The vocals have lifelike clarity and the high etc and all clean, clean, clean!

This is a significant upgrade to any PC based system imo and not just for ground looping, hum etc but also just for dirty usb!

I would recommend this little gadget to anyone using a PC and usb as their audio source without any hesitation. I don’t work for ifi or am sponsored to say this. This is purely my own equipment and experience and I have to say iFi, top job boys and girls!

 

[staticV3]

FYI, a $5 Delock 83176 USB cable achieves the exact same thing.

Cut the red wire within the back cable sleeve and you get external power supply and no VBUS from the host:

 

[staticV3]

You can find similar cables for $1-2 on AliExpress: https://www.aliexpress.us/item/2251832665579348.html

Cut the red wire and they'll again perform identical to the iDefender.

 

[staticV3]

If you're after true galvanic isolation, then for the same price as the iDefender you can buy proper USB isolators like one of these:

Topping HS01
Topping HS02
Hifime High-Speed USB Isolator v2
JDS Synapse
Neutron HiFi Isolator V1
DSD TECH SH-G01L
Olimex USB-ISO-HS

NVarcher also sell one on AliExpress.

So yeah, identical functionality at a tenth of the price, or vastly superior functionality at the same price.

iFi's tweaks like the iDefender remain exceptionally poor value.

 

[RandomEar]

Just to clarify: Did you get any audible noise or hum from the U2 before adding the defender?

 

[IsaacOscar]

FYI, a $5 Delock 83176 USB cable achieves the exact same thing.

Cut the red wire within the back cable sleeve and you get external power supply and no VBUS from the host:
View attachment 511458

Hmm the description of it I found online says this (emphasis added):

Please note: This product is not for use with power delivery, only for data.
[...]
When plugged into the source device’s USB socket, the iDefender+ detects whether there is a ground loop problem.

It breaks the ground loop by ‘intelligently’ disconnecting the computer’s earth and, as well as eradicating audible ground-loop hum, it lowers the system noise floor, improving resolution and dynamic contrast.

So it seems it's doing more than just disconnecting the power? (You can also provide power through the side USB-C port). Seems very very expensive though for what seems like a simple task.

I wonder if someone's opened one up to see what is actually in it...

 

[Schlippwhip68]

If you're after true galvanic isolation, then for the same price as the iDefender you can buy proper USB isolators like one of these:

Topping HS01
Topping HS02
Hifime High-Speed USB Isolator v2
JDS Synapse
Neutron HiFi Isolator V1
DSD TECH SH-G01L
Olimex USB-ISO-HS

NVarcher also sell one on AliExpress.

So yeah, identical functionality at a tenth of the price, or vastly superior functionality at the same price.

iFi's tweaks like the iDefender remain exceptionally poor value.

Thanks for the info. I checked those recommendations out and they are a little more expensive, less compact too.

The iFi does an excellent job so I am happy to stick with it.

It’s probably old hat by now but with usb it does seems galvanic islolation is the ‘rub’ that does actually matter for actual genuine sound quality out of a PC.

 

[Schlippwhip68]

Hmm the description of it I found online says this (emphasis added):


So it seems it's doing more than just disconnecting the power? (You can also provide power through the side USB-C port). Seems very very expensive though for what seems like a simple task.

I wonder if someone's opened one up to see what is actually in it...

The reduction of the noise floor of my Lenovo M920q using the Defender is a corner turn in obvious. I don’t know what’s contained in this unit but sorry, I am not at liberty to open it up.

 

[fatoldgit]

FYI, a $5 Delock 83176 USB cable achieves the exact same thing.

Cut the red wire within the back cable sleeve and you get external power supply and no VBUS from the host:
View attachment 511458

quite rare this will work.

Many DAC power their USB receivers (or even the whole DAC) off the 5VDC and even when they don't (i.e. use internal power for USB receiver) they use the 5VDC to sense when a DAC is connected.

Cheap enough to try but big probability it won't work.

 

[voodooless]

This is the inside of the ifi iDefender Max. Doesn’t look like much…

 

[mhardy6647]

View attachment 511968
This is the inside of the ifi iDefender Max. Doesn’t look like much…

"Fully Discrete, Designer Circuitry"

I'm seein' six transistors and a smattering of passives. Not quite no there there, but close!

 

[Nutul]

I'm a bit confused... why use a DDC reclocker to a DAC via USB??? It's completely useless. And nonsense...

 

[Schlippwhip68]

I'm a bit confused... why use a DDC reclocker to a DAC via USB??? It's completely useless. And nonsense...

Nope. Thoroughly useful on my £350 zen One Signature and most dacs upto £700.

Differences are heard not imagined.

 

[Schlippwhip68]

View attachment 511968
This is the inside of the ifi iDefender Max. Doesn’t look like much…

…it dosent look like much….its 2026, most electronics don’t seem to look like much but the Defender is much appreciated in my PC.

I’m not sure how this would perform elsewhere but the PC is valid.

 

[RandomEar]

Nope. Thoroughly useful on my £350 zen One Signature and most dacs upto £700.

Differences are heard not imagined.

Unless you heard noise or hum before installing the Defender, there is no difference in sound. USB is a digital signal. It works or it doesn't.

Bit errors and such are extremely obvious defects. If you ever listened to portable CD players without a playback buffer or played a damaged audio file from the HDD/SSD, you will know this. Even excessive jitter via S/PDIF or USB will lead to drop outs far before any other audible change occurs.

 

[IsaacOscar]

Unless you heard noise or hum before installing the Defender, there is no difference in sound. USB is a digital signal. It works or it doesn't.

Right. But the defender doesn't claim to do anything to fix incorrect bits. Rather it's about preventing noise from travelling through the USB power lines and into your analog output.

Is such a thing possible? And how do you detect it?

 

[RandomEar]

Right. But the defender doesn't claim to do anything to fix incorrect bits. Rather it's about preventing noise from travelling through the USB power lines and into your analog output.

Is such a thing possible? And how do you detect it?

Noise or ground loops via USB are relatively common when using a PC as the source. At least as far as I have seen. You can simply hear it, as soon as the amp/active speaker is on even with no music playing. The noise also often changes if you load the CPU or GPU and sometimes even if you move your mouse. On DACs with a well designed grounding scheme it shouldn't make it to the amp, but sometimes it just does.

 

[IsaacOscar]

Noise or ground loops via USB are relatively common when using a PC as the source. At least as far as I have seen. You can simply hear it, as soon as the amp/active speaker is on even with no music playing. The noise also often changes if you load the CPU or GPU and sometimes even if you move your mouse. On DACs with a well designed grounding scheme it shouldn't make it to the amp, but sometimes it just does.

Thanks I've not used USB speakers, but 3.5mm ones often hiss as soon a I plug the cable in.
(I haven't noticed any such problems with headphones or earphones though).

So the general advice would be if you don't notice/hear a problem, then there isn't one?

 

[RandomEar]

So the general advice would be if you don't notice/hear a problem, then there isn't one?

Exactly.

 

[Roland68]

quite rare this will work.

Many DAC power their USB receivers (or even the whole DAC) off the 5VDC and even when they don't (i.e. use internal power for USB receiver) they use the 5VDC to sense when a DAC is connected.

Cheap enough to try but big probability it won't work.

This works perfectly and has been successfully tested on countless DACs.
For DACs with their own power supply, you only need to disconnect the positive supply voltage; the negative supply voltage is needed to detect the connection.
For a DAC that requires a 5V supply, the positive supply voltage from the host is also disconnected, and the DAC is powered with 5 volts via the Y-cable.

Small circuit boards that accomplish exactly this are also available on AliExpress.