ifi iPurifier3 USB Filter Review

[Lambda]

What they won't measure are issues orthogonal to the device under test. Noise over USB ground will travel on the RCA output and potentially cause audible problems. Switch DACs is not going to help you except randomly.

If the DAC is designed badly.
if it has proper isolation Noise over USB ground will not travel to the RCA or XLR output

On the other hand if dose not has any "isolation" and Noise over USB ground Would travel to the RCA output it would also go to the XLR outputs.
In this Cases your only suppressing the noise by the CMRR of the reviving device.

This is why i say CMRR of the reviving device shuld be tested as well as it shuld be tested if/how mush Noise over USB ground Would travel to the RCA output.
Since Noise on the USB ground is normal.

 

[amirm]

if it has proper isolation Noise over USB ground will not travel to the RCA or XLR OUTPUT.

Major effort is put in high performance DACs to provide such noise isolation. With RCA you couple the two devices and subject yourself to ground loops regardless of what is going on with USB. Only XLR avoids this and with it obviate the need for USB ground isolation.

 

[Lambda]

Major effort is put in high performance DACs to provide such noise isolation

Not in all of them... this is why it would be nice to test this...

With RCA you couple the two devices and subject yourself to ground loops regardless of what is going on with USB. Only XLR avoids this and with it obviate the need for USB ground isolation.

With XLR you do the same thing...

The same ground loop common mode currents would go trough the XLR cable since they also connect ground of the reviving and transmitting device.

In this Cases your only suppressing the noise by the CMRR of the reviving device. This is why i say CMRR of the reviving device shuld be tested

Only XLR avoids this and with it obviate the need for USB ground isolation.

So XLR is not automatically obviate this its only suppressing the effect.

Beaus do to the differential signal of the XLR connection the common mode part can be partially rejected.
How good an how mush of it still depends on the CMRR of the of the reviving device. (and other things like DACs output impedance matching and symmetry)

Why and how shuld i trust the AMP to filter out the CM part of the signal that shuld not be coming from the DAC (USB) in the first place.

 

[amirm]

I am not going to chase non problems. You were supposed to provide tests to demonstrate these points some three years ago. You asked for two weeks yet here we are.

 

[Sokel]

The most common threads about noise for many years across the forums is strangely not about complex set ups and systems but the simple PC>DAC>active monitors.
Many times if not the most,with balanced connections.
And that 4-5 USB hi-speed chips found in most of the implementations usually works.

I don't know what this iFi contains,the new ones though do as they promise,up to any rate.

 

[Lambda]

I am not going to chase non problems.

You kind of do.
DACs are a solved problems for the scope of your tests.
You can get ~100€ device that is audible transparent (within the scope of your tests).

So i would say you chase non problems
And you ignore the ones that regularly come up here like:

Amir and others have repeatedly stated that a well-designed DAC will already filter power/be galvanically isolated, and devices like the Purifier and others are not necessary. Considering that the M500 MkIII received a glowing recommendation, it seems reasonable to assume that it too falls under the category of "well-designed DACs", but there seems to nonetheless still be potential for noise issues,

It might be not so common problem. but whats never a problem is okay DAC "sounding" bad.

 

[giov5]

I am not going to chase non problems. You were supposed to provide tests to demonstrate these points some three years ago. You asked for two weeks yet here we are.

I've also had the same problem as Ian, using a Topping D70 Pro and A70 Pro stack (Running short balanced cables), connected to a Desktop with an RTX 4090 GPU. I hear a ton of noise coming from the USB input at higher output levels. I have to turn the volume high enough on the A70 Pro to even hear it, which is not a problem with most music, etc... but for some content like movies, it's definitely a noticeable issue. The issue is worse if, for example, I scroll through a webpage, you can hear the noise from the GPU through the headphones very audibly and it seeps into lower volumes. I would not be surprised if it's also an issue with gaming. Flipping the "Ground Lift" switch on the A70 completely eliminates it, though that is not a common feature.

If I ever have time to record and test it and show it, I will.... but for other's I personally do not think it's true that all dacs deemed "audibly perfect" on this website actually are... I also own a bifrost 2 with its galvanically isolated USB input and it has no such issues. Maybe if you get a power cable and rip the ground pin off the end, that might work as well, but your amp will no longer be grounded.