USB Signal Filters

What does everybody think about USB signal filters (iFi iPurifier3, Audioquest Shutterbug, Wyred 4 Sound Recovery, Ideon Absolute Time, etc.)? Are they worth the money? I understand that it would depend on the setup, but does anyone have specific experiences that suggest yes/no?

First of, let me point you to this excellent read:


USB (just like magnets) are surrounded by this “magic” (which is just engineering/science in my eyes).
So while you can have parasidic noise on the USB power, ANY device that relies on that power being clean should bring its own filtering.

There are proper power filters/conditioners for low voltage (example below), there are USB isolators (mostly for lab/industrial use when probing high voltage equipment) those cost a lot Example


Audiophile USB-stuff

This here is a Audioquest Jitterbug without the case:

There are two inductors, a diode (why?) and 3 capacitors in paralel with a high resistance resistor. Total parts cost is less than 3€ (with a nice PCB, maybe 6 when building only 100).
Those inductors (= chokes) filter some noise. For a proper filtering on the power rails, you want what is called “common mode choke”.

Working principle:

And here are some common mode chokes in the palmer purifier (blue arrows):

The Wyred Recovery lacks filtering completly (not even any meaningful capacitors in place):
image

The Ideon 3R Master Time


That is one hell of a big powersupply (why? Going to charge your tablet of it?). The torroidal transformer provides filtering against grid noise. Has a nice bunch of capacitors in there.

Could not find any pictures of the iFi dongle, so if anyone here owns one and can provide me with some pictures of the insides :wink:


There are noisy USB power sources. There is equipment that does not bring its own filtering to the table. So there is a valid reason to plug stuff into a powered USB hub or use a filter on the power. Leave the data alone!

Someone in China figured out how to do this:
image
Capacitors accross the power and Gnd rail, common mode choke and an LED with appropriate resistor to show the device has power. Costs $8 shipped.


Want some solder practice?

Digikey parts:


Edit: Messed up, one of those Mini-B breakout boards needs to be a USB-A socket. Or get a cable like this

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I just took delivery of the iFi iPurifier3 last week and it really does make a difference in the overall “depth” of the soundstage. Having spent 0ver 44 years as a working drummer in both live and recording sessions, I have a keen sense on what sounds good, ok and accurate when it comes to audio playback. I’ve also worked as a live sound mixing engineer and spent over eight years in the US Navy’s advanced electronics program (Polaris Electronics) so I know how things work.
The iFi is connected to my HP desktop PC running WIN10 and it provides access to my Hi-Resolution FLAC music library on a remote 4TB file server. The other end of the iPurifier3 is connected to an iFi Zen DAC which outputs to a set of Hifiman HE-400i Planer Headphones. All things considered, I believe that the clarity of the signal is the biggest contributor to sonic excellence. Sometime we forget that digital signals, being DC in nature, carry a lot of “hash”, cheap cables induce RF noise and some master clock timing pulses tend to drift so re-clocking is very important to eliminate jitter between the sender and the receiver. All told, I think that USB signal purifiers tend to be a worthwhile investment and in the case of the iFi product, its and economical investment.

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Welcome to the forum @USATRAN .

I agree with you, the USB signal path can have lots of issues. Schiit have tried to address that internally with their Unison technology. Even though my Bifrost 2 has Unison, I did experiment with a USB cable that isolated the power wires from the data-carrying wires and was amazed that there was a difference in sound quality. Just like you, I found a clear increase in soundstage.

Many would argue that we should be using a better connection like AES or Coax instead of spending money trying to improve something that is as flawed as USB, but I like to experiment with this kind of stuff because it’s interesting.

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I like the idea of better and more rigid connections for digital transfer. At the very least, there is a need to enable cleaner, jitter-free transfer means that also offers better shielding against RFI (given the amount of low-grade consumer electronics that almost every home is filled with) especially in urbanized areas. AES is good start as is cannon/amphenol-type connectors. My big concern is in order to get to a generalized use of heavier-grade digital connections, I don’t want to see cable and connector costs climb up into the stratosphere since most folks consider such connections esoteric. Quality Hi-Fi is sometimes taken for granted since the “bar” is usually set so low.

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