USB power noise reduction

[SiW]

When plugged into the mains with a switching power supply plug it’s silent but when I power it from usb (only needs 5v and has a barrel jack) I get some hum. It’s a DYP au-d3-192 small DAC.

Got some average usb to barrel jack converter cables to try and saves a plug on the wall being used but now get hum

Have swapped over between the usb lead and mains lead and it’s definitely from the usb power supply.

Happens on both coax and toslink options to the DAC so not a grounding issue further up the line.

The usb hub is a 4 way charger and gives 2.1amp per connection.

Is it worth trying a ferrite bead on the usb lead or anything else I can try?

Cheers!

Simon

 

[amirm]

No, ferrite beads filter at frequencies above 1 Mhz. They won't have any effect at all at 60 Hz and harmonics thereof.

 

[SiW]

Thank you sir

Any other way to stop this or just keep on using the wall socket?

Simon

 

[gvl]

Just use the wall socket.

 

[sophie smith]

Just out of curiosity, will the dual USB cord, with split connectors, one for power and another for signal, help in this case?

 

[amirm]

Just out of curiosity, will the dual USB cord, with split connectors, one for power and another for signal, help in this case?

We had a report of it helping with a Topping D10. As I have noted, the whole system of using unbalanced RCA connectors invites these kinds of ground loops. Without instrumentation, it is hard to know what is the cause. Usually messing with how things are powered helps or removes the problem so sure, try it.

 

[SiW]

Just out of curiosity, will the dual USB cord, with split connectors, one for power and another for signal, help in this case?

Where can you get these sorts of cables?

Sounds interesting.

Simon

 

[Vincent Kars]

Where can you get these sorts of cables?

https://ifi-audio.com/products/gemini3-0/

 

[Jimmy]

They can be made or purchased, however most of the time using a cheap usb hub instead of plugging the audio devices directly solves the problem, for example I'm using this (I don't have the power adapter plugged in) :

https://www.hama.com/i/00078472/hama-usb-20-hub-14-with-power-supply-black-cardboard-box

But many cheap hubs should do ok, many of them perform some power filtering.

Another (probably better) choice is to buy a usb isolator, but cheap ones are only usb 1.1 (not tested by me) :

https://www.ebay.com/itm/1500V-USB-...sh=item1eea309dc1:g:lsoAAOSwXIhbmIc0&LH_BIN=1

Anyway I've always solved this problem (at least audibly) putting usb hubs in the middle.

 

[graz_lag]

Where can you get these sorts of cables?

Sounds interesting.

Simon

I bought mine on Amazon for $20 or so.
Pls. see here for my experience with this particular solution : https://www.audiosciencereview.com/...ts-of-chord-mojo-dac-and-amp.5120/post-114587

 

[SiW]

Thanks guys - have tried on one hub (from the usb charger) but will dig out some others I have in a box.

Suspect it’s the usb charger not being the best design so will also test some other wall warts.

Simon

 

[DWPress]

Here was my DIY solution for a split USB cable:
https://www.audiosciencereview.com/...asurements-of-topping-d10-dac.2470/post-90089

 

[SiW]

So tested this further - it’s a ground loop occurring between the DAC and the amp.

When I touch the amp case or the phono to jack plug cable plugs between the DAC and the amp it goes away!

Using the factory mains power supply there is no hum, but when I swap to the usb lead through a usb hub there is also no hum when I use a quality single usb wall wart.

But when using a mains power supply to the usb hub there is the hum and when I use the usb charger there is also a hum. The ground loop is there in these scenarios and is fixed by touching the amp or the cable.

So what’s special about the factory mains plug vs the usb hub mains plug?

Pics of my setup, ‘bad’ mains plug (with the Belkin label) and ‘good’ mains plug (see big ferrite on the cable).