Noise. USB (and other)

[Wombat]

There seem to be a number of members experiencing issues with noise when using USB connections with their digital products.

Here are some interesting links related to the matter:

https://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf

https://www.murata.com/~/media/webr...atalog/products/emc/emifil/c33e.ashx?la=en-us

and FWIW: http://archimago.blogspot.com.au/2015/05/measurements-usb-hubs-and-8khz-phy.html

It is not a topic where replies to related questions can necessarily be reduced to forum reply simplicity because of the number of possible causes.
Good product design, proper house wiring and correct interconnection practises should prevent most issues.

 

[trl]

I did some measurements myself, here are only a small part of them: http://archimago.blogspot.com/2018/05/measurements-computer-usb-5v-power.html.

I concluded that:
- some computers are having cleaner or dirtier USB output power, perhaps the ground too
- no vacuum cleaner and no electronic appliances should run in house when listening to the music
- a dedicated grounding for the audio room could help (might be against country regulations!)
- Hum-X or similar devices that correctly lift the ground are indeed helping (don't just lift the ground, use a Hum-X that has powerful diodes inside!)
- isolation transformers are helping a bit, especially if ground can be safely lifted (with Hum-X or similar devices)
- playing audio from an pure sine-wave online UPS might help, especially if ground is lifted safely
- EMI/RFI filters are not very helpful, unless your mains power is really dirty
- not sure about the power conditioner...never tested, but I would honestly consider them overprices...in general (I would pay for an true online UPS with fulle sinewave instead)
- sometimes none of the above are necessary, audio just plays perfectly, no mains hum and strange noise can be heard
- sometimes none of the above really help (there can be mains hum, I've heard radio waves with sensitive cans having longer cables etc.)