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Tips on interference noise on USB line
Tips on interference noise on USB line
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Old 6th April 2018, 02:23 PM   #1
skuliaxe is offline skuliaxe  Sweden
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Default [Solved] Tips on interference noise on USB line

Hi,

I recently built a speaker that works very well when using a laptop power adapter and USB power adapter separately. But I'm having interference noise when these two are combined.

When working without any unwanted noise: I have this power adapter connected to the AMP and separately I have a standard 5V 2amp USB power adapter powering a Google Chromecast Audio that is connected via audio jack cable to the speaker. Little to no noise or hiss at any volume.

However, when I use the same power adapter and also use the 5v 2amp USB built into the adapter then I get a very bad and loud interference noise even with volume at minimum. Here is a recording of the noise:
Vocaroo | Voice message

I was hoping to use the power adapter to power the AMP + Chromecast audio in order to reduse to 1 wall socket and better cable management.

Does anyone have any suggestions?

The wall socket is a "Type C" (all of them in the apartment are the same type) and I assume not grounded. Could this be the issue?

Last edited by skuliaxe; 14th May 2018 at 11:06 AM.
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Old 6th April 2018, 07:22 PM   #2
phofman is offline phofman  Czech Republic
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Please can you re-explain the way your adapters are used? I do not understand your description, sorry.
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Old 6th April 2018, 08:47 PM   #3
skuliaxe is offline skuliaxe  Sweden
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Hi.

I've attached a mock-up picture to try and explain.

The picture shows the connection when the interruption noise is caused. That is when the Power adapter is powering both the 19V to AMP and 5V to USB. This causes very bad interruption noise.

When I use a separate adapter for the 5V (regular mobile charger) then there are no noise issues.
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Old 6th April 2018, 08:59 PM   #4
Jerms is offline Jerms  United Kingdom
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You will need a GLI between the CCA and the amp.

I got this one that works fine.
QTX 201.087UK 3.5 mm Jack Ground Loop Isolator: Amazon.co.uk: Musical Instruments

But then switched to powering the CCA with this instead.
Yeeco Car Isolated Voltage Regulator DC DC Buck Converter 36V 48V to 5V 2A 10W Step-down Volt Transformer Stabilizer Module Vehicle Power Supply Switch Inverter Board with LED Indicator: Amazon.co.uk: Lighting

J.
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Old 6th April 2018, 09:08 PM   #5
Pano is offline Pano  United States
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Tips on interference noise on USB line
I don't see how there would be a ground loop problem using the same power supply. But maybe something is strange inside the power supply. Do you get that some noise if you use the combined USB to power the Chromecast into something else? Just wondering if the USB supply is dirty.

If you can lift the ground on the signal, that is worth a try. Beware loud noises!
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Old 6th April 2018, 09:21 PM   #6
phofman is offline phofman  Czech Republic
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My 2 cents you are hitting the very same ground loop issue I did in Adding an Amp into Thin-Client PC - the ground at chromecast audio output carries ground noise generated in ground lines by currents within the chromecast linux computer, making ground loop PSU - USB output - chromecast usb power input - (noise on chromecast ground lines) - chromecast audio jack sleeve - amp input - amp power jack - PSU jack - PSU.
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Old 14th May 2018, 11:05 AM   #7
skuliaxe is offline skuliaxe  Sweden
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Thank you all for the feedback.

I ended on purchasing this ground loop isolator from Amazon and it solved my problem:
Ground Loop Noise Isolator
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Old 20th May 2018, 06:08 AM   #8
wwenze is offline wwenze  Singapore
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Quote:
Originally Posted by Pano View Post
I don't see how there would be a ground loop problem using the same power supply. But maybe something is strange inside the power supply. Do you get that some noise if you use the combined USB to power the Chromecast into something else? Just wondering if the USB supply is dirty.

If you can lift the ground on the signal, that is worth a try. Beware loud noises!
Man, I have a ground loop problem between two sound cards on the same motherboard.
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Old 20th May 2018, 08:43 AM   #9
phofman is offline phofman  Czech Republic
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Apparently the motherboard ground traces between the two soundcards carry high currents produced by other components. Did you try inserting the add-on soundcard to another slot?
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