S10 problem: Hum on the left channel > solutions?

I have an Up2Stream S10, which since recently produces a Hum on the left channel. For a complete picture: the S10 is connected to Line in of my amplifier, to get a streaming signal into the amplifier. The Hum typically sounds like a grounding problem.

What I did

  1. I opened the S10 casing and unmounted the PCB to have a visual look. Visually there’s nothing exceptional.
  2. I reflowed the solder on the mini-jack connector for the Aux Out. And while I was doing so, I also did the same for the other mini-jack connector for Aux In. Testing after the solder reflow, did not change anything. There is still a Hum.


  • Anyone who has had this too?
  • Any recommendations for a solution?

Hi Ernst,

There are not too many components between the internal DAC and the jack socket, a 10uf capacitor C35 and 0R resistor R18. You could apply some slight pressure on these with something non metallic to check if the joint is dry, but I wouldn’t think that this is the issue.

Have you tried an external DAC to see if the issue remains?

Thnx @Steve1 , good to hear you again!

I checked for the components you indicated. It looks a bit different with my S10, since this is a bit of an older version (see picture with the Linkplay board removed).
Anyhow the components are very small (SMD … ;- )

I think what I will do is the reflow trick that I did before with the video board of an Apple iMac: 10 minutes oven heating at 200c. For the iMac it did the trick.

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The reflow did not make a difference, but in the meantime I found out that the problem is either the amplifier behind the S10 or the cable connection.

Some additional testing showed this:

  • When I use a battery powered audio source device (e.g. iPod), there is no hum.
  • When the same device is powered by a USB wall plug, there is a strong Hum.

So I think there is a ground loop effect as soon as the audio source is powered via a wall outlet.
This also means the problem is NOT with the S10.

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@Steve1 @zpl1025 @anyone

New findings
Yesterday and today, I did some extra testing. Using different audio sources, like an iPod instead of the S10. But also different Power plugs.

At some point I noticed a huge difference in Hum when I connected an iPod and powered it with different USB wall outlet plugs. One of them gave almost no Hum, while another one gave a huge Hum.

Then I switched back to the S10 and its own USB wall outlet plug. Again this caused a big Hum.
Next I switched to the USB wall outlet plug that gave the least Hum with the iPod. This resulted in much less Hum, only a little hearable when being nearby the speaker.

My conclusion
The combination S10 and its own USB wall outlet plug, has the most Hum in this case, but caused by its own USB wall outlet plug.
Replacing it with a different USB wall outlet plug, will keep the Hum under control.
If anyone has the same problem, search for a USB wall outlet plug that has a low distortion to the audio signal.

My question
Since I am looking for NO distortion/Hum; who can recommend a USB wall outlet plug that creates NO distortion/Hum?

Hi Ernst,
I seem to remember that I recommended this one to you previously?
Quite expensive but very good I’m led to believe https://ifi-audio.com/products/ipowerx/

Thnx @Steve1

Yes, you are right, you mentioned this one before. And I know this company/products have a good reputation.
In my case the adapter is too big and priced a bit too high.

What I am going to try is to find an original Apple iPhone charger model A1400, 5V, 1A.
Some people mention that this one probably has the lowest distortion.

What maybe also has some influence is the USB-A to Micro B cable. I am not sure, but I can imagine if such cable is only wired for the power, that the distortion might also be less.
If there are USB-A to Micro C cables with only power wires inside, I don’t know.

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You could try a couple of clamp on ferrites on the cable?

I can now confirm the original Apple iPhone USB charger solved my issue. This charger / step-down converter does not cause any Hum. To be exact, there is a little Hum, but only hearable when the ear is within 20cm of the speaker driver.

Important notice: there are many USB chargers that claim to be Apple Original, but are not. Since Apple sometimes changes the design, it makes sense to check the Apple website for information on checking the originality. Mine looks like this and works:

Thanks @Steve1 for thinking with me and suggesting checks and solutions!