Noise with Computers, USB DACs, and Powerline Ethernet Kits

[rguenther]

Thanks for your quick response.
No, the noise is present as long as the laptop sits right beside it. Whether the laptop is battery powered or plugged into power doesn't affect the crackling.

[Paul Birkeland]

If you turn the laptop to airplane mode, does the noise go away?

[rguenther]

Yes it does!

[Paul Birkeland]

I would recommend purchasing a 0.1uF X7R capacitor (leaded, not a surface mount/smt).  Solder that between the ground shell of the red RCA jack and terminal 22.  That may or may not solve the problem, but it's a cheap experiment to try.

[rguenther]

Assuming I got the right part: it didn't solve the noise.

Now, with the Crack sitting besides the non-airplane-mode laptop,
a) when no RCA jacks are plugged in: audible hum on both channels, increases when volume is turned up. Masks the initial left channel crackling.
b) with RCA jacks plugged in (either to a cellphone or another grounded DAC): the audible hum mentioned above is gone - but the left channel crackling remains

The good news is: just 50-60cm of distance between laptop and Crack will reduce the left-channel-crackle to almost nothing. I'll just re-arrange my setup and take the capacitator out again :-)



PS I can't seem to insert the attached image. The capacitator reading is 104KH 250VMY. It's attached to terminal 22 and the ground lug of the red RCA jack.

[Paul Birkeland]

That is not an X7R cap, and yes, it may indeed matter.

[JoshuaA]

I just wanted to chime in that:

• Crack baseline: All sorts of CPU noise from ground loop from my DAC (SMSL D300) clearly audible at around 30-40% on the volume knob. Unplugging USB cable from DAC would remove all noise.
• Crack + Speedball: Would hear the same CPU noise at ~20% volume. Was driving me nuts!
• Crack + Speedball + anti-phase STTH2R06: Same CPU noise barely audible at 100% volume.
  

Given that I listen at 15-25% (depending on album), I'm very happy to report that thanks to the mod, I am listening to pure silence in between tracks and silent moments!

Thanks for making this a sticky, and the easy $1.24 + 5 minute fix!

[dittopizza]

Worked perfectly on my Crackatwoa!

I have an Audiolab M-Dac connected to my PC via USB and prior to this, there was noise leak at 0% volume (could still hear music), an audible background noise past 75% volume and moving my mouse on the screen caused background noise as well.

Now 0% volume silences all sound, volume knob turned to 100% has no background noise, and no more background noises with my mouse.

Was getting ready to replace my DAC prior to finding this fix.

Paid $2.02 at Digikey for two STTH2R06.

Thank you!