Noise with Computers, USB DACs, and Powerline Ethernet Kits

[Deke609]

They are 25 freaking dollars each if you buy 50 at a time!

Neat idea though.  And if they actually work for breaking ground loops, they might be worth it for a lot of people.

One could also just install a tiny inductor between the earth ground and chassis ground, but I can't find a high current rated one on Mouser. These are all a lot cheaper than the Schurter thingy, but none are rated for much more than 5A, and most for a lot less: http://www.mouser.com/Passive-Components/Inductors-Chokes-Coils/Fixed-Inductors/_/N-wpczZ1yzvvqx?P=1z0z819Z1z0z7l5Z1z0wohhZ1yzjx1iZ1z0wqhyZ1z0jky5Z1z0wqh6Z1yzjx12Z1z0wognZ1z0wqobZ1z0wqgxZ1yyt8gaZ1z0wqhwZ1yztq3uZ1yyt8f1Z1z0woglZ1z0wqo9Z1yzmpecZ1z0wkc2Z1z0j7djZ1z0wqhsZ1yxadcvZ1z0j5rrZ1z0wogjZ1z0wqo1Z1yztpvpZ1yi47jgZ1z0wkc1Z1z0wqhqZ1z0jkw7Z1yu90k7Z1yzuwe3Z1z0woghZ1z0wqo0Z1z0woh9Z1yvgg2oZ1yzuvkkZ1z0wqhoZ1yzakszZ1yxh8woZ1yy85mjZ1y9gfh8Z1z0wogfZ1z0wqppZ1z0wpgmZ1yu90l4Z1z0wfhjZ1z0wqhnZ1yzuvk8Z1yy7e5iZ1z0wqn1Z1yzsc00&Keyword=inductor&FS=True

I'm not sure if that would pass electrical code requirements.  I'm guessing one probably needs a current rating on the ground connection that is at minimum the same current rating as the breaker at the panel (e.g., 15A or 20A).

cheers, Derek

 

[Paul Birkeland]

I would bet that those would pass 20A and pop a circuit breaker pretty easily. 

 

[Deke609]

Fair point - it only needs to handle the current for a split second.

 

[Paul Birkeland]

Still, I don't think these would get the desired result.  For audible noise, these would be a dead short (it's a piece of wire after all) and would only present significant impedance to high frequency noise that wouldn't otherwise be audible, and that we would otherwise want to shunt to earth as effectively as possible.

 

[Deke609]

Yeah, that makes sense. they'd only be appreciably reactive in the MHz range.  The application example diagram in the Schurter datasheet shows them used with a mainframe computer and peripherals.

 

[DanceTomato]

I would absolutely not use surface mount diodes in this application.

Order 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006, 1N4007, UF4001/2/3/4/5/6/7.

Thank you Paul B, I have ordered some 1N4007 (1A/1200V) following your advice.

 

[cddc]

The maximum peak signal voltage you could send into a Crack with the volume control all the way up is 1.5V.  If you have 500mV peak of noise current because of a polluted ground, that's not a small voltage at all!

If I understand the paragraph correctly, the noise current is coming from the ground pin in your power outlet / power strip, and the pair of twisted diodes is to block the noise current from entering the Crack, am I correct?

 

[mcandmar]

They are 25 freaking dollars each if you buy 50 at a time!

~$5 from Mouser.  Will add one to my next order and measure them against the 10r/.1uf trap i am using in my pre amp.

https://www.mouser.ie/ProductDetail/Schurter/DEHL-10-0001/?qs=%2Fha2pyFaduglz%2FafWzmtwPY7x75HshQWsFSrhm4Ey1uJ9e%252BfusRydw%3D%3D

 

[Paul Joppa]

If I understand the paragraph correctly, the noise current is coming from the ground pin in your power outlet / power strip, and the pair of twisted diodes is to block the noise current from entering the Crack, am I correct?

Usually, what we call "ground loop" hum/buzz comes from capacitive coupling from the power transformer primary winding to the signal amp power supply secondary (the high voltage in tube amps). The capacitance is small, on the order of 100pF,  so it presents a high impedance at power line frequencies and can be shorted to ground through a 10-ohm resistor.

The diodes are there in case there is a fault that presents a low-impedance source, such as a short from the power line to the signal ground. In normal use, they are not active and have no effect.

 

[cddc]

Usually, what we call "ground loop" hum/buzz comes from capacitive coupling from the power transformer primary winding to the signal amp power supply secondary (the high voltage in tube amps). The capacitance is small, on the order of 100pF,  so it presents a high impedance at power line frequencies and can be shorted to ground through a 10-ohm resistor.

The diodes are there in case there is a fault that presents a low-impedance source, such as a short from the power line to the signal ground. In normal use, they are not active and have no effect.

Thanks a lot for the explanation, PJ. I could hardly understand what you said, mainly due to my ignorance in electronics.

1.) so the capacitive coupling (first time to hear that coupling in the transformer  ) from the power transformer primary winding to the secondary windings will pass some small line current (110V 60Hz) to all secondary winding circuits (the 6.3 VAC heater circuit and the 2x0 VAC unrectified B+). But how the capacitive currents are grounded, I can't find any 10-ohm resistor in Crack?

2.) the twisted diodes are breaking the ground loop if I understood PB's 'ground breaker' correctly, so why they are not active and have no effect?

 

[Paul Birkeland]

There are some vintage components that just use a 10 ohm resistor instead of the antiphase diodes.  I prefer the diodes a bit because the peak current capabilities are better specified.

 

[cddc]

https://en.wikipedia.org/wiki/Ground_loop_(electricity)

The Ground loop (electricity) article on Wikipedia is terribly written, but I think I roughly got the idea of 'ground loop'.

So the RCA cables that connect Crack and DAC form a ground loop (ground of Crack -> Crack chassis -> RCA grounding wires -> DAC chassis -> ground of DAC -> ground of Crack), and the loop acts as a single-turn secondary winding of a transformer. So through induction it will generate some small noise current from ambient magnetic fields - magnetic fields that come from the main power line (60Hz), router, computer, etc.

So the 'ground breaker' diodes from PB will break the ground loop, preventing it from generating noise current thru induction. Am I correct?

 

[Paul Birkeland]

It's more about creating a break in the blue line in this image, and mostly breaking the line between the PC and the Crack.  What we don't want is for any nasties riding on the earth connection from the PC to travel through the signal cables, into the Crack, then to earth through the Crack.  A DAC which has its own power supply and does not rely on USB for power will tend to do this on its own.  We used to suggest using a DAC with an optical cable to do this, or SPDIF with a proper input transformer, but the antiphase diodes create an opening in the loop for far less money.

 

[cddc]

Thanks a lot, PB, for the image.

I think my understanding of 'ground loop' from the terribly written self-conflicting Wikipedia article is exactly the blue line loop in your image.

My computer and DAC both come with SPDIF. I once tried connecting them via an optical cable, but couldn't hear any difference vs the USB output to DAC.  :-[

Then I did some google search, and it seems some people think the SPDIF output from computers is not optimized for HiFi audio, they are designed for data transfer, so the jittering from SPDIF on computers will be very high due to poor clocking. Not too sure about these technical stuff  :-[

 

[cddc]

It just occurred to me that there is relatively easy solution for dealing with lots of shielding that needs wiring to ground: install your two-diode mod, but isolate the shielding from chassis ground and wire the shield drains directly to the earth ground lug of the iec inlet.

You can do that or move the diodes to between the audio ground and the chassis ground.

That's an even better idea! Thanks PB.

Just intrigued by the talk, but couldn't fully understand it... :-[

I can understand @Deke609's method to wire his Faraday shielding cage to the earth lug of the IEC power socket directly in order to bypass the diode 'ground breaker' and drain the EMI noises captured by the Faraday cage to the ground.

But I couldn't quite understand PB's approach. Where are the audio ground and chassis ground?

I just learned today that the Crack's "ground bus" is grounded thru the 3U/L tab, so should we break the grounding connection there and insert the "ground breaker" there?

 

[Paul Birkeland]

Sure, you can go ahead and isolate terminal 3 and install the antiphase diodes between terminal 3 and the chassis. 

 

[cddc]

Cool, thanks a lot for pointing out the "ground breaker" location for Cracks with Faraday cages, PB!

 

[Geebs]

Hi there - I'm a newbee for comments to the forum.  I built my BHC with Speedball last June; it works well until recently when I notice the following.

I notice/hear/feel a 'static electricity' type shock in the right channel of my new (2 mos) ZMF headphone.  It is winter, dry and lots of static all over my gear.  I rolled a new tube and thought it went away.  Rolled another one and it's still there.  Zach at ZMF has not experienced before.

Has anyone had this happen to them?  Would the fix that Paul started with this thread solve this?

Thanks - and if I'm doing anything wrong in the forum comments (style, quotes, etc.) let me know that as well.

 

[Paul Birkeland]

Is this noise present with nothing plugged into the RCA jacks on the Crack and the volume pot turned all the way down?

 

[Geebs]

Thanks Paul - I will try to replicate it under that condition.  I will also try another headphone/cable to see what the result might be.