Help with Interference issue [resolved]

[Loquah]

Well today I bought a Schiit BiFrost, and low and behold, with USB, the same noise. So it's not the Dac causing the problem. How do I work out if there is a ground loop on the Crack, or on my PC, or somewhere else?

Hopefully others will chime in and help here, but I think the issue is in your power supply to the computer and or the USB signal from the computer.

Can you try plugging the DAC and Crack and PC into the same power board and report on the results?

[networkn]

Hopefully others will chime in and help here, but I think the issue is in your power supply to the computer and or the USB signal from the computer.

Can you try plugging the DAC and Crack and PC into the same power board and report on the results?

I'll try this tomorrow as I got my new Bi-Frost and I am in Musical Bliss right now

Not sure if this helps, but plugging into the BiFrost from the the SPDIF also has a slight buzzing noise in the right hand ear. Sadly the base for my crack isn't assembled so moving it, is no easy feat.

[Paul Joppa]

Just a note - ground currents (often called "ground loops") do not occur within a component, but rather between components. That's why they are so hard to trace ...  :^)

What happens is there is an AC current in the ground side of the interconnect, and that current drops a tiny voltage because the ground wire has some resistance, and that voltage gets added to the signal.

You can start with the Crack no connected to anything, and the volume turned all the way down. If there is hum, it is within the Crack. (You can then turn the volume up, and detect whether there is electromagnetic interference noise - always good to eliminate other possible problems!)

Then connect the DAC to the Crack, with nothing else connected to the DAC. If you get a new hum/noise then the DAC is likely introducing a noise current into the interconnect ground wire. If the DAC has a two-prong plug you can try reversing it, sometimes this helps. You can also try running the power cables close together for as long a distance as possible, sometimes that helps.

If there is still no noise with the DAC connected to Crack, then connect the computer. The same comments as the above paragraph apply. The computer is likely connected to other line-powered devices such as a router or a printer, so you can try disconnecting them to further isolate the problem.

[networkn]

Just a note - ground currents (often called "ground loops") do not occur within a component, but rather between components. That's why they are so hard to trace ...  :^)

What happens is there is an AC current in the ground side of the interconnect, and that current drops a tiny voltage because the ground wire has some resistance, and that voltage gets added to the signal.

You can start with the Crack no connected to anything, and the volume turned all the way down. If there is hum, it is within the Crack. (You can then turn the volume up, and detect whether there is electromagnetic interference noise - always good to eliminate other possible problems!)

Then connect the DAC to the Crack, with nothing else connected to the DAC. If you get a new hum/noise then the DAC is likely introducing a noise current into the interconnect ground wire. If the DAC has a two-prong plug you can try reversing it, sometimes this helps. You can also try running the power cables close together for as long a distance as possible, sometimes that helps.

If there is still no noise with the DAC connected to Crack, then connect the computer. The same comments as the above paragraph apply. The computer is likely connected to other line-powered devices such as a router or a printer, so you can try disconnecting them to further isolate the problem.

Hi Paul

These are the facts as I understand them right now.

1) Amp with nothing connected - No unusual noise
2) DAC connected to Crack, but no USB Connected - No unusual noise
3) ODAC connected to USB on Desktop Computer, connected to Crack - Noisy
4) Bifrost connected to USB on Desktop, Connected to Crack - Noisy
5) ODAC/BiFrost Connected to Laptop via USB - No Noise
6) ODAC to Headphones directly, connected to PC or Laptop via USB - no Noise
7) BiFrost Connected via SPDIF to Crack - Slight noise - Not as bad as via USB
ODAC connected to PC via USB then Connected to O2 AMP - No Noise
9) ODAC Connected to Laptop via USB then Connected to O2 Amp - No Noise
10) Noise from 3 doesn't seem to change as I adjust the volume knob on the crack
11) Noise from 3 doesn't seem to change if I remove one of the RCA's or the other, or if I swap them around
12) Noise from 3 not affected by type of music playing, or sample rate etc.
13) Noise from 3 can be drowned out if the volume is loud enough (Music
14) The Music coming from the crack in 3 sounds Excellent, just the buzz in the background
15) Noise from 3 moves from right hand to left hand depending on how far the headphone is inserted into the jack.

I have tried to troubleshoot this as methodically as I can...

[Paul Joppa]

Excellent data!

I'm going out of town so hopefully PB will pick up this thread, but you have pretty much confirmed (as I see it) that the noise comes from a ground current running from the desktop computer to the Crack ground, which is connected to the power line safety ground. (I assume the O2 has a two-prong power cord and is double insulated instead of being safety grounded.)

If I am right and you can use an optical interconnect to the DAC, that should solve it. That would break the ground current path.

[Paul Birkeland]

Yeah, this kind of thing isn't all that uncommon.  You could also try a powered USB cable, though that may or may not solve your issue.

The optical connection is a very good option.

[JamieMcC]

Sound similar to my experiences rerouting of cables and switching to optical interconnect for dac and pc sorted it out.
The hardest noise to trace was a intermittent buzz during the winter in the evenings it was driving me nuts coming and going and turned out to be a electric oil filled radiator in another room tripping in and out on its thermostat. I was running my internet signal through the houses power sockets at the time.

[networkn]

Ok Additional things I have tried today without any luck:

1) Put the Crack Amp, PC and Dac into the same powerboard. - Noisy
2) Unplugged al PC peripherals, Keyboards, mice, other USB devices (basically nothing except power and Coax SPDIF) - Noisy
3) Switched from SPDIF to Coax Spdif - Noisy
4) Unplugged everythng except headphones and power and turned the volume right up. It's Silent other than some very temporary noise in some parts of the turn, until I am 80% round where I then hear a faint hum

I can't run a powered USB as I don't have one, but given the bifrost is AC powered, and the same thing happens with it, I am inclined to think it wouldn't help.

Is there something I can do with a multimeter to test the crack for a ground loop?

[Loquah]

Ok Additional things I have tried today without any luck:

1) Put the Crack Amp, PC and Dac into the same powerboard. - Noisy
2) Unplugged al PC peripherals, Keyboards, mice, other USB devices (basically nothing except power and Coax SPDIF) - Noisy
3) Switched from SPDIF to Coax Spdif - Noisy
4) Unplugged everythng except headphones and power and turned the volume right up. It's Silent other than some very temporary noise in some parts of the turn, until I am 80% round where I then hear a faint hum

I can't run a powered USB as I don't have one, but given the bifrost is AC powered, and the same thing happens with it, I am inclined to think it wouldn't help.

Is there something I can do with a multimeter to test the crack for a ground loop?

No (to ground loop testing), because there isn't one in the Crack or you would hear noise even with nothing plugged in. The issue you have is occurring outside of your Crack and being transmitted into the Crack via the source devices you're using (i.e. PC to DAC is where the noise is generated).

Can you use optical or is that noisy too (or not available)?

I know some people have tried removing certain power-related pins from USB cables with some success on this type of issue, but I don't know which ones or if it would work for you here. Perhaps someone can elaborate.

[Doc B.]

You could try a cheater plug on the PC. A person might be inclined to try a cheater plug on the Crack, but of course as the manufacturer I have to discourage that as it defeats the safety ground in our product.

[NightFlight]

Just my 2 cents here...

Don't defeat the safety ground on the crack. Even if it were to fix the issue. Crack -> You -> Ground  = bad place to be.  Better to fix the ground issues elsewhere.

[networkn]

You could try a cheater plug on the PC. A person might be inclined to try a cheater plug on the Crack, but of course as the manufacturer I have to discourage that as it defeats the safety ground in our product.

When someone said that ground loop occurs between components, did they mean between two electronic components such as resistors and diodes, or between components being DAC and AMP or PC and DAC?

Given I have tried SPDIF and SPDIF Coax and the problem still exists, I am pulling my hair out.

If I use the headphone jack (6.25) on my Soundcard I can't hear anything and if I use my USB Headset into the PC, I can't hear anything. Unsure if this is useful information.

Is it possible the house itself isn't grounded and is it worth at this stage considering a electrician come to the house?

Any other troubleshooting steps? The PC is pretty huge so moving it isn't really that practical, and the only other PC's are laptops. I could take my Crack and Dac to work and see if it's still a problem, but I imagine it's within my house.

[networkn]

One thing I wanted to note though I warn up front it COULD be a Red Herring..

I have a pair of RS170 Headphones, Wireless, made by sennhiesser and I have long had an issue with a hum in those, whenever sound wasn't playing. So when I watch TV, plugged into the Headphone Jack of the TV, whenever speech or music isn't play, say between scenes or if there is a long pause in conversation the hum/buzz appears, but goes away when speech/music resumes.

[Paul Joppa]

When someone said that ground loop occurs between components, did they mean between two electronic components such as resistors and diodes, or between components being DAC and AMP or PC and DAC?...

I said that, and I meant there was a noise current in the ground wire of the interconnect between two devices - specifically, with all the great information you have obtained, everything points to a current in the ground ware of anything that connects between the computer and anything else that is safety grounded.

When I say "safety grounded" I mean that the chassis and the signal ground are connected to the third pin of the power socket.

It's sooo hard to be clear with just words! Sorry for the lack of clarity. Computer power supplies are notorious for being noisy in several ways, this is just one of them. I think the computer power supply produces an output whose ground side is not bonded tightly (i.e. with low resistance) to the signal reference ground used for SPDIF, headphones, USB, or other outputs.

When you connect something that is not itself grounded to safety ground, that "something" has a ground which fluctuates with the computer ground. You listen to the difference between the "ground" and the "signal" which both fluctuate the same way and there is no apparent hum. It's only when the Crack or another safety-grounded device provide a path for that fluctuating voltage to generate a current (into the safety ground) whic causes the non-zero resistance of the interconnect to acquire some noise.

If you can get the digits to the DAC without a ground wire, there will be no current and no noise. That's why I suggested an optical link, but wifi or bluetooth would do the same. Failing that, a transformer between the DAC and the Crack is a traditional solution; the two windings are connected magnetically but not electrically. Unfortunately it can be expensive to get good transformers. At one time Radio Shack sold some inexpensive audio transformers to solve the same kind of problem in car audio installations, they were cheap but they were cheap if you get my drift.

[Loquah]

If you can get the digits to the DAC without a ground wire, there will be no current and no noise.

Paul, is this why some people suggest removing the power-related pins from the USB cable if the DAC is self-powered or is the noise carried in the digital audio signal itself?