Unwanted digital noise (Not the standard noise floor) from studio monitors - Page 1
Forum section: electronics / beginners

author: Vildhjarta
author_rank: Contributor
timestamp: November 25, 2019, 07:35:21 am
content: Hi!A few months ago i bought a pair of Yamaha HS7 studio monitors to use together with my desktop.I will list my gear first so that you can form a picture of the situation as you read.Tower:Cooler master Cosmos SE midi towerMotherboard:ASUS Z170-E Socket 1151Processor:Intel Core i7-6700K skylakeProcessor water cooler:Corsair hydro series H115iRAM:Crucial Ballistix Sport 16gbGFX:GTX1080 G1 gamingSSD:Samsung 850 EVOHDD:Seagate Desktop SSHDPSU:Corsair CX 600M 600WWifi:ASUS PCE-AC68 AC1900Fans:2x140mm in front, 1x280mm on top and 1x120mm in the backExternal soundcard:Tested with both Focusrite Scarlett 4i2 (USB powered) and Focusrite Saffire 26 pro (Separate power supply and firewire connection)Studio monitors:Yamaha HS7 active monitorsCables:Standard power cables with ferrite beads. All jacks and XLR cables are balanced. Firewire cable is a IEEE 1394 compliant one.Monitor:ASUS 24 inch LEDKeyboard and mouse:Corsair K55 and SteelSeries Rival 300SWhen i plugged them into my Focusrite Scarlett 4i2 sound card (USB powered) there was this constant buzzing noise, which was emphasized whenever i moved the mouse or did anything that demanded power from my desktop. I tried changing the power outlet configurations to all different permutations with wall outlets, power strips (with and without surge protector), but to no avail.I then tried to disconnect all the hardware on my machine except the processor and storage units, still no difference. I then checked that all the cables were properly shielded, although i haven't opened any of the components since my electronics skill isn't up to par. I have googled this for hours but nothing seems to work.The only thing i can imagine it being is some kind of resistance issue in the power cable for my PSU, which makes it easier for the ground to go through the firewire, out in my monitors and down through the power cables there.This is so frustrating, considering i have spent lots of money now on failed attempts, my recordings sound like crap (The buzzing affects my guitar pickups, so the closer i move to the machine the worse the sound gets) and it is impossible to use my monitors when playing games or such.If any of you have any ideas, or want to help out i would be really grateful!I will update this post continuously as i come up with more info, and take some pictures when i get home!Thanks!

author: iMo
author_rank: Super Contributor
timestamp: November 25, 2019, 11:25:10 am
content: How it works with your notebook?

author: Vildhjarta
author_rank: Contributor
timestamp: November 25, 2019, 11:36:28 am
content: I will see if i can get my hands on a laptop today! If the noise is absent on the laptop, what would you suggest the issue is?

author: magic
author_rank: Super Contributor
timestamp: November 25, 2019, 04:41:02 pm
content: Quote from: Vildhjarta on November 25, 2019, 07:35:21 amOh yeahQuote from: Vildhjarta on November 25, 2019, 07:35:21 amYep, that's the thing, usually. Even if your ATX ground cabling has 1mΩ of resistance, that's still 10mV of ground bounce when the CPU turns on and off and draws 10A of current from the 12V rail. If the speakers have their own Earth connection then they see the signal riding on top of that bounce and can't tell them apart.A cheap not-really-solution: load all CPU cores to 100%Do you have balanced inputs on those speakers?

author: Vildhjarta
author_rank: Contributor
timestamp: November 25, 2019, 04:45:40 pm
content: Yes, the outputs on both cards are balanced as well as the inputs on the monitors.I tried the setup with a Macbook now. No noise with nor without the charger connected.Do you think the high resistance resides in the PSU or in the power cable for the PSU?Thanks for the reply!

author: wraper
author_rank: Unknown
timestamp: November 25, 2019, 04:53:27 pm
content: Your sound card is crap if this happens. Did not utilize it being outside of PC and on external PSU. IMHO buy USB isolator or get rid of it and buy different sound card.

author: magic
author_rank: Super Contributor
timestamp: November 25, 2019, 04:58:51 pm
content: This is indeed something that shouldn't be happening with differential signalling, in theoryIs the noise still there when nothing is being played? Is it there if the cables are disconnected but there is ground connection between the PC and the monitors?Quote from: wraper on November 25, 2019, 04:53:27 pmWhich one?Without that bit of information OP might as well make a new career as a sound card reviewer.

author: Vildhjarta
author_rank: Contributor
timestamp: November 25, 2019, 05:02:15 pm
content: Quote from: magic on November 25, 2019, 04:58:51 pmThe noise is there from the moment i turn on the computer, and is severe if i enter the BIOS or start up games etc.I tried disconnecting the audio cables between the speakers and the sound card, and the noise vanished.As i mentioned as well, the buzzing is there even when the sound card is turned off (The Saffire 26 with its own power supply)

author: magic
author_rank: Super Contributor
timestamp: November 25, 2019, 05:15:00 pm
content: Quote from: Vildhjarta on November 25, 2019, 05:02:15 pmOkay, but what if you add ground connection then? Take some wire, stick the ends into the appropriate holes in the XLR. Or dunno, stick pins into the holes and touch them with the tips of a guitar cable, whatever. Or touch some other connectors with exposed ground, if available, if you are worried about damaging the XLR.It may be a star grounding fail in the soundcard, or it may be a star grounding fail in the monitors. If you get noise with only ground connection, you can be reasonably sure that changing soundcards won't fix anything. At this point it would be USB isolator or some weird trickery like manually converting USB to star grounding.

author: David Hess
author_rank: Super Contributor
timestamp: November 25, 2019, 10:36:04 pm
content: If the buzzing is at the line frequency or a harmonic, then it might be RFI from the input rectifier in the ATX power supply. A different power supply might fix this.But I agree with wraper, install a USB isolator between your computer and the USB sound device. USB is a real problem for audio because of its lack of galvanic isolation.

author: Bassman59
author_rank: Super Contributor
timestamp: November 25, 2019, 10:48:33 pm
content: Are the monitors plugged into a surge-suppressor power strip? If yes, how old is that power strip? Try replacing it. The MOVs in power strips get leaky with age and "hits," and that can cause all sorts of noise.Once upon a time, a friend and I were trying to track down a noise source in our rock club's PA system. Turns out that a power strip which had only Little-Lites plugged into it, was the culprit. That power strip was plugged into the same circuit as the console. With the power strip unplugged, silence. And yes, we unplugged the Little-Lites' wall warts first.

author: NOON Design
author_rank: Contributor
timestamp: November 26, 2019, 07:55:12 am
content: Some computers can have horrendous ground noise, for various reasons other people have speculated on. Your sound card is from a reputable manufacturer and is not likely at fault. You've likely got a ground loop happening.Professional balanced audio connections are designed to handle this kind of situation though. The 2 signal leads are referenced to each other rather than to ground, which is just a shield. You can safely lift the ground from one side of the cable. It will probably be quietest if you lift it at the sound card end so the shield is coming from the speakers back, but only trying it will tell. Cut or desolder the shield in the XLR or TRS connector and see if it makes a difference.

author: magic
author_rank: Super Contributor
timestamp: November 26, 2019, 08:50:50 am
content: This is a fine solution, but one caveat applies: if either end loses its earth connection through mains for whatever reason, things may go poof. It certainly is a danger with low voltage CMOS circuits and I'm not sure how resilient audio gear is.

author: EEVblog
author_rank: Unknown
timestamp: November 26, 2019, 09:34:14 am
content: Can you get the frequency of the buzzing noise?

author: Vildhjarta
author_rank: Contributor
timestamp: November 26, 2019, 05:05:03 pm
content: Thanks for all the replies!Quote from: David Hess on November 25, 2019, 10:36:04 pmThe new soundcard is firewire, still the same noise.Quote from: Bassman59 on November 25, 2019, 10:48:33 pmI have tried with many different power strips, and the surge suppressor strip is just a month old.Quote from: NOON Design on November 26, 2019, 07:55:12 amKind of embarassing since i am asking for help on an electronics forum, but i am not confident with my skills enough to go inside components (Ref. the post below by magic)Quote from: magic on November 26, 2019, 08:50:50 amQuote from: EEVblog on November 26, 2019, 09:34:14 amThere seems to be many layered on each other, but the most prominent one when i run games is around 1830-1850Hz.I will upload an audio clip. The first part of the audio is when i am ingame, and the last 5-6 seconds is just the "standard" noise with some mouse movement.

author: rsjsouza
author_rank: Super Contributor
timestamp: November 26, 2019, 06:09:43 pm
content: I used to have this issue as well, but it was with the built-in soundcard. Once I got one of those cheapie USB pendrive soundcards (Syba is the one I have) I could record dynamic microphones without problems.The USB isolator will help with conducted noise but it will be less effective for RFI. If you have a metallic box, you can try to shield your soundcard. Also, check what are the effects of touching a metallic part of your system. Sometimes you get different behaviours by touching different components.

author: magic
author_rank: Super Contributor
timestamp: November 26, 2019, 06:15:24 pm
content: I won't say it sounds exactly like my PC's ground bounce but it sounds similar. Anyone (who owns a desktop PC, heh) can produce such noise by connecting headphones between the motherboard ground and chassis. Or insert a jack cable into the audio input, press the tip at the other end against the chassis and record.You have 50Hz mains in Norway, right? So that 120Hz thing isn't from mains but some 7200RPM disk or whatever. Dunno, given that everything else is 900Hz and its harmonics I suspect it's ground bounce rather than RFI from the PSU. But ground noise really should be eliminated by balanced signalingFailure of safety ground is a rare occurrence, it has never happened to me yet. And if your mains wiring were faulty, there would be no ground loopSo it should be safe to try the ground lift at least temporarily to see if it makes a difference, even if I personally wouldn't make such installation permanent without adding some additional protection. You don't need to modify any equipment, only the cable. Use the lousiest and cheapest one you haveDo you have a DMM?

author: Vildhjarta
author_rank: Contributor
timestamp: November 26, 2019, 06:32:15 pm
content: Quote from: magic on November 26, 2019, 06:15:24 pmI tried once more to disconnect my SHDD which is running at 7200rpm, but still the same. :/Quote from: magic on November 26, 2019, 06:15:24 pmI'll buy an extra cable set that i can experiment with.Quote from: magic on November 26, 2019, 06:15:24 pmNo, definitely would come in handy now!

author: madires
author_rank: Super Contributor
timestamp: November 26, 2019, 06:59:02 pm
content: Another possible source of the buzzing is a SMPSU powering audio stuff. In that case proper filtering of the audio gear's DC power input helps (common and differential mode noise).

author: Bud
author_rank: Super Contributor
timestamp: November 26, 2019, 07:07:55 pm
content: USB power bus is full if crap. Connect an oscilloscope and see it for yourself. If you power your audio from USB you should change to a standalone power supply as the first step. Eliminate that noise source before doing anything else.

author: Vildhjarta
author_rank: Contributor
timestamp: November 26, 2019, 07:29:49 pm
content: Quote from: madires on November 26, 2019, 06:59:02 pmhttps://www.corsair.com/corsairmedia/sys_master/productcontent/corsair-psu-spec-table.pdfIf you search for CX600M. Can you get any clue from the specs?It seems to me as well that the issue comes from the PSU.Quote from: Bud on November 26, 2019, 07:07:55 pmThe sound card i use now has its own power supply, and uses a firewire connection to the PC.

author: magic
author_rank: Super Contributor
timestamp: November 26, 2019, 08:21:00 pm
content: Quote from: Vildhjarta on November 26, 2019, 06:32:15 pmI presume the mic picked this noise straight from the air, not through the speakers. No point testing such thingsQuote from: madires on November 26, 2019, 06:59:02 pmThat audio stuff is powered by a normal transformer. And, tangentially, it is indeed earthed to mains.https://www.head-fi.org/threads/yamaha-hs7-internals.745768/By the way, you could do the headphone trick I described. Maybe use some cheap headphones, though nothing bad should happen unless something is terribly wrong with the computer. If you hear the exact same noise that comes from the speakers, we can be quite reasonably sure that it truly is ground bounce that gets into the speakers. I think.And looking at those internal pictures really makes me curious what would happen if the ground of those speakers is connected to the PC's USB ground but there are no signal connections. You know what, it seems there are 1/4" jacks there in addition to XLR. So plug a jack cable in and plug any sort of USB cable into the PC. Take the USB plug at the other end and touch its metal part to the ground (sleeve) terminal on the audio jack. See if there is noise. BTW, if you touch any other terminal, there will surely be noise, and perhaps somewhat loud.

author: Vildhjarta
author_rank: Contributor
timestamp: November 26, 2019, 08:55:41 pm
content: I tried doing the jack vs USB cable experiment.And indeed, the noise was there, even worse.In this audio clip i first only have the tips touching, then i move the mouse, and lastly i drag windows around on my computer.

author: magic
author_rank: Super Contributor
timestamp: November 26, 2019, 09:41:27 pm
content: Hmm, I expected it to be exactly the same, not louder. Perhaps it's a matter of different resistance of the phono cable vs XLR. You are sure that you touched the ground part rather than some signal input?https://connector.pinoutguide.com/3_pin_stereo_plug/If that's confirmed then it seems that your monitors simply don't like ground currents flowing through them, simple as that, and the soundcards have nothing to do with it this time.And I suspected that this may be the case because it looks like the monitors have plenty of ground loops inside, between the various boards connected with cables and screwed to the metal chassis.That'sfor Yahama.Well, since this is balanced connection, you can disconnect ground in the analog cable, as others suggested. To protect equipment in the unlikely event that one side loses earth connection, a pair of diodes (one in each direction) could be wired between the two grounds where they are cut from each other. Diodes allow the two grounds to differ by a few mV, so the noise will almost certainly be stopped, but if one end becomes floating, they will ensure that this difference stays less than 1V. Maybe it's paranoia, but diodes cost peanuts so why not.And there is another possible solution, which may also reduce noise pickup by unbalanced soundcard inputs. That is to modify the USB cable such that it takes its ground from the PC's chassis rather than the motherboard. You would cut open the external isolation of the cable, cut the shielding braid, cut the black wire inside the cable and tie its end to some screw on the chassis. USB will probably tolerate this hack, and the soundcard will have undisturbed connection to earth, coming straight from mains through the PC chassis.

author: EEVblog
author_rank: Unknown
timestamp: November 27, 2019, 12:13:51 am
content: Quote from: magic on November 26, 2019, 09:41:27 pmGoogling shows similar reports from others, so yeah, maybe unforgiving Yamaha's.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 06:58:25 am
content: Quote from: magic on November 26, 2019, 09:41:27 pmThe noise came anywhere i touched the cable.Quote from: magic on November 26, 2019, 09:41:27 pmDoes this apply to firewire cables as well?The sound card i am using now is connected via firewire through a PCI-mounted firewire controller.Quote from: EEVblog on November 27, 2019, 12:13:51 amSo this suggests that my monitors are very susceptible to ground issues, and not suitable with systems that aren't optimized with "clean" signal management?I am considering buying myself a decent laptop now for studio recording, and reverting back to my old Bose Companions for the desktop machine.Do you think this will be a problem if i get a different set of studio monitors?

author: magic
author_rank: Super Contributor
timestamp: November 27, 2019, 08:44:31 am
content: Quote from: Vildhjarta on November 27, 2019, 06:58:25 amPerhaps one more check would be in order: touch the sleeve of the jack with USB and short the tip and ring together with some piece of metal. It should make no difference, or I'm an idiotQuote from: Vildhjarta on November 27, 2019, 06:58:25 amYes. The point is to isolate all audio gear from the noisy ground of the PC.Quote from: Vildhjarta on November 27, 2019, 06:58:25 amIt's lottery, both on the laptop and minotors front. Unless you can find somebody who reviews equipment and checks for this exact problem. Perhaps the situation is better in pro audio, but among "audiophiles" the standard solution seems to be randomly replacing components like a monkey until noise goes awayMore recently the smarter ones are buying USB isolators.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 09:07:36 am
content: Quote from: magic on November 27, 2019, 08:44:31 amWell, i tried the exact setup with a Macbook, and there was no noise.I just find it strange having to modify the components (None of the components are older than like 2 years) in order to make the stuff work, there has to be a simpler solution to this.I could try to change the PSU and processor, but i am leaning towards having a separate machine just for doing my music, and keeping the desktop as a gaming platform.Would be really cool to have one of you guys troubleshooting the gear IRL though, too bad i live up in cold Norway

author: magic
author_rank: Super Contributor
timestamp: November 27, 2019, 10:34:53 am
content: Quote from: Vildhjarta on November 27, 2019, 09:07:36 amWrite a letter to Santa or hire somebodyI do it for free to the extent that it's an opportunity to milk you for dataQuote from: Vildhjarta on November 27, 2019, 09:07:36 amThe problem is that audio designers have no clue how to deal with noise from computers and computer designers have no clue how to keep noise out of external devices. Exceptions may exist and sometimes even an ignorant designer will get it right, but that's it.I have a soundcard from a "pro audio" vendor which fails at star grounding. I have a laptop which literally makes noise from its internal speakers when I connect a USB device, they can't even keep filth out of their own circuitry in their own device.If you want a "simple" (by which it seems you mean "commercial") solution:1. Buy a USB isolator. Not sure if similar gadgets exist for FW.2. A CPU with half the power consumption will reduce noise by 6dB.3. Another few dB if you manage to find a PSU with substantially thicker cabling. Perhaps a bit to be gained from motherboard layout.Have fun throwing cash at it and experimenting.Laptops ought to be better even when plugged in because they run on less power. Apple may be OK because they are / used to be popular in the audio crowd so perhaps they care.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 11:12:26 am
content: Quote from: magic on November 27, 2019, 10:34:53 amI see, i think i might have an improper impression of the hardware available. I always thought that the big and known companies had these things sorted out when shipping their products, and that my case now was an exception, but if these setups usually need fine tuning and not just plug and play i suppose i should do some unorthodox procedures in order to remedy the issue.So, instead of the "okay, there is noise, something is wrong until it disappears completely" i should adopt the "okay, there is noise, optimize every component until it is as minimal as possible" regarding audio gear. The fact that it isn't on or off when it comes to interference, just various degrees of it.Luckily i enjoy learning new stuff and geeking out, just sucks a tad when the subject matter is my gateway for doing my biggest hobby.Should i get myself a DMM, or are there any other gadgets useful here?Thanks again to everybody who contribute here!

author: Psi
author_rank: Super Contributor
timestamp: November 27, 2019, 11:55:25 am
content: I had a similar digital sound on my audio which changed depending on mouse movement and what the PC was doing.It went away as soon as i switched to using the optical input on my speaker amp instead of phono jack.So i assumed it was just a ground loop coupling switchmode psu noise onto the line, which would vary with cpu load.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 12:21:10 pm
content: Quote from: Psi on November 27, 2019, 11:55:25 amMight be long shot, but do you think this one could eliminate the noise?https://www.thomann.de/gb/behringer_microhd_hd400.htmCorrect me if i am wrong, but if the ground gets lifted between the soundcard and the monitors, wouldn't that mean that the ground noise from the computer never would reach the monitors?And safety should not be a problem since all the gear is grounded in their respective power cables?I also should add that it seems like there is trouble in the communication between the firewire sound card and the computer. No audio plays, spotify or other audio software won't even play and the volume icon on the taskbar sometimes just shows a red warning symbol. Could this be some kind of power ground trampling a signal ground or the likes? Excuse my ignorance if this is total nonsense, just thinking out loud.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: November 27, 2019, 02:00:03 pm
content: Get analog mixer ( without USB ).Stop using USB for audio.Get ground in your power from the wall.Use a PS2 mouse.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 02:03:18 pm
content: Quote from: Jan Audio on November 27, 2019, 02:00:03 pmIf i were to construct a professional recording studio i might have opted for an analog solution, however; i want to do what i can with my current setup.The soundcard i am using now has a firewire connection and its own power supply.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: November 27, 2019, 02:27:06 pm
content: Quote from: magic on November 26, 2019, 09:41:27 pmHe says his records sound like shit.You dont record tru your speakers right ?Cant blame Yamaha here for.

author: magic
author_rank: Super Contributor
timestamp: November 27, 2019, 05:05:15 pm
content: Quote from: Vildhjarta on November 27, 2019, 11:12:26 amWell, there is something wrong and it should disappear. But the question is what it is.In my opinion you are simply hearing ground bounce of the PC. This is an unavoidable result of noisy current generated by the electronics flowing through the very low but non-zero resistance of ATX ground cables.In my opinion you are unlikely to reduce this noise significantly because you already use a PSU of reputable brand so the cables are probably of similar thickness as in any other reasonable PSU and not some hair-thin POS.And if I am right then you can avoid this noise altogether by using a USB isolator or grounding the audio interface to something quieter than the motherboard. This is what I would try.You can verify yourself that such noise exists: take headphones, touch some metal part of the case (or any other earthed object) with the tip, touch the ground of the headphone jack with a USB cable plugged into the computer. I bet you will hear the same crap. You may also do it with other computers to get a feel of how noisy they are. That Macbook should be quieter, for example.Quote from: Vildhjarta on November 27, 2019, 12:21:10 pm"Passive hum destroyer" - sounds like a pair of transformers so it should work.As for the guitar, the noise should go away if you grab a cable plugged into USB with one hand and wave the other hand over the pickups. That's what my theory predicts, at least.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: November 27, 2019, 05:17:28 pm
content: Quote from: Vildhjarta on November 27, 2019, 02:03:18 pmDo you have another computer to test ?Maybe it works.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 09:28:02 pm
content: Quote from: Jan Audio on November 27, 2019, 05:17:28 pmTested on a macbook, noise was absent.

author: Vildhjarta
author_rank: Contributor
timestamp: November 27, 2019, 09:30:25 pm
content: Quote from: magic on November 27, 2019, 05:05:15 pmYeah, i suppose there would be no reason for any grounding to go from the PC to the soundcard if the connection to real ground is broken.Which cures both the symptom (Noise and buzzing) and the issue itself (Ground going from PC through all the equipment and down through monitor power supply)

author: John B
author_rank: Frequent Contributor
timestamp: December 04, 2019, 10:41:26 pm
content: The solution may be simpler than you think. After months and months of trying to fix basically the exact problem, all it took was a 1 cent cap. Plus some jacks and a die cast case.The issue I had was with this setup:PC + focusrite 2i2 interface --->2 balanced lines ---> MOTU interface + Macbook Pro.The noise I had was exactly as described here: whenever the PC was utilising the CPU or mouse, lots of noise would be present on the MOTU outputs. However, all that was required to cause this was the grounds of the 2 interfaces being connected (ie conductive connection, important to note). The signal lines could be muted or even disconnected and the noise would still be present.I tried a USB isolator. Total waste of time and money. Not only did the PC not recognise the device, the isolated DC/DC supply caused it's own noise on the powered device.I tried (cheap) isolation transformers, whilst disconnecting the ground. This resulted in a very loud distorted 50Hz signal being superimposed on the audio signal. Tried reconnecting the grounds, and THAT sound went away, but the original noise came back. Not only that but the transformers had low frequency attention, distortion, and phase shift etc. They were cheap so that was expected.On a hunch, I tried connecting the grounds capacitively. Well what do you know, it fixed the issue immediately. Turns out there was a constant 78mV DC offset between the grounds. The required capacitance was somewhere around 10nF. With a 2.2nF cap, the 50Hz distorted sound was still there, but sounded different, then with 10nF it disappeared completely. Its odd, it wasn't like attenuation, there was a critical cap value where it just disappeared.So I tried connecting the balanced lines conductively, but connecting the grounds capacitively with a 100nF PP cap. Issue fixed, no need for isolation transformers.

author: John B
author_rank: Frequent Contributor
timestamp: December 04, 2019, 10:50:56 pm
content: Other things to note: the 78mV DC offset is also present between the 2 balanced lines (open circuit), and 1.5uA DC of current between the 2i2 and MOTU on each balanced line (when connected). Significance? I'm not sure whether that is something that needs rectifying or not.

author: magic
author_rank: Super Contributor
timestamp: December 05, 2019, 10:57:41 am
content: Now open your PC's PSU, unscrew that useless green-yellow wire from the chassis, put it back together and watch the fireworksWhich is to say, I still think a pair of diodes would be a good idea.

author: John B
author_rank: Frequent Contributor
timestamp: December 05, 2019, 10:41:23 pm
content: I just tried another solution. I ran a dedicated mains earthing strap directly to the ground shield of the balanced lines. There was about 50mV offset between the signal ground and mains earth ground, and about 50mA DC when shorted.It did greatly attenuate the noise, but I think I can still hear it there. Certainly enough to be tolerable for generable use, but not really studio grade.Still impressed by the cap solution. Totally eliminates the noise.

author: John B
author_rank: Frequent Contributor
timestamp: December 05, 2019, 10:51:15 pm
content: So, on the scarlett interface, the balanced output grounds are NOT connected to mains earth / PC chassis ground. There's about 500kbetween them. That goes towards explaining the high current to mains ground. There's about 80mA, while on the MOTU side it's balanced pair grounds are connected to mains earth and only get about 500uA DC leaking to ground.