Author Topic: Unwanted digital noise (Not the standard noise floor) from studio monitors  (Read 4981 times)

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Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #25 on: November 27, 2019, 06:58:25 am »
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/
The noise came anywhere i touched the cable.

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.
Does this apply to firewire cables as well?
The sound card i am using now is connected via firewire through a PCI-mounted firewire controller.
Googling shows similar reports from others, so yeah, maybe unforgiving Yamaha's.
So 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?
 

Offline magic

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #26 on: November 27, 2019, 08:44:31 am »
The noise came anywhere i touched the cable.
Perhaps 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 idiot ;D

Does this apply to firewire cables as well?
Yes. The point is to isolate all audio gear from the noisy ground of the PC.

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?
It'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 away |O More recently the smarter ones are buying USB isolators.
 
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Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #27 on: November 27, 2019, 09:07:36 am »
It'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 away |O More recently the smarter ones are buying USB isolators.
Well, 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 ;D
 

Offline magic

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #28 on: November 27, 2019, 10:34:53 am »
Would be really cool to have one of you guys troubleshooting the gear IRL though, too bad i live up in cold Norway ;D
Write a letter to Santa or hire somebody :P
I do it for free to the extent that it's an opportunity to milk you for data ;D

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.
The 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.
« Last Edit: November 27, 2019, 10:38:48 am by magic »
 

Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #29 on: November 27, 2019, 11:12:26 am »
Would be really cool to have one of you guys troubleshooting the gear IRL though, too bad i live up in cold Norway ;D
Write a letter to Santa or hire somebody :P
I do it for free to the extent that it's an opportunity to milk you for data ;D

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.
The 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.
I 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!
 

Offline Psi

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #30 on: November 27, 2019, 11:55:25 am »
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.
Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #31 on: November 27, 2019, 12:21:10 pm »
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.
Might be long shot, but do you think this one could eliminate the noise?

https://www.thomann.de/gb/behringer_microhd_hd400.htm

Correct 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.
« Last Edit: November 27, 2019, 02:00:26 pm by Vildhjarta »
 

Offline Jan Audio

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #32 on: November 27, 2019, 02:00:03 pm »
Get analog mixer ( without USB ).
Stop using USB for audio.
Get ground in your power from the wall.
Use a PS2 mouse.
 

Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #33 on: November 27, 2019, 02:03:18 pm »
Get analog mixer.
Stop using USB for audio.
Get ground in your power from the wall.
Use a PS2 mouse.
If 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.
 

Offline Jan Audio

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #34 on: November 27, 2019, 02:27:06 pm »
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's :-- for Yahama.

He says his records sound like shit.
You dont record tru your speakers right ?
Cant blame Yamaha here for.
 

Offline magic

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #35 on: November 27, 2019, 05:05:15 pm »
I 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.
Well, 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.

Might be long shot, but do you think this one could eliminate the noise?

https://www.thomann.de/gb/behringer_microhd_hd400.htm
"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.
 

Offline Jan Audio

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #36 on: November 27, 2019, 05:17:28 pm »
If 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.

Do you have another computer to test ?
Maybe it works.
 

Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #37 on: November 27, 2019, 09:28:02 pm »
If 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.

Do you have another computer to test ?
Maybe it works.
Tested on a macbook, noise was absent.  :)
 

Offline VildhjartaTopic starter

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #38 on: November 27, 2019, 09:30:25 pm »
Might be long shot, but do you think this one could eliminate the noise?

https://www.thomann.de/gb/behringer_microhd_hd400.htm
"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.

Yeah, 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)
 

Offline John B

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #39 on: December 04, 2019, 10:41:26 pm »
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.
 

Offline John B

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #40 on: December 04, 2019, 10:50:56 pm »
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.
 

Offline magic

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #41 on: December 05, 2019, 10:57:41 am »
Now open your PC's PSU, unscrew that useless green-yellow wire from the chassis, put it back together and watch the fireworks >:D

Which is to say, I still think a pair of diodes would be a good idea.
 

Offline John B

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #42 on: December 05, 2019, 10:41:23 pm »
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.
 

Offline John B

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Re: Unwanted digital noise (Not the standard noise floor) from studio monitors
« Reply #43 on: December 05, 2019, 10:51:15 pm »
So, on the scarlett interface, the balanced output grounds are NOT connected to mains earth / PC chassis ground. There's about 500k  \$\Omega\$ between 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.
 


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