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High pitch noise coming from microphone.

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High pitch noise coming from microphone.

PostPosted: Mon Feb 11, 2019 4:58 am
by Wyatt Rad
I bought my Audio Technica AT2020 and Behringer U-Phoria UM2 about 3 months ago. Through my computer, the audio always comes out with this high pitch squeal like sound. It is very faint but still very noticeable. Whenever I move the mic around the pitch waivers. The XLR cable I use is just the Amazon Basics 6 ft cable. The sound only appears through my computer, and doesn't show up when listening through the Direct monitoring on the preamp. Around me I have a printer, my desktop, 3 screens, my speakers, desk lamp, and a fan (which doesn't have to be on or off to hear the noise). I can push the gain on the preamp up or down, and it doesn't change the volume or pitch of the noise, however turning the volume of my mic up or down through microphone properties on my pc does change the volume (and it goes away completely around 75%... I would prefer to get rid of the sound rather than turning it down to 75 because using things like compressors brings the sound back out)

I don't think it is the microphone because like I said, it doesn't come out when listening through the direct monitoring on the preamp, only on my pc. If you would like a recording of what it sounds like I can make one. It sounds similar to when your getting your teeth cleaned at the dentist. A weird comparison I know but it's accurate haha

I bought the mic used, however they said it was in perfect condition minus the few visual defects (A few scratches in the paint)

Re: High pitch noise coming from microphone.

PostPosted: Mon Feb 11, 2019 10:41 am
by Hugh Robjohns
There are a number of possible things this could be, but the most likely is a probably ground-loop problem. What are your speakers and what kind of cable are you using to connect them to the interface?

If you're not already, I'd suggest making sure the speakers are powered from the same mains plug-board as the computer (and interface), and use balanced audio cables for the monitors.

If those two actions don't cure it, then it may be necessary to isolate the screen grounds of the audio cables to break any hum loops, and that can either be done by snipping and isolating the cable screens inside the plugs (at the speaker ends), or by using a line isolating transformer box, like the ART DTI in the speaker feeds.

H

Re: High pitch noise coming from microphone.

PostPosted: Mon Feb 11, 2019 4:29 pm
by Martin Walker
Yep, Hugh is probably on the money yet again, so here's my SOS step-by-step guide to tracking down ground loop problems. Hope it helps!

https://www.soundonsound.com/sound-advi ... -my-studio

Oh, and welcome to the SOS Forums Wyatt Rad! 8-)


Martin

Re: High pitch noise coming from microphone.

PostPosted: Wed Feb 13, 2019 2:20 am
by Wyatt Rad
Hugh Robjohns wrote:There are a number of possible things this could be, but the most likely is a probably ground-loop problem. What are your speakers and what kind of cable are you using to connect them to the interface?

If you're not already, I'd suggest making sure the speakers are powered from the same mains plug-board as the computer (and interface), and use balanced audio cables for the monitors.

If those two actions don't cure it, then it may be necessary to isolate the screen grounds of the audio cables to break any hum loops, and that can either be done by snipping and isolating the cable screens inside the plugs (at the speaker ends), or by using a line isolating transformer box, like the ART DTI in the speaker feeds.

H

I don't think this is a ground loop problem... I have tried this on my desktop pc and on a battery powered laptop. The audio interface is usb powered and isn't in anyway connected to my speakers or the headphones I'm listening to them through. I found a thread on another website and I think they had the same issue as me. Some solutions were that the DAC/ADC had bad isolation so they should use an interface with isolated DACs and ADCs or provide isolated power from the power supply. Other people suggested a Ferrite Ring... not really sure what the best route of action for something like this would be... I thought about buying a separate phantom power supply but I don't think that would work... I can turn the phantom power my audio interface supplies on and off and the sound still happens (whether the microphone is on or off)...

Re: High pitch noise coming from microphone.

PostPosted: Wed Feb 13, 2019 8:26 am
by ef37a
I suspect the UM2 (though Behringer are careful not to tell us!) is a 16 bit device. The fact that it has a maximum sampling rate of 48kHz and is a USB 1.1 device adds weight to my thoughts.

Now, cheap (sorry but it is!) 16 bit converters can suffer a "USB whine". This is inherent in the converter and can only be mitigated by setting the record level very low in Windows Sounds.

Get into Win Sound's menu and first check that the UM2 is set as Default record and play device. Then work through the menus to get to "level" and you will find I am sure it is set to 100%. Knock it back to 5%, not a typo, five. Set playback to 100%.

This should push the noise down close to the noise floor but it can still be seen if you run a silent recording through an analyser such as Right Mark A.

Dave.

Re: High pitch noise coming from microphone.

PostPosted: Wed Feb 13, 2019 10:38 am
by CS70
Just to get the obvious out of the way, you don’t have the speakers turned on when you operate the mic, right?

Re: High pitch noise coming from microphone.

PostPosted: Wed Feb 13, 2019 10:50 am
by Wonks
ef37a wrote:I suspect the UM2 (though Behringer are careful not to tell us!) is a 16 bit device. The fact that it has a maximum sampling rate of 48kHz and is a USB 1.1 device adds weight to my thoughts.

It's certainly weird. Behringer quote a dynamic range of 100dB for the UM2, which means it must have more than a 16-bit A/D converter (96dB dynamic range maximum ignoring noise). Or else they are telling porkies.

But 100dB equates to less than 17-bits. So they might be using an 18 or 20-bit A/D converter and throwing away some bits (or they are taken up by circuit noise). I can't imagine they'd be using a 24-bit converter and wasting all of the possible 44dB extra dynamic range available. Some of the older Behringer rack processors used 18 and 20 bit A/Ds, so maybe they have a big stockpile of those chips they wanted to use, or maybe they were just the cheapest means of making a very low-cost interface.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 4:12 am
by Wyatt Rad
CS70 wrote:Just to get the obvious out of the way, you don’t have the speakers turned on when you operate the mic, right?

Yes I have made sure the speakers are off (and completely unplugged from my system...) haha

ef37a wrote:I suspect the UM2 (though Behringer are careful not to tell us!) is a 16 bit device. The fact that it has a maximum sampling rate of 48kHz and is a USB 1.1 device adds weight to my thoughts.

Now, cheap (sorry but it is!) 16 bit converters can suffer a "USB whine". This is inherent in the converter and can only be mitigated by setting the record level very low in Windows Sounds.

Get into Win Sound's menu and first check that the UM2 is set as Default record and play device. Then work through the menus to get to "level" and you will find I am sure it is set to 100%. Knock it back to 5%, not a typo, five. Set playback to 100%.

This should push the noise down close to the noise floor but it can still be seen if you run a silent recording through an analyser such as Right Mark A.

Dave.

I'm not gunna lie.... not exactly sure where the playback section you want me to set to 100% is but I think the 16 bit audio is the cause...... At this point however I think I'm looking into something more like the Focusrite Scarlett or another alternative. If anyone has any ideas for a more affordable audio interface that isn't going to give me this usb whine I'm all ears :)

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 8:44 am
by ef37a
Wonks wrote:
ef37a wrote:I suspect the UM2 (though Behringer are careful not to tell us!) is a 16 bit device. The fact that it has a maximum sampling rate of 48kHz and is a USB 1.1 device adds weight to my thoughts.

It's certainly weird. Behringer quote a dynamic range of 100dB for the UM2, which means it must have more than a 16-bit A/D converter (96dB dynamic range maximum ignoring noise). Or else they are telling porkies.

But 100dB equates to less than 17-bits. So they might be using an 18 or 20-bit A/D converter and throwing away some bits (or they are taken up by circuit noise). I can't imagine they'd be using a 24-bit converter and wasting all of the possible 44dB extra dynamic range available. Some of the older Behringer rack processors used 18 and 20 bit A/Ds, so maybe they have a big stockpile of those chips they wanted to use, or maybe they were just the cheapest means of making a very low-cost interface.

Maybe not quite porkies Wonks but what is 96dB with some form of "weighting"?
The odd thing is, iirc the little UCA202 16 bit AI does not suffer the problem but I have one to hand, will check.

Oi'm beck. Yes, no spurious tones show in Right mark except a 50Hz hum popping in 12dB above the noise floor. The latter is at -84dBfs in Samplitude and is rather "thick" and messy but no spikes. The hum is probably due to me leaving the 202 next to a PC and printer? Still at -72dBfs, not bad for 20 quid!

Dave.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 10:09 am
by blinddrew
Wyatt Rad wrote:At this point however I think I'm looking into something more like the Focusrite Scarlett or another alternative. If anyone has any ideas for a more affordable audio interface that isn't going to give me this usb whine I'm all ears :)
The thing is, if you've got an issue with the set up rather than the interface, you might just transfer the issue to the new device. Best to try and isolate the cause first.
Do you have any mates with an interface that you can borrow from to test it?

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 10:46 am
by James Perrett
The noises that Dave is referring to are more correctly called Idle Tones and are an artefact of the Sigma Delta analogue to digital conversion method used in most audio convertors. These tones occur when the signal is at or close to zero.

Better convertors don't suffer from these tones but I have a fairly recent Behringer UCA222 that does suffer from them and it is possible that the UM2 uses similar convertors. My UCA222 uses the same circuit board as the 202 but it is possible that the circuit has been changed over the years which would explain why Dave's older 202 is fine but my 2017 vintage one suffers from these noises.

I'm still not sure whether this is what the OP is hearing - it may just be a lack of a good ground rather than a ground loop that is causing the problem.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 10:50 am
by blinddrew
James Perrett wrote:I'm still not sure whether this is what the OP is hearing - it may just be a lack of a good ground rather than a ground loop that is causing the problem.
I did wonder about that but the OP has had the same issue on desktop as well as laptop, and it would be fairly rare for a desktop to be class II wouldn't it?

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 10:58 am
by ef37a
Hi James, I first became aware of these tones when I tried USB recording with an early mark A&H Zed10 USB mixer.
I had been using the mixer for some time feeding a 2496 card (5mtr balanced cabled to a 10k-10k traff box into the card) That setup gave me a noise floor of -93dBfs, all mixer controls at zero. Then I thought I would give USB a go. I was appalled at the row!

Really obvious whining noises. A&H were swift in their aid and, as you say, explained that the tones were inherent in that series of converters. They did give me chapter and verse as to how to minimize them and USB recording could be made good enough for noisy stuff, front of a guitar cab say but could not approach the 24 bit 2496 noise floor.

Important to say. All the A&H range are now 24 bit capable and, AFAIK, close to -100dBfs.

Dave.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 11:04 am
by ef37a
blinddrew wrote:
James Perrett wrote:I'm still not sure whether this is what the OP is hearing - it may just be a lack of a good ground rather than a ground loop that is causing the problem.
I did wonder about that but the OP has had the same issue on desktop as well as laptop, and it would be fairly rare for a desktop to be class II wouldn't it?

Depends where the earth pin goes Drew! People can have houses with poor, even no earth for years and never know.

Dave.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 11:21 am
by James Perrett
blinddrew wrote:I did wonder about that but the OP has had the same issue on desktop as well as laptop, and it would be fairly rare for a desktop to be class II wouldn't it?

If there are just a few ohms of resistance in the earth line it will cause problems. If the earth has to go through a few PCB tracks on the way to the interface then that would be enough to cause an issue. I've had exactly this problem recently with my laptop and connecting one of the audio cables from the interface to a well grounded bit of kit fixed things.

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 11:46 am
by blinddrew
I stand corrected! :)

Re: High pitch noise coming from microphone.

PostPosted: Sun Feb 17, 2019 11:48 am
by Wonks
blinddrew wrote:I stand corrected! :)

...said the man in the orthopaedic shoes.