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10KHZ Ground Noise in Studio
« on: March 17, 2016, 01:38:35 AM »
Hi,
I'm working at a studio at the moment were there's a present 10khz (actually is somewhere between 9.5Khz and 10Khz) in the Audio signals.

That noise is more present in Keyboards, Guitar and bass amplifiers and any signal I connect to a DI.
It's also present at mic signals although lower in level.

In some keyboards I was able to completely clean the signal by isolating the ground at the power plug (ground lift on the DI didnt stop the noise).
For the sake of testing I also isolated the ground at the power plug on guitar amps although with no improvements at all.

The Studio is at an industrial location, and was made at a warehouse over the years, it was a properly planned and implemented project so the electrical installations is of a warehouse and not a professional studio.

The Console and all the outboard are powered  through Furman PL-8 C E Power Conditioner's, that are speced with having "Noise Filtration - LiFT offers AC power filtering to ensure clean power for unequaled audio & video clarity" and "Isolated Banks - Isolated outlet banks minimize inter-component interference and noise contamination".

Backline like the guitar and bass amps are powered in the live room and connected to the normal wall power plugs.

The 10KHZ noise seems to be worse in some days than the others,  although the frequency is constant.

I would like to minimize this problem as much as possible, knowing that the studio is not mine, so I can't do a new and well planned electrical installation.

What might me the cause of this problem?
What could I do to test and find the culprit/culprits?
Any tests you could advise?

What could I do to minimize it?

Thank you so much




ruffrecords

Re: 10KHZ Ground Noise in Studio
« Reply #1 on: March 17, 2016, 05:22:42 AM »
The power conditioner will only stop noise getting in from the outside mains supply.  Sounds to me like you have something on the inside causing the interference. The most likely culprit is a switched mode power supply (SMPSU). Laptop power supplies can be culprits but any gear with a SMPSU in it can produce this sort of noise.

Cheers

Ian

gyraf

Re: 10KHZ Ground Noise in Studio
« Reply #2 on: March 17, 2016, 07:03:19 AM »
Monitor the noise, and switch off (unplug) everything connected to your power line one unit at a time until you find the noisy one.

If noise comes in with the mains voltage (from neighbor companies doing e.g. plasma cutting), talk to your electricity supplier - they'll know how to filter efficiently.

Jakob E.

..note to self: don't let Harman run your company..

JohnRoberts

Re: 10KHZ Ground Noise in Studio
« Reply #3 on: March 17, 2016, 11:43:22 AM »
A 10kHz noise could be coming directly from something switching @ 10kHz (or an unstable circuit oscillating), or indirectly as a beat frequency between two much higher frequency sources that aren't audible by themselves, but differ by the audible 10Khz.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Whoops

Re: 10KHZ Ground Noise in Studio
« Reply #4 on: March 17, 2016, 01:44:22 PM »
Thank you all for the advices, I will try that.

I will see if there's a possibility of testing it, listening the noise while unplugging everything one by one.

I don't think is something that simple like a laptop PSU, or a small switching PSU adapter, because that noise is present all the time, even with no laptop connected, it seems is more structural in the building itself (like lightning installation) or it comes from outside the building and as it's an industrial old area.

Will see, thank you

If you have any more ideas please let me know
 

JohnRoberts

Re: 10KHZ Ground Noise in Studio
« Reply #5 on: March 17, 2016, 02:13:15 PM »
Thank you all for the advices, I will try that.

I will see if there's a possibility of testing it, listening the noise while unplugging everything one by one.

I don't think is something that simple like a laptop PSU, or a small switching PSU adapter, because that noise is present all the time, even with no laptop connected, it seems is more structural in the building itself (like lightning installation) or it comes from outside the building and as it's an industrial old area.

Will see, thank you

If you have any more ideas please let me know
Unless the noise is in the last link of your audio chain.

Do you hear it in cans? Portable radio?  etc.... divide and conquer, troubleshooting 101.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Whoops

Re: 10KHZ Ground Noise in Studio
« Reply #6 on: March 17, 2016, 02:15:19 PM »
Thank you all for the advices, I will try that.

I will see if there's a possibility of testing it, listening the noise while unplugging everything one by one.

I don't think is something that simple like a laptop PSU, or a small switching PSU adapter, because that noise is present all the time, even with no laptop connected, it seems is more structural in the building itself (like lightning installation) or it comes from outside the building and as it's an industrial old area.

Will see, thank you

If you have any more ideas please let me know
Unless the noise is in the last link of your audio chain.

Do you hear it in cans? Portable radio?  etc.... divide and conquer, troubleshooting 101.

JR

I hear it when I record to protools DI signals, I hear it when I connect a guitar, bass or keyboard to an amplifier. I hear it from the guitar Amplifier even with no input jack connected, although much lower in volume, it's always there

thanks

JohnRoberts

Re: 10KHZ Ground Noise in Studio
« Reply #7 on: March 17, 2016, 03:54:16 PM »
Tinnitus?  (kidding)

No seriously maybe sniff around with a cheap AM portable radio.

Scope probe stuck in the air with a short piece of wire...

It's coming from somewhere, maybe everywhere.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

DarthFader

Re: 10KHZ Ground Noise in Studio
« Reply #8 on: March 17, 2016, 04:05:27 PM »
Look up Power-Line Communication. Same sort of thing happened at a studio I worked at. 16kHz from every guitar amp, even a battery-powered toy.

pucho812

Re: 10KHZ Ground Noise in Studio
« Reply #9 on: March 17, 2016, 10:33:06 PM »

 divide and conquer, troubleshooting 101.

JR

brilliant.
Every mic has a purpose it might be a door stop or a hammer, but every mic has a purpose.


Whoops

Re: 10KHZ Ground Noise in Studio
« Reply #10 on: March 18, 2016, 12:13:37 AM »
Tinnitus?  (kidding)

No seriously maybe sniff around with a cheap AM portable radio.

Scope probe stuck in the air with a short piece of wire...

It's coming from somewhere, maybe everywhere.

JR

Thanks John, will do that

I never done that before,  can you please elaborate on how to do that.

Do I connect the scope probe to the AM radio antenna?

DerEber

Re: 10KHZ Ground Noise in Studio
« Reply #11 on: March 18, 2016, 07:11:45 AM »
10kHz is a bit low for AM Radio, but maybe your 10kHz is derived from higher frequency, so try if you can tune and find some carrier or harmonics of the 10kHz.  And maybe you can even track were it comes from by walking around with the radio.
Battery powered radio is your friend.

bruno2000

Re: 10KHZ Ground Noise in Studio
« Reply #12 on: March 18, 2016, 09:36:41 AM »
Back in the 80s we had a problem with a "glitch" coming in on the power lines.  We could actually see it on a scope.  Turned out it was a bad large power transformer on the rail system 3 blocks away.......  Found it with a tape machine repro head connected to a battery operated guitar amp.
Best,
Bruno2000

0dbfs

Re: 10KHZ Ground Noise in Studio
« Reply #13 on: March 18, 2016, 11:51:27 AM »
I hope you appropriately sent Georgia Power or Marta an invoice!

Cheers,
jb

Music is everything!
Audio is everything else!

JohnRoberts

Re: 10KHZ Ground Noise in Studio
« Reply #14 on: March 18, 2016, 12:28:38 PM »
Tinnitus?  (kidding)

No seriously maybe sniff around with a cheap AM portable radio.

Scope probe stuck in the air with a short piece of wire...

It's coming from somewhere, maybe everywhere.

JR

Thanks John, will do that

I never done that before,  can you please elaborate on how to do that.

Do I connect the scope probe to the AM radio antenna?
I was talking about two different tests... sniffing for RF with a portable AM radio is one test, another is sticking a probe in the air with a short length of bare wire... scope probes are high impedance and high bandwidth so may see your noise, and where it is stronger.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

Whoops

Re: 10KHZ Ground Noise in Studio
« Reply #15 on: March 18, 2016, 02:20:18 PM »
Tinnitus?  (kidding)

No seriously maybe sniff around with a cheap AM portable radio.

Scope probe stuck in the air with a short piece of wire...

It's coming from somewhere, maybe everywhere.

JR

Thanks John, will do that

I never done that before,  can you please elaborate on how to do that.

Do I connect the scope probe to the AM radio antenna?
I was talking about two different tests... sniffing for RF with a portable AM radio is one test, another is sticking a probe in the air with a short length of bare wire... scope probes are high impedance and high bandwidth so may see your noise, and where it is stronger.

JR

Thanks

Pip

Re: 10KHZ Ground Noise in Studio
« Reply #16 on: March 18, 2016, 10:20:04 PM »
I have had a 10K problem for a while in a live situation that I deal with. We know what it is and it only is in the high gain vox mic channels so we gate it out. It comes from a pulse width modulated LED lighting dimmer that feeds LED tape. It is inductive into the mic cables that run near the ribbon cable that feeds the LED tape. That's all I got hope it helps!
Pip
New York City
http://geosonixlab.com

trobbins

Re: 10KHZ Ground Noise in Studio
« Reply #17 on: March 23, 2016, 08:38:34 PM »
If you had a laptop running a software spectrum analyser, like REW, then you could directly check for 10kHz signal from some of your 'sources' such as guitar amp or MIC.  With laptop not connected to anything, and showing a suitable noise floor, and then connected to a 'source', you could try and compare sources for their 10kHz levels (eg. devices not connected to anything but the laptop, compare to devices connected mains AC).  That may localise if signal is mains distribution related only.

Can you confirm there is no 10kHz when all inputs are disconnected, as well as connected but padded down.  That would localise to just connected devices.

Whoops

Re: 10KHZ Ground Noise in Studio
« Reply #18 on: March 24, 2016, 10:54:00 PM »
Can you confirm there is no 10kHz when all inputs are disconnected, as well as connected but padded down.  That would localise to just connected devices.

The noise is on  guitar amps even when inputs are disconnected, it's much lower in level but its there, if a guitar is connected is  much louder

The same noise is on every DI input I record, Bass and keyboards

It's also present in microphone signals if I have to turn the gain high, imagine a dynamic mic capturing an acoustic guitar, or a dynamic mic used for Room it's there, with condensers the the mic signal is louder so no need to turn that gain up on the Mic Pre for the 10khz to be noticeable


trobbins

Re: 10KHZ Ground Noise in Studio
« Reply #19 on: March 25, 2016, 12:44:23 AM »
I guess the issue is to confirm if the 10kHz signal is radiated in, or conducted in, to your analog sources  (eg. mic, guitar).  Some thoughts are:

The increase with guitar connected could be due to the guitar wiring having stray coupling to ground through a person, or from radiated pickup.

For example, if you could record the signal from a Mic in to a PC application running on a standalone device with no other electrical connections (eg.  iphone, or laptop), and could confirm that 10kHz was on the recording, then that indicates the signal is ingressing via radiation.  If the same action was done at another location, and there was no 10kHz, then that is good info.

Perhaps if you connect an unshielded lead to a DI, with a few meters of wiring to act as antenna, then observe whatever background signal the DI generates, and vary the orientation of the wiring, and when it is being handled.