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What is a "cross-coupled" TRS?
Old 10th December 2019
  #31
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samwinston123's Avatar
 

Quote:
Originally Posted by camadair View Post
Thanks. It sounds like cell signal interference to me because its closer to a cell phone near a car radio than it is to the other rfi examples Ive listened to online here: http://www.arrl.org/sounds-of-rfi . I also read hvac, solar inverters, among other things emit 4k. Why do you say its a cell tower?


It is definitely radiated and not conducted. I plugged a single coil guitar into a battery amp to use as a HF analyzer and voila. With the amp volume all the way down, the exact same sputtering and 4k chirp was lucid. It gets worse near the ceiling and at two walls. Going to walk the whole building with the amp tomorrow.

I bought 20 ferrite clips but this interference is extremely strong. Im going to talk to the power company, fcc, building electrician and property owner. Not sure what to do. All this equipment and the only thing that works are the acoustic instruments, not to mention having moved a piano into here. What a nightmare.

Suggestions welcome/ needed.
I should say I'm not absolutely sure it's cell interference, but the 2k intervals and the chirping are indicative from my experience. The fact that it's in all of your equipment points to a very strong, stationary source. It could be a high power wifi antenna or similar. There are several websites that have maps of cell tower locations.

This type of issue is the most difficult to deal with, as it's often caused by a huge variety of factors often outside of your control. Just as an aside, I work at a very nice studio that's out in the country. It was built from the ground up for audio and every precaution was taken to ensure proper grounding and noise immunity. There's a spike in the noise floor at 24kHz. After some digging, I found that it's caused by a huge Naval antenna some miles away that's used to communicate with submarines underwater.

https://en.wikipedia.org/wiki/Jim_Cr..._Radio_Station

Last edited by samwinston123; 10th December 2019 at 09:08 PM.. Reason: Safety First!
Old 10th December 2019
  #32
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Quote:
Originally Posted by samwinston123 View Post
I should say I'm not absolutely sure it's cell interference, but the 2k intervals and the chirping are indicative from my experience. The fact that it's in all of your equipment points to a very strong, stationary source. It could be a high power wifi antenna or similar. There are several websites that have maps of cell tower locations.

Do you have any plumbing in your space, and are the pipes copper? If so, you can try grounding some of your equipment there and see if it does anything.

This type of issue is the most difficult to deal with, as it's often caused by a huge variety of factors often outside of your control. Just as an aside, I work at a very nice studio that's out in the country. It was built from the ground up for audio and every precaution was taken to ensure proper grounding and noise immunity. There's a spike in the noise floor at 24kHz. After some digging, I found that it's caused by a huge Naval antenna some miles away that's used to communicate with submarines underwater.

https://en.wikipedia.org/wiki/Jim_Cr..._Radio_Station
DON'T DO IT. You can't just run a chassis/equipment ground to plumbing. If your electrical system's ground isn't bonded to the plumbing then you can create a shock hazard by connecting any equipment to the plumbing.

There are also cases where a proper bond can be seen from plumbing to electrical panel BUT a repair has been made somewhere else using PEX or plastic and the bond is actually broken.
2002 National Electrical Code sections 250.130(C)(1) and 250.52(A)(1).
Old 10th December 2019
  #33
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Quote:
Originally Posted by DownTheLine View Post
DON'T DO IT. You can't just run a chassis/equipment ground to plumbing. If your electrical system's ground isn't bonded to the plumbing then you can create a shock hazard by connecting any equipment to the plumbing.

There are also cases where a proper bond can be seen from plumbing to electrical panel BUT a repair has been made somewhere else using PEX or plastic and the bond is actually broken.
2002 National Electrical Code sections 250.130(C)(1) and 250.52(A)(1).
Yes you are correct. It was a lapse in judgment. You need to check for any potential difference before trying this. Better to just get a licensed electrician to look at the system.
Old 10th December 2019
  #34
Gear Addict
 

I am in northern cali but if I was in LA I would help you out. I know I have said this before but what you need to do is process of elimination.

This is how I would start.

1. Turn off any WiFi, modems you have in building.
2. Turn off all lights, HVAC, etc.

3. Turn on computer and only have your Symphony plugged in.

4. Turn your own cell phone off.

Now you will monitor the signal/noise floor at each stage of adding things back in

FIRST rule out wifi/modem interference, electrical syste issues

5. Turn on modem on, then router

6. Turn all lights on, turn HVAC on,

7. Plug each input/output back into your Symphony, If you have the model with DB-25 then you can try plugging input in first, monitor, then output.

8. Turn on each other piece of gear one at a time and test each piece before and after you plug it into the system/patch bay.

If at any time a piece of gear causes the noise then make a note of it, turn it back off, and continue with the process for the rest of the gear.

9. At last turn on your own cell phone

This is a standard process for this type of issue and has works gear but is time consuming.

If you find a piece of gear that causes an issue you can then try RF shielding.
Old 11th December 2019
  #35
Gear Addict
 

From Flea regarding hooking up from power supply to unbalanced pre amp.

the pin 2 is hot,
join pins 1 and 3

Best wishes,
FLEA microphones


For RF reasons the shield should be attached at both ends.
Old 12th December 2019
  #36
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camadair's Avatar
 

Problem identified: This is what the other side of the ceiling looks like.
Attached Thumbnails
What is a "cross-coupled" TRS?-img_7811.jpg   What is a "cross-coupled" TRS?-img_7812.jpg   What is a "cross-coupled" TRS?-img_7815.jpg   What is a "cross-coupled" TRS?-img_7817.jpg  

Last edited by camadair; 12th December 2019 at 03:21 AM..
Old 12th December 2019
  #37
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brianroth's Avatar
 

OMG! What a mess to have "mere feet" away from an audio system. Faraday cage seems needed.

Bri
Old 12th December 2019
  #38
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camadair's Avatar
 

Im very glad the problem is clear but am still in need a solution.

Some questions for the geeks:

Whats the most cost effective way to cover an entire ceiling (roughly 1000sq ft) with faraday material?

Does the FCC or any other institution have anything to say about this?

Do I have legal recourse, at least enough to break a lease?

Given that this is ten feet from my head, radiating my and everyone else's brain tissue around the clock, should we just get the hell out of here?
Old 12th December 2019
  #39
Gear Addict
 

Quote:
Originally Posted by camadair View Post
Im very glad the problem is clear but am still in need a solution.

Some questions for the geeks:

Whats the most cost effective way to cover an entire ceiling (roughly 1000sq ft) with faraday material?

Does the FCC or any other institution have anything to say about this?

Do I have legal recourse, at least enough to break a lease?

Given that this is ten feet from my head, radiating my and everyone else's brain tissue around the clock, should we just get the hell out of here?
Yes, I would break lease and get the hell out of there. Totally not cool that they have that inside and didn't disclose it.
Old 12th December 2019
  #40
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samwinston123's Avatar
 

Quote:
Originally Posted by camadair View Post
Problem identified: This is what the other side of the ceiling looks like.
Holy hell I guess I was right.

Seems like the tin foil isn't such a silly idea after all...
Old 12th December 2019
  #41
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brianroth's Avatar
 

It's above my pay-grade, but what I've read over the years indicates that the entire room....ceiling, walls, floors....has to be totally encased in some sort of conductive metal. That includes doors and windows. RF can sneak around! I read about installations in high RF environments, like in a building with radio broadcast transmitters, where they used fine mesh copper screen (like a window screen in a house....but copper) to curb the problems.

1000 sq feet implies something like 30' x 30' if it is square. That's a LOT of metal if you also include the walls and floor. In an earlier posting you also mentioned that the AC power was dicey. I dunno......maybe bail out?

Bri
Old 2 weeks ago
  #42
Quote:
Originally Posted by camadair View Post
Im very glad the problem is clear but am still in need a solution.

Some questions for the geeks:

Whats the most cost effective way to cover an entire ceiling (roughly 1000sq ft) with faraday material?

Does the FCC or any other institution have anything to say about this?

Do I have legal recourse, at least enough to break a lease?

Given that this is ten feet from my head, radiating my and everyone else's brain tissue around the clock, should we just get the hell out of here?
any update on this? Did you leave or find a way to solve the problem?
Old 1 week ago
  #43
Gear Nut
 
camadair's Avatar
 

I hope everyone had a good holiday.

ATT sent out a "third party" testing company, EBI Consulting. It's in quotes because there are a lot of dubious conflicts of interest involved here with ATT, testing companies, FCC, etc...

This company used a Narda NBM 550 Broadband Field Meter and a Narda EA Probe shaped probe 2402/07B

They measured the highest levels of broadband RF interference as a spacial average in the studio to be .193 W/m^2 however this was initially expressed as FCC General Public MPE (Maximum Permissible Exposure) and took some pressing to find out what the measurement was expressed in watts.

The noise floor on everything is totally useless. Mostly the condenser microphones and anything unbalanced or antenna-like: guitar amps and equipment, tape machines, etc.. The mics are basically antennas for the RFI: if you point them toward the ATT antennas, the whining, ringing, and chatter gets louder (not surprising).

I was told ATT has two divisions that handle this type of thing but im unclear what the job is of the ATT people Im dealing with. One is the Sr. RAN of Wireless Engineering, Const. & Ops. (don't ask me what that stands for). I think they've pushed me over to their lawyer at this point.
Old 1 week ago
  #44
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Radardoug's Avatar
 

So, simple answer, get out of there. If you dont the headaches will be endless!
Old 1 week ago
  #45
Gear Addict
 

Quote:
Originally Posted by camadair View Post
I hope everyone had a good holiday.

ATT sent out a "third party" testing company, EBI Consulting. It's in quotes because there are a lot of dubious conflicts of interest involved here with ATT, testing companies, FCC, etc...

This company used a Narda NBM 550 Broadband Field Meter and a Narda EA Probe shaped probe 2402/07B

They measured the highest levels of broadband RF interference as a spacial average in the studio to be .193 W/m^2 however this was initially expressed as FCC General Public MPE (Maximum Permissible Exposure) and took some pressing to find out what the measurement was expressed in watts.

The noise floor on everything is totally useless. Mostly the condenser microphones and anything unbalanced or antenna-like: guitar amps and equipment, tape machines, etc.. The mics are basically antennas for the RFI: if you point them toward the ATT antennas, the whining, ringing, and chatter gets louder (not surprising).

I was told ATT has two divisions that handle this type of thing but im unclear what the job is of the ATT people Im dealing with. One is the Sr. RAN of Wireless Engineering, Const. & Ops. (don't ask me what that stands for). I think they've pushed me over to their lawyer at this point.
Book it! run for the hills, of the beach
Old 5 days ago
  #46
Does anyone have any recommendations on how to build faraday cages for just my monitors? Bad cell tower interference. Moving is not an option right now.
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