500 hz problem

[Neumann Peluso]

In the process of setting up my new studio and have a problem with a hum. Tried everything from from ground lifts, plugging in each piece of gear individually, isolation transformer. An electrician came out and said the ground is fine. Tried different eqs and found the noise around 500hz. The noise comes through just about every piece of gear which worked fine in my previous studio. What could be interfering in that frequency? Has anyone had a similar problem before?

[RawDepth]

Hi and welcome,

I have had a similar problem while running live sound in a nightclub. I later learned that if you have low voltage signal cables (mic, instrument, line level, sends, returns) running next to higher voltage cables (amp-to-speaker or AC power) they can cause some noise in the system. It is okay to cross them perpendicular but not to run them touching each other side-by-side for any distance.

Try not to tie your cables all together in tight bundles, unless you have them well sorted and compatible.

What kind of rig do you have? All separate analog gear? A computer with monitors? US or Europe?

[stainless]

Welcome Neuman!

Have you tried unplugging all inputs to your board DAW? do you still hear it? or is everything connected?

if you have your system gain up... can you by any chance hear any radio in the background (no matter how faint)?

I had a problem with a constant "noise and at hi gain I could hear a radio station faintly in the background-

I had hardwired (in the wall) an low Z set of outputs to my power amps for the control rool... and had inadvertanly reversed pins 1 and 2 on 1 of the connections

it was only by disconnecting everything and connecting one thing at a time using a known/good/test cable that I found this... and it took me hours to find something that took less than 10 minutes to fix



don't know if that's it, but I'm guessing it's an induced signal (like Rawdepth suggested) or a cable acting as a poor antennae

where are you located 60Hz power or 50 Hz?

[Neumann Peluso]

Hi and welcome,

I have had a similar problem while running live sound in a nightclub. I later learned that if you have low voltage signal cables (mic, instrument, line level, sends, returns) running next to higher voltage cables (amp-to-speaker or AC power) they can cause some noise in the system. It is okay to cross them perpendicular but not to run them touching each other side-by-side for any distance.

Try not to tie your cables all together in tight bundles, unless you have them well sorted and compatible.

What kind of rig do you have? All separate analog gear? A computer with monitors? US or Europe?

Hi Raw Depth,
Thanks so much for the advice. I'm located in the US running a tower and flat monitor running Sonar 6 and Pro Tools. I have some outboard gear in a rack and a 16 channel analog mixer which I intend to upgrade sometime soon. Most of my cables are relatively new or in very good shape but I'll still check them all. I have a wall & window between the control room and live room with a 16 channel xlr patch bay that has been hand wired all with twisted pair wiring. The patch bay is connected to the mixer with a brand new Mogami snake.
I did read somewhere about the power cables crossing the audio cables perpendicular so I have tried that. Much of the noise has come straight from the outlets even when the gear is plugged in on it's own, separate from everything else. I don't not here the noise during playback when only the computer, sound card and monitors are in use but have heard it in my mixer, headhone amp etc.

Thanks 

[Neumann Peluso]

Hi Stainless and thanks so much. I had not noticed the noise at first when I was just playing back some music while setting up. When I started to test everything out and plugged in a mic is when all the trouble started and the more I investigated the more I heard the noise. We did hear some radio interference when plugged into one of my outlets in the wall. It wasn't super loud but any bit of it is too much.

I've heard the noise just from plugging in each piece separately (the mixer plugged into the wall with nothing else attached to it listening through the headphone jack) and even my headphone amp, not plugged into anything but the outlet and me listening through headphones. I even plugged my Otari tape machine into just the outlet and plugged my headphones in and could hear the noise there too. I don't hear it when the gain is turned low but when it's cranked, you can hear it plain as day. I'm located in the US.

Could It be a harmonic in the power perhaps? If so would you know how to kill it?

Thanks so much!

Welcome Neuman!

Have you tried unplugging all inputs to your board DAW? do you still hear it? or is everything connected?

if you have your system gain up... can you by any chance hear any radio in the background (no matter how faint)?

I had a problem with a constant "noise and at hi gain I could hear a radio station faintly in the background-

I had hardwired (in the wall) an low Z set of outputs to my power amps for the control rool... and had inadvertanly reversed pins 1 and 2 on 1 of the connections

it was only by disconnecting everything and connecting one thing at a time using a known/good/test cable that I found this... and it took me hours to find something that took less than 10 minutes to fix



don't know if that's it, but I'm guessing it's an induced signal (like Rawdepth suggested) or a cable acting as a poor antennae

where are you located 60Hz power or 50 Hz?

[stainless]

sounds like the problem is with your utilities- In California the power companies voltage tolerance can range a plus or minus 10 -15% which means... and for things like motors and lighting this is within the range that they will work at- audio gear is another issue- I onvce played at a Grange Hall- anything that used a 'wall wart' didn't work- the AC power measured out of the outlets was 102 volts.. apparently below the minimum power requirements the wall warts (and devices attached to them) need.

You may need a power conditioner or one of these (see link below) might be all that's needed. I have heard that these do eliminate the hum

http://www.audiomidi.com/Hum-X-Ground-Hum-Exterminator-P4803.aspx

I'm not endorseing this seller (or company for that matter)... it was the first link from my google search.

If you can hear a radio station, somewhere there's a wiring issue that's making a run act like an antennae. Any possibility one of your twisted pairs is reversed at one end?

good luck- I know I spent some major frustration till i finally uncovered it!

[dementedchord]

any light dimmers or florescent lights in the end you need to take it all down and put it back up checking one peice at a time anmd isolate it...

[stainless]

heh dementedchord

WELCOME to HRS- it's fairly quiet here, but in time ... who knows-

good advice about taking it all down-

dimmers and FL usually make noise at 60 Hz (or some multiple thereof)... though if he's in Europe... the 500 Hz would be a multiple of 50Hz power...

theatrical dimmers are beyond most of our re$ources (or at least I can think of other things to buy)

I recently switched to the energy saving mini FL's and haven't noticed a problem... though I did have a dimmer in the drum room that would add some noise in the middle of the range.... so I got lowr wattage bulbs and put in a SPST switch!

this stuff will make you crazy!

[RazorLand Studio]

Look through our cabling, if you have extra lengths coiled in straight coils, that could  be causing some of your hum problems. After 30 years of doing live sound, I have learned that any extra length of cable should be laid out in a figure 8 pattern instead of a straight single coil. What you do is actually build a field coil when wrapping it in a single coil, the figure 8 breaks up the vibrations that are inherent in signal flow, especially in any edison cable, ie: your power cords.  Give it a shot, also if you are running any outboard gear in a rack that has steel rails, use plastic washers to isolate the gear from the rack, that sometimes causes hum problems.

[stainless]

hadn't looked at this thread in a while... I wonder if there's a breaker panel in one of the walls common to the studio?

completely unrelated, but a friend had a large saltwater aquarium in his house up against an exterior wall that also had the main circuit panel on the same wall right behind where the aquarium was sitting. If you had a hand in the tank and touched the light fixtures you'd get a enough of a shock to make you jump.  The lighting fixture was fine, but if we tool a VoltOhm meter and put one  probe in the water and touched anything with an earth ground we measured ~80 VAC (at the lowest milliamp range the display would register a slight bit of activity and then back to zero)-  all created by the EMF from the panel behind. (and we even unplugged the pump, heater, etc)  He got a ground probe for the tank and problem solved. 

Perchance a similar thing is occurring here?

[RazorLand Studio]

Absolutely it could be, I have also experienced problems with hum and buzz generating from freezers, refrigerators, AC units, neon lights, ligh dimmers etc..........they are all culprits when chasing the elusive hummmmmmmm. Might also consider doing a star ground on just the circuits connected to the studio equipment, run a seperate ground rod outside and gang the grounds together and run them to that, sometimes it works, sometimes it doesnt. I would guess the problems are probably being generated from an inside the house source though, some sort of electric motor or conveyance that is running and causing noise.