WEIRD! my "hum" problem goes away when screen is off!

mano · Post by **mano** » Mon May 06, 2002 6:49 am

wow how weird!

I've been one of those HUM-GROUND-LOOP people ever since I started my home-studio. Well something funny occured today. I realized that the HUM goes away as soon as I turn my computer monitor (Screen) off (!?)

Why do you think is it doing this? I know that cathodic-tubes are basically electron-guns (sounds like Star Trek I know), and that it could cause some electrical disturbance, but wow guys all my hum problem gets solved as soon as this thing is off.

Now... What should I do, Change my screen? It is a nice NEC FE950 (19"). I even tried to change the resolution, but it doesnt change anything... Only if I turn it off.

bosone · Post by **bosone** » Mon May 06, 2002 8:33 am

my monitor interfere only with my guitar...
i'd like to buy an LCD screen... a bit expansive, but absolutely no unwanted noise!

Neutron · Post by **Neutron** » Mon May 06, 2002 9:03 am

Somewhere there is either too much current being drawn from your electrical circuit by your monitor, causing low voltage in something else. or more likely there a wire or something that is picking up the HUGE amount of electromagnetic radiation from the monitor.

try this first if it is practical. turn the monitor on, and once you get a nice hum try picking up and moving it back and forth to see which way makes the hum get louder, and which makes it get quieter.
(watch your back lifting heavy objects!)

maybe the hum will go down as soon as you lift it. whats underneath? are there wires running near the monitor? analog line wires can pick up noise easilly.

take a picture if you have a digicam

orbita · Post by **orbita** » Mon May 06, 2002 12:30 pm

hm thought id already posted a reply to this but must have dreamt it!

anyway.. my advice is to check that you dont have audio cables running in parallel with your monitor cables - both the power and the vga. Ideally keep audio cables far away from power and vga cables but if you can't at least make sure they run at right angles to each other. If you wiggle your cables you may find one that is causing hum.

If you have to have audio cables near other electrical cables make sure they are good quality shielded cables.

Keep wall warts away as well they generate awful hum.

Neutron · Post by **Neutron** » Mon May 06, 2002 8:28 pm

Yes and i saw your reply. it was in a different thread (or maybe i dreamt that as well!)

mano · Post by **mano** » Tue May 07, 2002 8:14 pm

guys thank you for your posts

. Lifted the screen: no change

. if I unplug my speakers from my ROLLS MX28 pre-amp (listening through headphones plugged on preamp): HUM STOPS

. if I unplug the power cable going to each speakers (they are powered: EVENT 20/20 bas): HUM STOPS

I am using unbalanced cables from my preamp to my speakers. I need to get the ROLLS preamp which converts to clean balanced outputs, and then use balanced cables (TSR jacks) to plug to my speakers.

I think this will fix my problem.

ronaldmeij · Post by **ronaldmeij** » Tue May 07, 2002 10:50 pm

Use a earthlift.

U have a groundhum , Check your powerconnections at the amp. maby try to plug the powerapm in a other socket or try to lift the earthshield for a minute from the poweramp to see if the hum is gone...

Its picking the hum by the audio cabling connected to the computer....

Post by **garyb** » Tue May 07, 2002 11:08 pm

the last post is likely the nail on the head.lifting the ground on the amp is fine.(leave the computer grounded tho!)

janila · Post by **janila** » Wed May 08, 2002 10:52 am

If you have everything plugged to the same grounded outlet there shouldn't be any grounding problems. If your monitor gets it's power from a different circuit than the audio equipment the voltage drop in the circuit will cause the grounding to balance the unbalanced situation thus causing hum if the monitor has a galvanic connection to the audio equipment. It obviously does through your computer. Therefore the hum stops when the current can't flow through the monitor. Get everything grounded. It should be that easy when you don't have any very long signal cables as you normally don't in a studio environment.

mano · Post by **mano** » Thu May 09, 2002 8:52 pm

ok more weirdness

now the hum doesnt go away, even when I turn off my screen or unplug my speakers (each used to stop the hum).

back to zero, so many problems!

ggrrrr

mano · Post by **mano** » Fri May 10, 2002 8:31 pm

OK fixed the problem! I plugged the screen and computer to the same power outlet and BOOM no more hum even when screen is on.

Well, I still have hums all over the place in my studio, but there are other reasons (found whats wrong, fixing it soon).

Kamurah · Post by **Kamurah** » Fri May 10, 2002 9:25 pm

mano...
Glad you found the culprit.

Grounding hums in studios can be a real problem.
Some quick things for all to consider:

1. Isolated transformers are your friend. However they are expensive. If you cannot afford...at least make sure you are regulating and filtering your power. APC or TRIPPLITE are good sources for both IPT's and regulated UPS.

2. Avoid multiple outlets. They may be tied to different transformers in your abode. Best to have everything coming off the same power line.

3. Racks. I love rackmounted stuff. But make sure you avoid the pitfalls associated with it. Get "spacers" (plastic washers that separate your gear from the rack rails) for all gear. Try to place an empty space between two modules. (I know this isn't always possible, but it helps separate the electromagnetic fields produced by the internal powe transformers in gear)

4. Use the BEST quality cables you can afford. It DOES make a difference, and it is easy to overlook. (I use either Monster or Mogami)

5. If you can, get an LCD monitor. It eliminates the magnetic fields produced by traditional CRT monitors.

6. If possible, have the power for your studio separated from your main power supply. I once operated in a studio that had the power on the same breaker as the fridge....it was God awful.

That's all I can think of off the top of my head....
I am sure some others can contribute...

Cheers

mano · Post by **mano** » Fri May 10, 2002 9:54 pm

kamurah great post man!

The reglated/filtered power outlet seems to be something I'll need to look into definitly! Any particular model to recommend? Those I looked at had 8 plugs and I bet they arent spaced enough to plug some of my big transformers (grr why are they always putting the big box at the end and not the middle?)

Kamurah · Post by **Kamurah** » Fri May 10, 2002 10:18 pm

Try these:

http://www.tripplite.com

or

http://www.apc.com/ww/index.cfm/

Cheers

<font size=-1>[ This Message was edited by: Kamurah on 2002-05-10 23:22 ]</font>

RedSun · Post by **RedSun** » Sat May 11, 2002 8:25 pm

If you want to reduce EM interference in your studio, the best solution is a LCD screen. It's also the most costly...

RedSun .:.