asdfghjkl GROUND LOOP

Discussion of music production, audio, equipment and any related topics, either with or without Ableton Live
funky shit
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asdfghjkl GROUND LOOP

Post by funky shit » Tue Jun 29, 2010 6:23 pm

damn moog pickin up a nasty ground loop noise.
ive used an extension cable from another loop (i think) for the moog and it has calm the buzz down a wee bit.
but its still awfull :( especially when i run it through a distortion unit.

any quick fix for this?
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luddy
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Re: asdfghjkl GROUND LOOP

Post by luddy » Tue Jun 29, 2010 6:39 pm

hi,

Is the unit grounded (i.e., has a three-prong plug)? Sometimes hum builds up in the case of the unit if it doesn't have a solid connection to ground.

If it has balanced outputs, using a balanced cable (TRS) might help eliminate any hum that's getting into the cable...

-Luddy

Tone Deft
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Re: asdfghjkl GROUND LOOP

Post by Tone Deft » Tue Jun 29, 2010 7:24 pm

check your 'movie' thread. :roll:

(you almost answered your own question, good luck.)
In my life
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At people who I'd much rather kick in the eye?
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funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Tue Jun 29, 2010 9:55 pm

luddy wrote:hi,

Is the unit grounded (i.e., has a three-prong plug)? Sometimes hum builds up in the case of the unit if it doesn't have a solid connection to ground.

If it has balanced outputs, using a balanced cable (TRS) might help eliminate any hum that's getting into the cable...

-Luddy
it is grounded, and using balance cables yes.
Tone Deft wrote:check your 'movie' thread. :roll:

(you almost answered your own question, good luck.)
??????????????
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bassistheplace
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Re: asdfghjkl GROUND LOOP

Post by bassistheplace » Tue Jun 29, 2010 10:19 pm

Check any digital cables you are using. (USB, MIDI)

luddy
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Re: asdfghjkl GROUND LOOP

Post by luddy » Wed Jun 30, 2010 12:35 am

Well, if it's grounded and using balanced cables then it might well be a bonafide ground loop, which is just a fancy way of saying that the grounds of one or more pieces of equipment that are plugged into one another are not at the same voltage.

The usual first remedy for this is to lift the ground on one end or the other of the balanced cable that is connecting it to the other gear. A typical balanced cable has the shield connected to pin 1 at both ends of the cable. You can create a ground lift cable by breaking the pin 1 connection at one end -- maybe try at the Moog end of the cable first. On a TRS cable, pin 1 is the 'S' (shield).

hth,

-Luddy

funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Wed Jun 30, 2010 1:25 am

luddy wrote:Well, if it's grounded and using balanced cables then it might well be a bonafide ground loop, which is just a fancy way of saying that the grounds of one or more pieces of equipment that are plugged into one another are not at the same voltage.

The usual first remedy for this is to lift the ground on one end or the other of the balanced cable that is connecting it to the other gear. A typical balanced cable has the shield connected to pin 1 at both ends of the cable. You can create a ground lift cable by breaking the pin 1 connection at one end -- maybe try at the Moog end of the cable first. On a TRS cable, pin 1 is the 'S' (shield).

hth,

-Luddy
i think its my firewire mixer causing the problem then, as it my monitors give a hum aswell when the firewire cable is plugged in.
should i remove the ground pin on the mixer?
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Re: asdfghjkl GROUND LOOP

Post by luddy » Wed Jun 30, 2010 1:58 am

Computers and digital gear often create this kind of problem because they have very noisy power supplies and throw off a lot of high frequency energy. Something like your mixer, that has both digital connections and analog ones, is begging for this kind of problem. A bunch of junk travels from the computer to the mixer over the shield of the firewire cable and from there gets into your analog gear over their shields.

First, make sure both mixer and computer are properly grounded, i.e., that their power cords have ground pins and you are convinced they are making good contact. They're probably already grounded though.

The best solution would probably be to electrically isolate the computer from the mixer. If you can get some kind of firewire isolator (I think there are various kinds of these, some repeaters, some simple coupling devices), and insert it between computer and mixer, it would probably help a bunch.

Otherwise, I think I'd try to make a single ground-lifted TRS cable (with pin 1 connected to the shield at one end, but with pin 1 disconnected at the other), and try inserting it here and there in your setup (try putting the ground lifted plug at the mixer end first), to see what happens to the noise.

If you can electrically isolate the computer from the mixer, it's better than ground-lifting the analog connections, because your mixer is full of that high frequency junk coming from the computer, and it would really be best to get rid of that if possible, rather than to simply stop it from spreading.

good luck,

-Luddy

funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Wed Jun 30, 2010 2:07 am

cheers everyone.
my think that the extension chord im using the moog on is on a different loop. ill try pluging the mixer into it instead.
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funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Wed Jun 30, 2010 2:14 am

funky shit wrote:cheers everyone.
my think that the extension chord im using the moog on is on a different loop. ill try pluging the mixer into it instead.
= fail.

will try this with the computer instead (monitor & desktop) on the outside loop.

grrrrrrrrrrrrrrrrrrrrrrrrrr :x
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Tone Deft
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Re: asdfghjkl GROUND LOOP

Post by Tone Deft » Wed Jun 30, 2010 2:37 am

could be LOTS of things...

noise can be radiated through the air (radiated emissions) or conducted through wires (conducted emissions.)

for radiated emissions try turning of electronics around the room, one at a time and listen for the noise. anything from lights to a TV, a fan to another synth. it's also possible that simply rotating gear can change the effect of the radiating noise. have you ever looked at an LCD display with polarized sun glasses on and you can't read it until you tilt your head? that's polarization, same thing works for radiated electronic noises. (maybe I'm off on a tangent here)

for conducted emissions, as you mentioned you want everything to be on the same circuit breaker. cutting the third prong on electronics can help eliminate this path.

it could even be something in another room. long ago a forumite had monitor noise, after many back and forths we deduced that it was a the freaking air conditioner on the top of his building that was doing it. that and his monitors were supposed to be shielded but they weren't.

also, ALWAYS be suspicious of your wiring. we all like to use the same cables over and over again, over time the wear from coiling and uncoiling can make the trusty old cable a worthless POS. add to that the wear from plugging and unplugging cables.

it's also possible that the patch you're working with has a really low output and you're cranking the synth really loud and hearing the noise floor that you didn't notice before.

LOTS of things can go wrong, be thankful when they're not. ;)


movies? music oriented ones a bit off the beaten path...
To All The Mornings Of The World (it's a French film, that's the English title, too lazy to look it up.)
The Legend Of 1900
Thirty Two Short Films About Glenn Gould
The Red Violin

TBH I haven't seen the last two, I was just talking with some coworkers about cool music movies that aren't the typical flicks.
In my life
Why do I smile
At people who I'd much rather kick in the eye?
-Moz

funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Wed Jun 30, 2010 3:09 am

nice ^


right well its definatly not the noise floor. definatly not the cables. im not even in a house :lol: (garage)

about the monitors buzz - if i remove the firewire cable from the mixer, the buzz goes away. if i do something different on the computer, it might change frequency. for example.. open a website which runs flash, or open up ableton.

also: tried the moog thru the mixer without the cables plugged in. sounds like that hum you get from a guitar amp.
maby its just the moog?

i can live with the monitors being like this because its not on the recording path.

also: cheers :)
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Tone Deft
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Re: asdfghjkl GROUND LOOP

Post by Tone Deft » Wed Jun 30, 2010 4:20 am

I assume the mixer has a grounding lug used for turntables? try attaching a piece of wire to that then touching that wire to the bare metal casing (the unpainted, non-anodized parts) of various bits of gear.


if i do something different on the computer, it might change frequency.
yeah, that's just crap from the computer, damn things aren't always designed with audio in mind.


tried the moog thru the mixer without the cables plugged in. sounds like that hum you get from a guitar amp.
that sound is the mains voltage (the power in the walls of the garage) leaking into the system (conduction.) that would be an issue with grounding lugs on bits of gear or simply having a gain stage of your setup cranked too high. that sound is pretty much everywhere, it's just usually REALLY low.
In my life
Why do I smile
At people who I'd much rather kick in the eye?
-Moz

funky shit
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Re: asdfghjkl GROUND LOOP

Post by funky shit » Wed Jun 30, 2010 4:27 am

Tone Deft wrote:I assume the mixer has a grounding lug used for turntables? try attaching a piece of wire to that then touching that wire to the bare metal casing (the unpainted, non-anodized parts) of various bits of gear.
The mixer isn't one for mixing. if you know what i mean.. :lol: (not a dj mixer)
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Tone Deft
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Re: asdfghjkl GROUND LOOP

Post by Tone Deft » Wed Jun 30, 2010 5:19 am

ahh cool.

still, the same concept applies. you can diagnose ground loops by taking a length of wire and touching the case of one device to another. when the buzz goes away then you know which bits of gear aren't playing together nicely. just be sure you're actually touching the metal casing, without paint, anodizing and all that.
In my life
Why do I smile
At people who I'd much rather kick in the eye?
-Moz

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