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Grounding loop hum in studio

 
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neytal



Joined: 02 May 2012
Posts: 7
Location: Bohemia

PostPosted: Thu May 03, 2012 11:38 pm    Post subject: Grounding loop hum in studio Reply with quote

Hi all,
I was just wondering if is it just me or this is popular problem. I hate to say but I have no idea how to fix grounding loop hum in my `studio`. I got Soundcraft Spirit 16 Chanel (old but i love that mix) witch makes no hum at all while is no inputs connected in. Than i use Korg EMX and Korg ESX as a synth module and sampling drum machine, both of them controlled from Ableton thru M audio Fast Track witch i cant complain about except the hum what i makes while its connected to my desktop computer, If i don't use desktop computer but notebook without grounding spike on adapter there is no hum, but its not solving my problem, i would like to use my desktop mac with goes sweet with ableton with no lags. I found Grounding loop isolators witch u plug between sound card and mix, but than the hum comes from the Korgs and Quadraverb what are connected to sound card by midi cables. I wonder if there is any solution of my problem, like box where i plug all my equipment i use in studio and it will solve the differences in grounding, or something i could put i between computer and external sound card witch are connected bu usb cable, or so...

Thank you for suggestion and time u spent on reading this grammar less question.
Thank you

_________________
Using Ableton Live, recording by midi keyboard Roland Edirol, using live bass guitar, melodica.
I own Soundcraft Spirit Studio 16 Chanel mix and effects sotcha Zoom reverbs, Alesis Midiverb, half rack Boss Delays and Vintage time machine
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interruptor



Joined: 04 Sep 2005
Posts: 1138
Location: Switzerland

PostPosted: Fri May 04, 2012 9:19 am    Post subject: Reply with quote

Did you look already at your power supply connections? Sometimes hum problems can be cured by making sure all devices are connected to the ac power at the same wall outlet. Avoid connecting them to ac power in different rooms.
Hum can also be picked up by signal cables with bad shielding, particularly if they are located close to ac power cables.
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neytal



Joined: 02 May 2012
Posts: 7
Location: Bohemia

PostPosted: Sat May 05, 2012 9:07 am    Post subject: Reply with quote

hi,
thanks for reply. I actually did try to reconnect all of it to same outlet, i did run extension cord from different branch (next flat) and combine the connecting to different outlets it didnt change a bit. about bad shielding of cables, it might be possible with my mixing desk power supply, its kind of old school and you can see that somebody already changed the cable from PSU to mixin desk. but even everything is pluged into outlet and running without connecting each other there is no hum until i connect them into each other. than i see little spark and hum begins. do you thing that i should get grounding loop isolator to every single channel on mix even sends? its bit over my buget, Smile but still better than the hum, its awful man. you can hear it on most of my records. makes me not want to record any more

http://soundcloud.com/search?q[fulltext]=iya+iration

_________________
Using Ableton Live, recording by midi keyboard Roland Edirol, using live bass guitar, melodica.
I own Soundcraft Spirit Studio 16 Chanel mix and effects sotcha Zoom reverbs, Alesis Midiverb, half rack Boss Delays and Vintage time machine
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interruptor



Joined: 04 Sep 2005
Posts: 1138
Location: Switzerland

PostPosted: Sat May 05, 2012 12:54 pm    Post subject: Reply with quote

You mentioned that you got it working using grounding loop isolators on your soundcard connections. Only the midi connections seem to cause a loop again. This is odd because midi interfaces incorporate opto couples to prevent hum problems (see this http://en.wikipedia.org/wiki/MIDI_1.0).
You should first check your midi cables as proposed in this article here:
http://www.soundonsound.com/sos/jun02/articles/pcmusician0602.asp (see blue box titled "midi leads")

As midi relies on the transmission of a modulated current using two wires (pin 4 and 5 on the connector) there is no need for a ground connection. I understand transmission should work even if only pin 4 and 5 are connected.
See this example of a midi interface schematic:
http://fr.audiofanzine.com/dossiers_v3/intermidi/cablemidi.htm
Only two lines are used from the "IN" port which are driving the LED of an opto couple. If only these two are connected there is no way hum can occur!

I think your problem should be solvable without shelling out more money on hum isolators..
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neytal



Joined: 02 May 2012
Posts: 7
Location: Bohemia

PostPosted: Sat May 05, 2012 4:45 pm    Post subject: Reply with quote

Smile wow, i never thought about the midi cable. i am sure it is it. thank you very much. i am gonna fix my midi cable what goes from sound card out and let you if it works. jah bless you good man, thank you
_________________
Using Ableton Live, recording by midi keyboard Roland Edirol, using live bass guitar, melodica.
I own Soundcraft Spirit Studio 16 Chanel mix and effects sotcha Zoom reverbs, Alesis Midiverb, half rack Boss Delays and Vintage time machine
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noiseboy



Joined: 16 Mar 2010
Posts: 30
Location: Glastonbury country

PostPosted: Thu May 10, 2012 10:46 am    Post subject: Grounding loop hum in studio Reply with quote

If the problem is an earthing potential difference then ensuring all of your equipment is grounded and to the same point should stop the hum. As Interruptor said, midi is opto-isolated so shouldn't be able to create an electrical connection between two devices either with different, or similar, ground potentials.
The fact that you are getting a spark when connecting devices suggests you have a floating ground somewhere in your set-up. Unplugging a cable may well stop the hum but you won't have fixed the cause of the problem. At least one of your devices will have a measurable voltage above zero at its earth rail where ideally all devices should be the same and as close to zero as possible. Something may have a faulty power supply. Computer PSU's very often cause earth potential problems in an audio set-up and it sounds like that may be at the root of the problem. You could try a different known good desktop computer (maybe a friends Mac e.g.) to test this.
Maybe get an electrician friend to check your set-up out to find the device with the problem? If it's a bad problem, left unchecked it may cause further damage to other devices.
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neytal



Joined: 02 May 2012
Posts: 7
Location: Bohemia

PostPosted: Mon Feb 25, 2013 8:05 pm    Post subject: Fix Reply with quote

Hi there, i just would like to thank you. I couldn't fix it and i did not find anyone to measure my computer power supply. Well, the thing got fixed after i bought new new sound card, witch is MOTU MKII 828 whit its own cable to outlet. The old-one had just usb cable so it was not in the same circuit as the rest of things. I got rid of Korg ESX and korg emx (too much fun on its own to sell) with mix and computer does not hum at all. I don t know what actually did fix it but i believe that it was the MOTU with its own juice feeding. What i know is that my sound is finnaly clear with no hum, even i am using old kit.

https://soundcloud.com/neytal/prc-ynk

Anyway thanks and big up

_________________
Using Ableton Live, recording by midi keyboard Roland Edirol, using live bass guitar, melodica.
I own Soundcraft Spirit Studio 16 Chanel mix and effects sotcha Zoom reverbs, Alesis Midiverb, half rack Boss Delays and Vintage time machine
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View user's profile Send private message Visit poster's website
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