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Small live/party outdoors

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Re: Small live/party outdoors

Postby maryfallon » Mon Jul 16, 2018 8:39 pm

Hi Drew,
My laptop is connected with my external soundcard through a usb,the sound card through rca with the mixer and the mixer with the speakers through mono cable jacks to each one.Τhe power comes from different regular sockets to mixer and to the laptop.
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Re: Small live/party outdoors

Postby Sam Spoons » Mon Jul 16, 2018 11:47 pm

more specific info of what your rig is and what you are using it for (laptop for backing or for recording etc.)?
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Re: Small live/party outdoors

Postby maryfallon » Tue Jul 17, 2018 1:05 pm

Sam Spoons wrote:more specific info of what your rig is and what you are using it for (laptop for backing or for recording etc.)?


The rig is on the first post the (speakers and the mixer).What else do you want to know so i can tell you.(Laptop:Lenovo g500, soundcard:focusrite scarlett 2i2, mic 1:RODE SM6, mic 2:a cheap fame like sm58)The laptop is used to support soundcard so i can have phantom power for the RODE.I open the daw then 2 channels for each mic and thats it no vsts only some effect from the mixer.
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Re: Small live/party outdoors

Postby blinddrew » Tue Jul 17, 2018 1:53 pm

Hi Mary,
you might be best investing in a dedicated phantom power supply or a transformer isolator as it sounds like adding the laptop into the mix could be causing a ground loop. These can be tricky to pin down, but there are a couple of things to cover off first.
1, try to power all your equipment from the same socket. If everything is running off the same ground there can't be a loop...
2, what kind of cable are you using from the output of the focusrite to the mixer? Or are you taking audio output from the laptop?
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Re: Small live/party outdoors

Postby Hugh Robjohns » Tue Jul 17, 2018 2:32 pm

blinddrew wrote:If everything is running off the same ground there can't be a loop...

I'm afraid that's not quite right. There is still a loop -- just draw it out and it's obvious! -- but there is a benefit in running everything off the same socket which is that it minimises the size of the loop.

The nasty hum noises come from the voltage being developed between the mains grounds of the equipment, and that voltage being added to the wanted unbalanced audio signal which shares the same ground references, to create an audible hum.

The bigger the loop, the more cable is involved, and more cable means greater resistance. According to Mr Ohm, a current flowing through a higher resistance creates a larger voltage.

So, the smaller the loop, the smaller the voltage that develops across the mains earth cabling due to leakage currents, and that, in turn, reduces the strength and audibility of any ground loop hums added to the wanted audio signal.

Powering everything from the same mains socket (or double outlet) via a star-arrangement of plug boards doesn't remove ground loops, but it does minimise them and is therefore highly beneficial in most cases.

H
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Re: Small live/party outdoors

Postby Sam Spoons » Tue Jul 17, 2018 3:00 pm

Hi Mary, yes I did mean the PC/Soundard/mics. If it was me I'd buy a cheap soundhole pickup like the one I linked to above and us it and the SM58 clone for live. Keep the Rode for recording only. The SM6 is not the mic's type number but the shock mount, however it does tell me that the mic is a large diaphragm capacitor (NT2A?) and not ideally suited for live use.
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Re: Small live/party outdoors

Postby blinddrew » Tue Jul 17, 2018 3:19 pm

Hugh Robjohns wrote:
blinddrew wrote:If everything is running off the same ground there can't be a loop...

I'm afraid that's not quite right. There is still a loop -- just draw it out and it's obvious! -- but there is a benefit in running everything off the same socket which is that it minimises the size of the loop.
H
I stand corrected! :)
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Re: Small live/party outdoors

Postby Hugh Robjohns » Tue Jul 17, 2018 3:42 pm

blinddrew wrote:I stand corrected! :)

Right advice, but the wrong reasoning! :D
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Re: Small live/party outdoors

Postby blinddrew » Tue Jul 17, 2018 4:14 pm

I was trying to simplify but ended up overdoing it. :)

[EDIT] My thinking being that the PA was the only unit in there that was probably grounded (assuming the laptop has a class II power supply).
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Re: Small live/party outdoors

Postby maryfallon » Tue Jul 17, 2018 6:01 pm

I solved the problem with changing lenovo's adaptor after changing all the cables i finally figured it out!Thank you very much for your help guys!
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Re: Small live/party outdoors

Postby blinddrew » Tue Jul 17, 2018 8:57 pm

:thumbup: glad you got it sorted out, have a blast. :)
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Re: Small live/party outdoors

Postby blinddrew » Tue Jul 17, 2018 9:24 pm

Hi Hugh,
Mary appears to be cooking with gas now so please indulge me with a query. I'm assuming the PA is earthed, the 2i2 is bus-powered and the laptop is not earthed, so I'm struggling to see where the loop comes in?
What am I missing please?
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Re: Small live/party outdoors

Postby maryfallon » Wed Jul 18, 2018 2:20 am

I was wrong the other adaptor didn't fit well and the power came from the battery the whole time.So im in zero again!(the mic is NT1-A)I dont want to buy pickup for that cheap acoustic guitar that i have!
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Re: Small live/party outdoors

Postby Hugh Robjohns » Wed Jul 18, 2018 9:52 am

blinddrew wrote:I'm assuming the PA is earthed, the 2i2 is bus-powered and the laptop is not earthed, so I'm struggling to see where the loop comes in?

I suspect in this case the laptop supply is a grounded one, since the noise problem only occurs when the laptop is running on its mains supply, not on batteries.

I haven't been following the thread in detail, but I think I read that the output from the interface to the mixer/PA was on rca-phono leads. It's possible that simply switching those to TRS-TRS cables to run balanced would solve the problem -- assuming the powermixer has balanced line inputs (but I don't know if it has!).

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Re: Small live/party outdoors

Postby Sam Spoons » Wed Jul 18, 2018 10:08 am

maryfallon wrote:(the mic is NT1-A)I dont want to buy pickup for that cheap acoustic guitar that i have!

How are you getting on with levels on the guitar using the NT1A? And what is you reason for not wanting to buy a pickup?
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