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winterbass

macrumors newbie
Original poster
Mar 17, 2020
3
1
Hi. I bought a Mac Pro 2019 for the studio and I have a problem like in the video. After turning on the Mac, the transformers in each studio device start working louder. On the recording, of course, the microphone stands very close to the housing with the transformer but this humming is heard in the place where I am sitting. You've got it in your Mac's too. Any idea what it could be and how to fix it?

 
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Macschrauber

macrumors 68000
Dec 27, 2015
1,566
631
Germany
Try another power source, if possible from another room with Extension Cable to see if its a humming loop.
 
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winterbass

macrumors newbie
Original poster
Mar 17, 2020
3
1
I tried. It is the same from all rooms. I also tried by Furman power conditioner. The same all the time...
 
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winterbass

macrumors newbie
Original poster
Mar 17, 2020
3
1
Thank you very much for your answer. I think this is situation no. 2. Booming does not come from the speaker but from the transformer amplifying this speaker. (These are active speakers) I have a UPS. When the Mac is isolated (ups is running on battery) the problem obviously disappears.
 
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DPUser

macrumors 6502a
Jan 17, 2012
955
241
Rancho Bohemia, California
I am thinking along the lines of #2 as well... almost seems as if, with the MP on, more current is being demanded than can be supplied, and the other transformers are making noise due to something akin to "clipping" of supply AC. A clipped waveform would tend to physically stress the transformers. I tried a little Googling but didn't turn up anything seemingly on-point.

I'd consult an electrician; if your power lines are overloaded or you have some loose connections, you could have a potential fire issue.
 
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IndioX

macrumors 6502a
Oct 1, 2018
857
359
austria/europe
this is not a problem with the power supply, but a ground loop that occurs over the wiring
keyword > earthing equipotential bonding
 
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codehead1

macrumors regular
Oct 31, 2011
108
92
Are you in the UK? That seems like 50 Hz...

As has been noted, this is a ground loop issue, the neutral or grounds are at different potential and you get current flow from one to another. Sometimes you can fix this by plugging things into the same outlet, power requirements permitting. You can also do things like lift audio grounds, but it's better to fix the underlying problem.

Wiring is almost always the issue. My home office/studio had it when I moved in, decades ago. I needed to remodel it anyway (it was a separate uninsulated building, only wood paneling on studs), so my electrician friend rewired, that was the end of the hum problem. There are extreme measures used by high-end studios for grounds, but this was simply pulling 10-gauge from the house to the studio to replace the existing crap, then probably 12-gauge for the internal wiring.
 
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DPUser

macrumors 6502a
Jan 17, 2012
955
241
Rancho Bohemia, California
It doesn't seem like a ground loop to me. As I understand it, the speaker is not amplifying a 50-60Hz hum, but it's transformer is physically producing the noise.

Booming does not come from the speaker but from the transformer amplifying this speaker.

If I am wrong, and the speaker is producing the sound thru its drivers, I will concur with ground loop diagnosis. If it is indeed transformers physically making the noise, I would find it hard to attribute the noise to a ground loop.
 
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worldvirus

macrumors newbie
Feb 17, 2016
19
31
Sometimes ground loops can be located by reversing the mains plug

This is pretty dodgy advice. ground loops generally occur when there are different distances to earth. star earth wiring in studio power points can help. lifting the earth in the audio line wiring rather than the power line can sometimes help too.
 
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codehead1

macrumors regular
Oct 31, 2011
108
92
It doesn't seem like a ground loop to me. As I understand it, the speaker is not amplifying a 50-60Hz hum, but it's transformer is physically producing the noise.
The original post is a little vague ("After turning on the Mac, the transformers in each studio device start working louder. On the recording, of course, the microphone stands very close to the housing with the transformer but this humming is heard in the place where I am sitting."—the first sentence sound like electrical hum, the second physical), but in later posts he seems to be clear it's electrical.

It's definitely 50 Hz, you can see the harmonics...

Screen Shot 2020-03-18 at 7.12.15 PM.png
 
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DPUser

macrumors 6502a
Jan 17, 2012
955
241
Rancho Bohemia, California
Has Winterbass left, now that spring has begun?

We may never know the truth.

I ran into a ground loop problem when certain Yamaha keyboards (Motif ES6 and S90ES) were connected by both Audio and USB (MIDI) cables to a Firewire interface-connected Power Mac G5 Quad. Lifting the AC ground didn't help, but cutting the USB ground worked wonders.
 
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