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Hello all,
Firstly, my gear for this issue
EOS Canon 70d DSLR
Rode VideoMicro
Neewer ac adapter

I have set up my camera to record myself talking.
The mic i've got is a consumer external mic, cost about £60.
Whilst using battery power with the camera all is fine, but if I use the AC adapter to power the camera, I get a loud powerline hum.
I've had a chat with a friend who works for Dynaudio and he confirmed that it was noise from the mains.

If I record using the camera's built in mic, no issue. I assume/guess that it is grounded properly.

What would be the fix for this?
I've heard of surge protecting extension cables that I can plug in the AC adapter, that have built in noise suppression but can only find them for EU plugs.

Would a better cable from camera to mic solve it?
Or perhaps AC adapter should be replaced with the Canon one (Neewer are a Chinese brand that are making a lot of camera gear for the vlogging community and it's cheap).

Or a better video microphone?

Thanks in advance if you have any thoughts.

Boswell Sat, 04/03/2021 - 04:15

Hi, and welcome!

This is almost certainly a problem with the use of that particular Neewer mains adaptor for powering the camera/microphone combination. That doesn't necessarily mean the adaptor is faulty, it may simply be unsuitable for this combination of gear. What is the model number of the Neewer adaptor?

It;s not clear from your post whether you get the hum if you externally power the camera while it's recording from its internal microphone, or only if you have the Rode plugged in and selected.

paulears Sat, 04/03/2021 - 05:00

DSLRs seem to be rather bad at this kind of thing. Unbalanced external inputs and lack of any real decent design in the circuitry. Also - they tend to squash everything as if there is a compressor. Dell laptops have been simply dreadful trying to attach external audio kit to for years and nobody is surprised. Hence why so many DSLR owners buy zoom recorders, I suspect.

Simeon54 Sat, 04/03/2021 - 06:29

Boswell, post: 468448, member: 29034 wrote:
Hi, and welcome!

This is almost certainly a problem with the use of that particular Neewer mains adaptor for powering the camera/microphone combination. That doesn't necessarily mean the adaptor is faulty, it may simply be unsuitable for this combination of gear. What is the model number of the Neewer adaptor?

It;s not clear from your post whether you get the hum if you externally power the camera while it's recording from its internal microphone, or only if you have the Rode plugged in and selected.

Thanks for the response.
Yes, using the external power supply and the built in mic works fine. My friend thought that was because the built in mic is properly earthed.

This is the model:
Neewer ACK-E6 AC Power Supply Adapter and DC Coupler[/HEADING]> 
It's very cheap, so i think i'm going to return it. I've found an official canon one on Ebay, and going to try get it. They're currently out of stock with Canon.

Simeon54 Sat, 04/03/2021 - 06:31

paulears, post: 468449, member: 47782 wrote:
DSLRs seem to be rather bad at this kind of thing. Unbalanced external inputs and lack of any real decent design in the circuitry. Also - they tend to squash everything as if there is a compressor. Dell laptops have been simply dreadful trying to attach external audio kit to for years and nobody is surprised. Hence why so many DSLR owners buy zoom recorders, I suspect.

Thanks for this. I do own a Zoom actually, but when i'm a one man show, it's a pain to have to set it up separately.
TBH, i'm probably over thinking it, I have 3 canon batteries, which is more than enough to deal with my needs.
I think, it's just one of those things that makes me want to fix it, even if there is a work around.

Boswell Sat, 04/03/2021 - 07:12

Just so I can get the full picture, this Neewer 8V power supply kit replaces the camera's battery, is that right?

What is odd about your hum problem is that the external microphone socket on the camera will have a separate regulator for generating the 3-5V needed for plug-in power, and this should produce smoothed d.c. whether the source is a real battery or a badly-smoothed battery substitute.

I guess if you are going to send it back we'll never know.

Paul999 Sat, 04/03/2021 - 07:43

I have my entire video system set up to run on Sony NP-F style batteries to avoid this problem. I haven't had the problem with video gear but when I am on location I do not want to be held hostage by power issues.

The problem could be the adaptor but it could also be your lighting interfering with power. If you are using proper video led lights you likely won't have the issue but if you are using a fluorescent kit of have any florescent bulbs on the same circuit the problem may persist even if you get a canon adaptor. I can run my Nikon z6 of of a 6600mah NP-F battery for about 6 hours continuous.

Simeon54 Sat, 04/03/2021 - 07:56

Boswell, post: 468452, member: 29034 wrote:
Just so I can get the full picture, this Neewer 8V power supply kit replaces the camera's battery, is that right?

What is odd about your hum problem is that the external microphone socket on the camera will have a separate regulator for generating the 3-5V needed for plug-in power, and this should produce smoothed d.c. whether the source is a real battery or a badly-smoothed battery substitute.

I guess if you are going to send it back we'll never know.

That does sound interesting. I am using LED lights, some plugged into the same extension cable that the power adapter is plugged into. Perhaps I should play with that, and see what happens if I plug it into it's own wall socket.

And yes, the adapter has a dummy battery 'head' that fits into the battery compartment.

Simeon54 Sat, 04/03/2021 - 07:57

Paul999, post: 468453, member: 42110 wrote:
I have my entire video system set up to run on Sony NP-F style batteries to avoid this problem. I haven't had the problem with video gear but when I am on location I do not want to be held hostage by power issues.

The problem could be the adaptor but it could also be your lighting interfering with power. If you are using proper video led lights you likely won't have the issue but if you are using a fluorescent kit of have any florescent bulbs on the same circuit the problem may persist even if you get a canon adaptor. I can run my Nikon z6 of of a 6600mah NP-F battery for about 6 hours continuous.

Yeah, I hear you. I have a couple of those batteries. But I'm already sick of keep track of which battery needs charging!
I do only use LED lights at present, but run off the mains..

Paul999 Sat, 04/03/2021 - 08:00

Simeon54, post: 468455, member: 52569 wrote:
Yeah, I hear you. I have a couple of those batteries. But I'm already sick of keep track of which battery needs charging!
I do only use LED lights at present, but run off the mains..

Try plugging in all your video equipment on its own circuit and lighting on another. Anything that is on the circuit can interfere. For testing make sure the circuit is as clean as possible.

paulears Sat, 04/03/2021 - 09:18

Before they invented switch mode power supplies - volts were just volts. Now they're remanufactured volts. In my office we have lots of Marine radio gear. Interference was a problem and I stuck an antenna into the analyser and from 156.2 through to 156.6 is a pyramid of noise products, making 156.4 the peak of the pyramid. Radios on marine channel 8 suffer the most - luckily there's not much there, but nearby there are some local users. Weak stations a way away are unreadable. Yesterday was a bank holiday and I was in the office and noticed hardly a thing on the analyser. Then at 10am it suddenly started and over five minutes built up. The office nearby where there are half a dozen people, with laptops, and all kinds of electrical wall-wart type power supplies. Chargers, printers, fans, computers, copiers, radios - all contributing a little to the noise that gets superimposed on the mains, and distributed. watching the screen you could almost see everything being turned on. Cameras just seem very unprotected, like some laptops. Many really hate being grounded accidentally by other equipment that has the screen connected to real earth - it provides an ideal path into their innards and they hate it!

Paul999 Sat, 04/03/2021 - 09:24

paulears, post: 468457, member: 47782 wrote:
Before they invented switch mode power supplies - volts were just volts. Now they're remanufactured volts. In my office we have lots of Marine radio gear. Interference was a problem and I stuck an antenna into the analyser and from 156.2 through to 156.6 is a pyramid of noise products, making 156.4 the peak of the pyramid. Radios on marine channel 8 suffer the most - luckily there's not much there, but nearby there are some local users. Weak stations a way away are unreadable. Yesterday was a bank holiday and I was in the office and noticed hardly a thing on the analyser. Then at 10am it suddenly started and over five minutes built up. The office nearby where there are half a dozen people, with laptops, and all kinds of electrical wall-wart type power supplies. Chargers, printers, fans, computers, copiers, radios - all contributing a little to the noise that gets superimposed on the mains, and distributed. watching the screen you could almost see everything being turned on. Cameras just seem very unprotected, like some laptops. Many really hate being grounded accidentally by other equipment that has the screen connected to real earth - it provides an ideal path into their innards and they hate it!

This type of knowledge is awesome.......and far above my pay grade:)

Simeon54 Sun, 04/04/2021 - 00:01

Thanks again for all this info and advice, I forgot how great forums can be. :-)

As an addition, I found this thread on a US based Canon forum addressing the same issue.
https://community.usa.canon.com/t5/EOS/AC-line-noise-on-mic/td-p/312452/page/2

The guy fixed it using a surge protecting extension cable with a noise filter built in.

Digital Energy EMI Sound Filter/Noise Reducer - 25 Foot Long 14/3 Cable - 6 Outlet Metal Body Surge Protector Power Strip | 1200 Joule, Heavy Duty Construction

Sadly, I'm in the UK and cannot find anything similar.

paulears Sun, 04/04/2021 - 01:18

The thing to remember is he didn’t fix it, he just prevented it cause the result. Let’s use an example. Your PC, full of circuit tracks carrying data, mostly 5volt square waves. Remember back to school physics. A flute is a sort of gentle sine wavey sound and a brass sound has a more sawtooth waveform and has sizzle and an edge. That’s the sharp edges of the waveform. Moog started making music with square waves and these have the highest number of harmonics because of the fast rising, sudden cutoff. Flutes get lost, a synth cuts through. Our computer has these harmonic rich voltages making it work. In the UK because of our 240v mains, we went through a time when we would earth everything for safety. Then we started just making things a bit better and brought in NO earthing. Ps US folk call this grounding, not earthing. So we have some kit designed not to have earths and other kit that needs it. That harmonically rich 5v mess is 5 volts relative to 0 volts, and all it takes is for some innocent bit of kit to join the 0 volt to earth. Maybe, on that one bit of kit, this makes it less noisy? A win? No! That is our shield on our audio cables, and we then feed it to the next bit of kit. Perhaps a mixer or interface. Maybe this too is happy, we then feed that to an amp or powered monitors and all hell breaks loose. Worst is nasty hums but more common are computery noises when we move the mouse, or use the hard drive. You can add new speakers, hear the noise and blame them, but the problem could be the power supply feeding your external hard drive, that has worked perfectly for five years!

some of those mains four way boards have devices to stop spikes in the mains. Some are one-shot devices. They sit there doing nothing, then a 300v spike comes along, and they grab it, prevent your kit dying, and then expire, having done their job just once. Some have the live, neutral and earth conductors wound through ferrite rings. The 50hz mains passes through, but higher frequencies get blocked - to a degree. Perhaps enough to stop the interference, perhaps not. You can even make better performing ones yourself if you have an old big loudspeaker laying around. dismantle them and remove the heavy large magnet. Pass your mains cable through it, or a mic cable or guitar cable and wind at least ten turns through and then tape up. They cost nothing and can/may/might help. The only downside is you will magnetise your screwdriver, and in the old days you had to keep them away from tapes! All that should go down you usb cables is data, but they’re a great way of spreading interference.

switch mode power supplies are small and efficient. To create the 5 or 12 volts they just chop up the mains and switch it on and off lots of times every second, then try to smooth it out. 240v square waves make for big harmonics. There are even regulations to prevent the noise escaping. Everyone ignores them. Clean and filtered power supplies are big and expensive. The ones we use everywhere cost less than a burger!

I have not come across a Dell computer that can be connected to a PA for years. Their power supplies are the cause. Run them on battery power and they’re actually nice sounding. Power them up and all hell breaks loose. They detect the power supply model, and prevent you using a non-authorised one. The power supply is clearly broadcasting what it is with superimposed data on the DC voltage. Is this the cause of the interference? I don’t know.