ground loop isolator

[Steve Eisen]

Humbucker

Steve Eisen
Eisen Video Productions
Board of Directors
Chicago Final Cut Pro Users Group

[Tom Matthies]

They’re made by ADC. A quick Google and they are $165 from Markertek.
Tom

Life moves pretty fast. If you don’t stop and look around once in a while, you could miss it.–Ferris Bueller

[Chris Borjis]

thanks guys.

I bought one that was in-line with bnc connectors and it didn’t work at all, but
it was a much cheaper one.

[Thaxter Clavemarlton]

Humbuckers have worked for us.

[Bob Zelin]

these are all bad recommendations. Humbuckers from ADC, Allen Avionics, Jensen Transformers, etc. are all band-aids, and are designed for “remote truck” jobs, where you don’t have time to fix the problem.

You have a simple electrical grounding problem. This means that you have two rooms, or one big room, and the electrical grounds are not going back to the same panel. This creates a “ground potential” (a voltage between the grounds), and you get hum. A video signal is only 700 millivolts, so even a tiny amount of AC ground potential will cause hum in your system – both video (rolling bars in your picture), and audio hum.

You MUST hire an electrician to correct this problem. He must run your electrical outlets back to the same panel, where all the “lows” (the white wire) are all tied to the same buss bar, and all the grounds (green wire) are all tied to the same ground. If you have an AC extention cord, and a cheap voltmeter, you can actually measure the AC voltage between the two grounds that you have plugged in.

You can temporarily solve this hum problem by getting a cheap 50′ AC extention cord, and some cheap AC outlet strips, and plug ALL of your equipment into ONE ac outlet on your wall. So if you have 2 rooms, make sure that nothing is plugged into the wall outlets of one room. Now, you will get no hum.

Bob Zelin

[Rennie Klymyk]

Thanks for the great post Bob! I think my building is older than electricity so I kinda thought I was hooped for an easy fix to my similar problems.

“thou can not stir a flower without crumbling a star” ……Henry Wadsworth Longfellow

[Chris Borjis]

Thanks Bob,

I was hoping you would chime in.

I’m perplexed why the ground isn’t good in my building.
It’s a state-of-the-art facility where no expense was spared
when it was built for video post some years back by a former tenant.

Millions were spent and yet we have audio and video ground loops….which frustrates us all here.

fortunately it doesn’t happen over SDI but the few occasions I need
3/4 or D2 from the machine room, I get the video rolls.

I thought a box might be less than an SDI converter to solve the problem.

I like your idea of an extension chord on the same power, but If I just use
the UPS in the machine room that powers our equipment in the video suite across
the hall I would assume that would solve it as well (being the same power source)

[Tim Kolb]

In a new building, ground loops are kind of inexcusable…

I used to work for an institution with a studio and suddenly one day we had interference that seemed to manifest itself as ground loops all over the place. They went as far as drilling down through the concrete base of the building and driving a freaking copper rod 7 feet into the ground…still had issues.

They finally found a fluorescent light fixture in a near by rest room that had gotten a defective ballast changed and was configured improperly. AC problems gone.

All told, I suspect that was the most expensive light ballast ever installed…

BTW…I think Humbuckers are OK…I’ve had mixed results. I’ve done a lot of large conference staging jobs where we simply scouted the power ahead of time and brought or bought adequate AC cabling to route it properly.

TimK,
Director, Consultant
Kolb Productions,

[Chris Borjis]

[Tim Kolb] “In a new building, ground loops are kind of inexcusable…”

Tell me about it Tim! 🙂

when we first moved in to this facility I was quite relieved to see all the copper ground strips in the data center and various studios.

Our old facility had isolation transformers all over the darn place due to the problems we had there.

they are not quite as bad at the new place, but definitely here in a few places.