If you want to prevent -or are trying to eliminate- acoustical or visual intereferences, “hum”, ground loops… make sure all your devices (and any devices electrically connected to them in any way) are powered by the same power line.
For example, our live shows support music events and are sound-reactive. So there always will be at least one audio cable that connects our video equipment to the audio mixer being used by DJs or musicians. To prevent ground loops, we put all our equipment -including projectors and TVs- on the same power line as the musicians.
In our experience, event promoters and venue technicians or owners will assume video equipment should go on the same power lines as lights.
If you connect to their sound system, you may have to explain why this is not the case. We never had to say more than “we know this is the way to go to prevent ground loops” but YMMV.
Also this will likely require some additional resources (extension cords and/or power strips, basic knowledge), additional time and possibly some planning (especially if other artists are involved in the same event) so take that into account: DIY (do it yourself) or put it in your tech rider and make sure they care about it.
We empirically verified this approach in a music club that has a very good sound system and an electric system correctly set up. We had connected the projector to our equipment, and we had powered it up from a separate power line. The sound system was emitting a noticeable (and unacceptable) “hum” noise, which disappeared as soon as we put the projector on the same power line as our equipment.
We have been following the same approach since, in at least 4 other different music venues and we never had issues so far
i just ran in to this today actually! it’s a tricky one though because our stuff is running off of generators, and it’s not always possible for the video stuff to be wired to the audio stuff directly. gunna be grabbing a ground loop isolator for our next event.
Reviving this thread with one slight clarifying question about using ground loop eliminators/isolators to tackle this type of problem, since there are a lot of options out there. Are all isolators created equal in terms of their application to both audio and video signals? Put another way: Will a RCA ground loop isolator marketed for audio still sufficiently eliminate hum for composite video? From my searching it seems like units labeled for audio (e.g., car/home stereo applications) are typically smaller, cheaper and more widely available than video ones (e.g., for avionics, boating, medical equipment etc). Any important differences that should be kept in mind when comparing the two?
the short answer is no, if noise is an unavoidable issue with yr set up (i.e you have roland gear, small tft monitors, and/or VSERPI stuff in the chain) and you absolutely require crystal clear analog video, you should definitely purchase a Video ground loop isolator and probably consider buying something that isn’t the cheapest option. poor quality can affect video signals in a different way from the good old scrolling 60hz noise oscillator. on the other hand you could load up on a bunch of cheap ones see how weird you can make things!
the longer answer is that cheap ground loop isolators for audio can have issues with unstable frequency response for audio signals. nicer audio ones will be well designed to preserve everything in the normal audio range, which doesn’t really say anything about how they will behave with a composite video signal. again, could be fun to experiment with them as a glitching device but could just be expensive, time consuming, and frustrating if yr main goal is just eliminating noise.
nope, the professional & long range alternative to CVBS is just SDI for broadcast/television and/or LAN VOIP for everyone else. both of these would be silly to implement for most folks interested in analog video art stuff. analog video is very much a ‘warts and all’ situation.
we never had issues so far