**** Issue of the Day ****
Look at that magnificent stage, look how open so bold. What could possibly be amiss? As I sit on the bus basking in the illusion of nothing to do for the moment, a PIN message comes through from Dave Lee "Need some help on stage." Grounding, buzz and humm issues can be some of the most illusive of the technical problems we encounter. So seemingly mysterious when everything is exactly the same and from nowhere, what was quite every day for a year, now sounds like a 40 foot mosquito somehow got inside. The issue today was real "stumper."
**** Imbedded Sound Nerd Speak ****
BRAAAAAAAAAAH! Really loud, near full guitar rig volume blares from JF's cabs with differing choices of worse available as the guitar is moved around the stage. Danny our tour electrician, has already checked all the stage and system grounding and using different power and metered everything. What is different? It effects the mainly the guitar rig while the bass rig only a little bit and the PA is quite. What is different, something must have changed. Each buzz, humm or rizz sounds unique in some way and there are two basic ways it infiltrates the audio, by wire or by air. I won't go into depth on it but as a rule of thumb, the best way to tell the difference is "if you physically move things around and it smoothly changes, it is in the air or more accurately, it is some sort of RF radiation. If the issue comes and goes as various things are plugged and unplugged, the issue is some sort of ground loop. Be sure to add the words "usually somewhat or probably."
Perhaps those mischievous lampi's have added a little monster to their rig? I asked that all the lighting and video power be shut down to eliminate it as a possible culprit, no change. I rechecked all the grounding and found that Danny the electric roadie, sure enough had everything is perfect in his world. Grounding stake to the stage, grounding stake at the generator as well as at the distro boxes, also grounding the stage there. AC neutral is bussed to ground at the generator, all good. Dave Lee, let me hear it again, click, BRAAAAAAAAAAH! Have you checked with the other bands to see if they have it?" Yes, they do too but not as loud, everyone has it a bit.
It is not the pedal board as it has been bypassed, it is not backline AC power and it makes no difference whether the guitar is wired or wireless,the noise it changes with the volume on the guitar. So I have Dave Lee walk the stage yet again, as the minutes till the first band tick away and doors have long since opened. It gets louder near the metal arch, so we add another ground stake to the stage and hear no change. "Can you set the guitar down and put a towel over the strings to stop it from the feeding back,? The small various and sounds of a Dave Lee roadie touching the guitar, masks any small change that may be useful to hear. BRAAAAAAAAAAH!
Set it down over there on the stage, and over there, and over there. Finally, good news and I have given you bloggery readers all the info you need to know the cause, have you figured it out? Go back to the first picture, what do you see?
Look - a stage, some seats, some sort of space needle thing that also just happens to broadcast all of the TV stations for the city. Hmmmm, well nothing suspicious here. Wait a minute, you are telling me that that is a high power RF broadcasting antenna just a block away, yikes, we don't want to be near that thing! Uh oh! Sit and think. Is the RF going straight from tower to the guitar pickups or is there another factor, the buzz drops when we it is farther from the stage metal. Sit and think. It has to be the stage itself, the stage is radiating RF and lots of it, massive amounts.
Perhaps the stage is acting like an antenna itself, resonating, re-radiating as it is immersed in the RF field. Well, the good news is I am pretty sure I know what the issue is. The bad news is that solving it may pose a bit of a problem. So the options appear to be:
A) Move the stage far away from the space needle of audio hate.
B) Persuade them to shut off TV for the city or
C) Figure out a way to ground the shit out of the stage in as many places as possible.
Ground the stage, lets take a look.
All wood pads, metal scaffold on wood pads, dry day. The stage is grounded but RF is a differing beast than 50/60hz AC. We need lots of grounds, 20, 30 or more would be good and that may, just may reduce the RF in their general area.
OK, I got it or at least an idea to keep us busy and and feel like an attempt was made and all I need is two cases of liter bottles of water and a big bag of salt. It is a long shot, never tried it before but it theoretically makes sense. We are going to use salt water to ground the stage.
On the second trip under the stage, I noticed that the whole front edge of the stage is sitting on wood pads atop huge aluminum plates atop what I am sure is nice damp grass. The aluminum plates should form a wonderful ground, all we need to do is establish a connection around the wood pad, salt water. I know I am going to take some heat for this request, none more deserving than I. "
"Production, um, this is Dave Rat and I am looking for...."
When it finally did show up in the hands of Roadie John, we headed down under and tossed little piles of salt on the legs and followed up with good splash of water. Ok, try it now, "mini-braaahhh"
Dave Lee smiles and says, I can live with that.
It appears to have worked but I am not fully convinced. Perhaps there were other factors. We did not do an immediate 'before and after' and an opening band and played between when we sought the salt and when we got it. Maybe the TV transmitter drops power at night, maybe the air temperature or some other seemingly unrelated factor changed or maybe the conclusion that it was the radio tower was wrong? Regardless, it works, it is better and the the next band plays.
"Dave Rat, they need you on stage." Aaargh. Way the heck over there, 15 mins till Peppers start and I can hear it already from front of house, BRAAAAAAAH! "It is not as bad as it was earlier but it is coming back." I asked Roadie George for a hand and we dragged a huge tub of water down front of the stage splashing water on the now dried salt as the water had evaporated But wait, the salt piles got bigger! Turns out roadie John had found more salt and re-piled all the legs, that was cool!
**** End Imbedded Sound Nerd Speak ****
"Hey Dave Lee, how is it now?"
"It's good again, thank you!"
**** End Issue of the Day ****
I listened to the guitar rig a few times during the show and the noise stayed low. I just wish I had the time to test it a few more times and be more sure that there were not other factors. If you are curious about the effectiveness of salt water as a conductor, here are a few links.