Microphonic Noise coming from axe

Keith White

Keith White

Experienced
so never had this problem before tonight. I bought a new rolling rack and from bottom to top this is the arrangement
1 presonus rm16ai rack mount mixer
2 axe fx 2
3 single space rack mount power conditioner
4 line 6 wireless rack

I am getting a microphonic sound and hum. And the gig starts in 30 minutes so i cant troubleshoot

Does anyone know which one would be causing the issue

Should i skip a space on any of them
 
keithguitarfan said:
so never had this problem before tonight. I bought a new rolling rack and from bottom to top this is the arrangement
1 presonus rm16ai rack mount mixer
2 axe fx 2
3 single space rack mount power conditioner
4 line 6 wireless rack

I am getting a microphonic sound and hum. And the gig starts in 30 minutes so i cant troubleshoot

Does anyone know which one would be causing the issue

Should i skip a space on any of them
Click to expand...
By the way when i bring the master volume down on the mixer the sound goes away so it isnt the mixer or the speakers. Dirty amp models have the hum clean do not but the gates have no effect on noise
 
My rig is Furman PL Plus DMC, AXE FX 2 XL Plus, Mesa Boogie 2:fifty. I play a certain outdoor concert a couple of times a year. I always get a hum and a gospel radio station. The only way to get rid of it and go totally silent is to lift the ground. While it's been mentioned it is not safe to do, my only choices are to lift the ground or be noisy and have a gospel station play every time I stop. It is the same sound company each time. I have complained that maybe they have a bad distro junction box, crossed neutral wire, ground loop or something. But they always put the blame back on me. Funny thing is, it is the only gig that has this problem.
 
Removing the ground can be hazardous... I would never take a chance so I can play, as I would be thinking if things went badly wrong then there may be people who have to pray.
 
You can put a DI box with ground lift switch between the effects processor and the amplifier.
It has a transformer inside so the ground loop will be broken.
 
Shenks said:
Removing the ground can be hazardous... I would never take a chance so I can play, as I would be thinking if things went badly wrong then there may be people who have to pray.
Click to expand...
Coming from old school, when there was no ground, we tend to not be afraid so much about it. And sometimes, in certain situations, being grounded can be just as hazardous as lifting the ground (the old hand on guitar, mouth on mic shock). I witnessed a player stuck one time, with his hand on his guitar and the other hand on the mic stand. He was grounded, but polarity was wrong. He could not let go.
For me it's "The show must go on". But to each their own.
 
Do you have your gear bolted directly to the rack rails? If so, most likely a ground loop. You should get yourself some Raxxess screws with a rubber washer (see pic), to isolate the screws from the rails. I use nylon washers in behind the rack ears as well, to isolate the gear from the rack.

Also, make sure each piece of rack gear doesn't touch the one above or below it. You can use thin foam pad to place in between each piece of gear, just be careful not to cover any vents.

Raxxess_PTSW_100_Phillips_Truss_10_32_x_143932.jpg
 
offrhodes said:
You can put a DI box with ground lift switch between the effects processor and the amplifier.
It has a transformer inside so the ground loop will be broken.
Click to expand...
In my case with the radio station and ground hum, DI boxes do very little. With the ground on it is really loud, with the ground switch lifted it is still loud. The ground lift on the back of the AXE does nothing as well. The only thing that makes it go away completely is the actual ground lift.
People would be surprised to find how many credible sound companies are lifting grounds on their power amps, effects processors, etc. sometimes it's the only way to get rid of bad noise. I'm not talking about regular ground loops or polarity. I'm talking about the really bad noise Here's one way to stop persistent guitar hum.
Figre3BBGuitars.jpg
 
Toopy14 said:
Do you have your gear bolted directly to the rack rails? If so, most likely a ground loop. You should get yourself some Raxxess screws with a rubber washer (see pic), to isolate the screws from the rails. I use nylon washers in behind the rack ears as well, to isolate the gear from the rack.

Also, make sure each piece of rack gear doesn't touch the one above or below it. You can use thin foam pad to place in between each piece of gear, just be careful not to cover any vents.

Raxxess_PTSW_100_Phillips_Truss_10_32_x_143932.jpg
Click to expand...
Unfortunately the minute you plug each piece of gear into the same power strip, regulator, conditioner, etc, it defeats your isolation. The chassis on each piece of gear is grounded to the ground of same. All my gear, in each rack, are grounded to the rack and the Furman, that is in each rack.
 
The gospel radio station might be a problem related to the venue, a nearby AM transmitter. They sometimes operate at crazy power levels and Megahertz frequencies, which may couple right across a DI box.
RF chokes might help, both in the power supply and on signal wires (see Fig 4 and 5 in [1]). The latter gets much more efficient when winding multiple turns, compared to simple clip-on chokes.

[1] http://audiosystemsgroup.com/RFI-Ham.pdf
 
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Tommy Tempest said:
In my case with the radio station and ground hum, DI boxes do very little. With the ground on it is really loud, with the ground switch lifted it is still loud. The ground lift on the back of the AXE does nothing as well. The only thing that makes it go away completely is the actual ground lift.
People would be surprised to find how many credible sound companies are lifting grounds on their power amps, effects processors, etc. sometimes it's the only way to get rid of bad noise. I'm not talking about regular ground loops or polarity. I'm talking about the really bad noise Here's one way to stop persistent guitar hum.
Figre3BBGuitars.jpg
Click to expand...


Um...

Really?

I'm not knocking if this works. But there has to be a more elegant way than roping yourself electronically to your setup to get rid of hum.
 
Tommy Tempest said:
I witnessed a player stuck one time, with his hand on his guitar and the other hand on the mic stand. He was grounded, but polarity was wrong. He could not let go.
Click to expand...
Polarity is a non-issue with modern power supplies—meaning anything legally manufactured in the last forty years or so—if the ground pin hasn't been defeated.

Ground doesn't have a polarity. If the player was getting zapped so hard that he couldn't let go, it means that someone—either the player or the venue—allowed power-line voltage onto something that should have been grounded. That can only happen when the ground has been broken/lifted. There is no reliable protection from that mistake.
 
It's right what @Tommy Tempest says - each to their own but I'll say it it again... for me I'd never want to put myself in a position where things could go badly wrong. I know we each have our own choices to make, but mine will definitely not include dodgy approaches nor workarounds towards electical safety.

Once, and only once, many years ago I received a zap whilst gigging and I promised myself it would never be repeated. It also seems odd that years ago it was almost an accepted part of being in the live (no pun intended) music scene but I've been around long enough to remember.

I now use a socket tester whenever gigging and if the electrical supply is suspect then the venue is informed and we cancel the gig. We also take steps to let any other bands/musicians scheduled to play there know the situation.
 
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Shocks across the chest, i.e. one arm or hand to the other, are said to be the most dangerous because your heart is in the current path. An old school rule of thumb is if you are going to test a possibly live wire or surface, you should do so with one hand in your pocket to avoid the cross chest path. If there is a shock, it would then most likely travel down to your feet and away from your heart.
 
mr_fender said:
Shocks across the chest, i.e. one arm or hand to the other, are said to be the most dangerous because your heart is in the current path. An old school rule of thumb is if you are going to test a possibly live wire or surface, you should do so with one hand in your pocket to avoid the cross chest path. If there is a shock, it would then most likely travel down to your feet and away from your heart.
Click to expand...


Always Use your right arm/hand. Your left arm has an artery that goes directly to your heart.
 
Not true. Arteries in both arms and hands branch from the heart pretty much equally. That's an old wives tale that folks spin about why people wear wedding rings on their left hands.
 
∞Fractals said:
Always Use your right arm/hand. Your left arm has an artery that goes directly to your heart.
Click to expand...
Both of your arms have arteries that go directly to your heart, as do both of your legs, your liver, your spleen, and your left nut (well, both of them, actually :)).


circulatorysystem.gif
 
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I'm sitting on the pot, trying to post the above on my iPad. Realize that IOS won't do an image URL copy. Finish my business. Jump on the real computer, and do my post. And what happens? @mr_fender jumps in ahead of me. :)
 
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