RF Interference - what can I do?

[buzzardwhiskey]

In prepping my system for this summer's gigs, I've noticed a troubling noise that I'm labeling as RF interference, but I'm actually not completely certain of its origin. It sounds vaguely "electric" or "intermittently buzzy" or "weirdly burbling".

My current system looks like this...

Martin CEO7 guitar
K&K pickup
Cable splitter box (signal A and B)
Signal A goes to Boss AD2 preamp
Signal B goes to ToneDexter preamp
Both signals go into Schertler Unico acoustic amp used as a stage monitor

I'm using pretty high grade cables, but I've switched them out looking for better with no luck.

Can anyone recommend a solution or a way to lessen the weird noises?

Thanks!

[Martin S]

Are any of your cables running close to a switch mode power supply? They can radiate a lot of noise that can get picked up in cables.

Cheap chinese power supplies are pretty bad for emissions as they don't include much filtering.

m.

[buzzardwhiskey]

I'm not very "up" on these things. I'm using a wall wart thingy called a "Trutone 1 Spot" that uses a string of power connectors. Could this be the culprit?

Maybe something like this would be better?

https://www.sweetwater.com/store/det...r-distribution

[srick]

Buzzard -

Here's your chance to play detective! The first step is to try and figure out where in the chain the interference is coming from. Or you could just put the whole thing together and start un-plugging (and re-plugging), one by one to see what part of the signal chain is causing the issue.

Start with the stage monitor and work backwards. IOW, Plug in the monitor - is there noise? If so, you know what you'll know where the problem lies. If not, then plug in the mixer, etc. etc. Re-create your whole signal chain until you find the component.

Ground loops that create interference can occur in power strips. Consider switching out the power strip. Also, try using more than one power strip and separate the pre-amp power supplies from the mixer supplies.

Sometimes, you can't figure it out and when you move the equipment to a different room, the interference is gone. Fluorescent lights, miscellaneous gadgets and computers are infamous for generating noise.

There's a lot of trial and error involved and no one answer for these issues. They can get pretty weird.

best,

Rick

[BT55]

Are you using a pedal power "chain" power supply cord. Those type of cords are notorious for introducing signal noise. Wall warts can do the same. I would try to swap out those items first.

[JohnDWilliams]

Plug the guitar directly into the amp. If you get buzz change the cable. If you still get buzz it's either the guitar or the amp. Swap each one out. Get the bad device repaired or shield it better.

If the guitar direct to the amp doesn't buzz start adding devices and cables into the chain, one at a time, until you get the buzz.

[buzzardwhiskey]

Thank you for all the help! I'm going to try a Strymon Ojai R30 power supply. It's slender enough to fit on the underside of my little pedalboard.

[lovgren]

I'm pretty sure it's the Tonedexter. The TD picks up a lot of RF noise. The solution is to ground it. However the only way to do that is via its XLR output.

Since I'm using 1/4" out from my TD, I have purchased a phantom power supply to connect to the TD XLR output for the sole purpose of providing a ground. Mine arrives Friday so I won't know if this works until then.

If you happen to have a mixer or powered speaker that takes an XLR input, you can plug that device into A/C power and then connect the TD to it and see if the noise goes away. In my case I used a QSC powered speaker. Poof, noise gone. Then you can develop a plan to ground the TD via the XLR output.

I'll post the results of my grounding experiment this weekend. The phantom power supply I chose costs $80. (annoying expense just to ground the TD) I plan to mount it under my pedalboard.

[Big Band Guitar]

Originally Posted by srick

Buzzard -

Here's your chance to play detective! The first step is to try and figure out where in the chain the interference is coming from. Or you could just put the whole thing together and start un-plugging (and re-plugging), one by one to see what part of the signal chain is causing the issue.

Start with the stage monitor and work backwards. IOW, Plug in the monitor - is there noise? If so, you know what you'll know where the problem lies. If not, then plug in the mixer, etc. etc. Re-create your whole signal chain until you find the component.

Ground loops that create interference can occur in power strips. Consider switching out the power strip. Also, try using more than one power strip and separate the pre-amp power supplies from the mixer supplies.

Sometimes, you can't figure it out and when you move the equipment to a different room, the interference is gone. Fluorescent lights, miscellaneous gadgets and computers are infamous for generating noise.

There's a lot of trial and error involved and no one answer for these issues. They can get pretty weird.

best,

Rick

This is basic troubleshooting. I have used the same basic steps for the 39 years I serviced industrial electronics.

The key is to change only 1 thing at a time.

[Big Band Guitar]

If it is determined that the noise is coming from the AC line, this should fix it.

https://www.tripplite.com/isolator-s...outlets~IS250/

Back when I was tracking down gremlins on power lines, I have measured very short duration spikes up to 14,000 volts on a 480 volt line. Yes I said fourteen thousand volts. 120 volt household voltage would have a lot more iron in the form of transformers between the 480 and 120 so any spikes that made it through would be a lot lower.

[MikeBmusic]

I have a pedal board with 2 power supplies - one for the Radial PZ Pre, 1 for the rest of the pedals, daisy chained. All was fine until I hooked up the Korg PitchBlack tuner pedal to the daisy chain power - BUZZ. taking it off the power and using a battery - no buzz.
So just experiment, one component at a time with your gear until you find the culprit.

[buzzardwhiskey]

Originally Posted by lovgren

I'm pretty sure it's the Tonedexter. The TD picks up a lot of RF noise. The solution is to ground it. However the only way to do that is via its XLR output.

Since I'm using 1/4" out from my TD, I have purchased a phantom power supply to connect to the TD XLR output for the sole purpose of providing a ground. Mine arrives Friday so I won't know if this works until then.

Lovgren is correct. It's the ToneDexter. I'll be interested in seeing if his experiment leads to fix.

[buzzardwhiskey]

Yay! I'm extremely happy. I figured out the problem and I think that the road I'm going to down will be a fix.

If I plug the ToneDexter and the Boss AD-2 into the same "string" of outlets hanging on a single iSpot, then the ToneDexter makes weird RF noises. But if instead, the two preamps use separate iSpots then no noise.

So I haven't yet received the Strymon Ojai R30 power supply but I'm hoping it'll be like using two separate iSpots.

[James May]

Originally Posted by lovgren

I'm pretty sure it's the Tonedexter. The TD picks up a lot of RF noise. The solution is to ground it. However the only way to do that is via its XLR output.

Since I'm using 1/4" out from my TD, I have purchased a phantom power supply to connect to the TD XLR output for the sole purpose of providing a ground. Mine arrives Friday so I won't know if this works until then.
...

A point of clarification here about grounding ToneDexter. You can do it either through the XLR or the 1/4" main output. The 1/4" output is always connected to TD system ground.

If you use both outputs, the XLR ground is disconnected. In other words, plugging in the 1/4" output opens the XLR ground to avoid ground loops.

[varmonter]

classic ground loop. glad you figured it out.
when you said RF i thought like "breaker one nine"
coming out of your speakers.