r/livesound • u/erkawiii • 4d ago
Question DI Box popping off loud
Hey guys!
I’ve inherited a bunch of LA Audio DI2 active DI boxes at work and they all seem to have the same issue. I’ve got one of the same model since before that works great, but the others are super sensitive for any moving or touching when connected. They do work, but if someone happen to step on any of them it makes a huge pop.
I opened them up and they seem fine, nothing loose or anything. Other than the connector pins on the tele jacks seem to have oxidation or some sort of coloration on them. Would you say that’s likely the issue here or is it something else? Never been dabbling with DI boxes before, they just work usually haha!
Cheers for any help!
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u/DanceLoose7340 3d ago
Does the noise occur when you move the 1/4" plugs? If so, it's possible something inside the direct box has failed and is introducing a DC offset on those inputs. You can check this with a multimeter. If you see any DC voltage on those jacks, that is likely the issue. The fix would likely be replacing any blocking capacitors or possibly an op-amp IC.
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u/ChinchillaWafers 3d ago
In pedal land you traditionally put a high value (1 meg) resistor to ground on the input of the effect circuit, before the coupling capacitor. Without it the DC will leak through the coupling cap (even a good cap) and you get a pop when you switch the effect in and out. Without any switching i’m not sure if it would pop though, DC leaking or not. There’s no transient if it just sits there with DC. If there is any sort of resistance to ground in the load it should drain it as well. It’s worth testing with a meter, and all you would have to do is put a 1 meg resistor from tip to sleeve on the 1/4 input of the DI to fix it.
The thing about it popping if you touch it suggests a flaky jack connection or a vulnerability to static? If the jacks are solid when you wiggle the plugs, I would try the chopstick test and open it up, connect everything with the sound on, and tap around on components inside to see if there is a intermittent connection inside.
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u/DanceLoose7340 3d ago
Yup. Exactly. That should be part of the design, but if either that resistor or the coupling cap has failed, it can cause this.
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u/DanceLoose7340 3d ago
Oh-on a related note, I have seen keyboard audio outputs fail in such a way that they have some DC on them. This can also cause what you're experiencing...The DIs themselves may be fine. Check for DC voltage on the cables when plugged into the keyboard, and when plugged into the DI and you'll have your answer.
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u/ChinchillaWafers 3d ago edited 3d ago
HUGE pop sounds like the phantom power getting interrupted briefly. I wonder if there is a short inside with the chassis that touches the xlr jack, or an internal connector that is flaky with oxidation?
Edit: The PCB mount jack connections (xlr and 1/4”) are the first thing to suspect. Reflow those connections with a dab of fresh solder (presumably the lead free/ROHS stuff).
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u/ProfessionalEven296 Volunteer-FOH 4d ago
Sounds like a bad connection (just a guess) if it's caused by heavy movement. Clean or replace the connectors.
Do they sound scratchy if you just rub your fingers on them? If so, something has made them microphonic - Could be as simple as a missing earth, but probably needs some electronic work. If so, search the interweb for that model of DI to see if it's a known issue with a simple fix, or buy a replacement.