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SD 302 Phantom Power Crackling Sounds


Sean ONeil

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Howdy Folks,

During a shoot I heard some strange crackling noises while using my Schoeps CMC 6/41microphone and powering it through my 302 Mixer, using Nickel Metal Hydride, Energizer 2500 MaH AA rechargeables.  Thinking it was a bad cable, I swapped out my cables, and the noises remained.  I then tried my other two inputs, the noises remained.  Thinking it was my Schoeps crapping out, I swapped out to my Neuman KM 100, and still the noises remained.  I then switched to a T powered Sennheiser 416, and the problem went away.

I sent the 302 to Sound Devices for servicing.  They replaced 3 XLR inputs, 3 fader pots, both return pots, battery cap, updated to firmware 3.06, and a few other things. They never got the unit to make the same noises on the bench and it passed all of their bench tests.  They said the Phantom powering looked good on all three inputs, and sent it back to me.

After shooting with it for four straight days, it was fine until the same problem, but more intense reoccured. The 302 is now back at Sound Devices. They want to give me a new battery spring, and feel the issue might be with using rechargeables.  The Sound Device tech suggested I should use Duracell alkalines instead. I told him that was not an option and that I know a dozen people using ONLY Nickel Metal Hydride's.

Has anyone else had this problem?  There is a suspicion that the problem is in using Nickel Metal Hydride rechargeable batteries.  I've been using them for 6 years in this same exact configuration without a problem.

Any ideas out there?

Cheers,

Sean O'Neil

Brooklyn NY

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I've had the phantom "crackle" too, on both the 302 and 442. Tried the obvious solutions, swapping cables, mics and channels. In the end, I used a short (about 30cm) header cable between the mixer and boom cable.

This solved the problem. It took away any pressure or strain from the input on the mixer.

I think part of the problem is the constant strain on the input. Placing the header cable in between eliminates this strain.

It's not a problem with inputs from radio mics since there's no strain or movement plus the fact that those inputs are usually at line level or dynamic.

I use the header cable on my 552 and 788C/L8 and have never had the crackle.

Also make sure the cables have pin 1 jumpered to the shell of the XLR

Cheers

Peter Mega

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Why would trying a different battery type not be an option?? 

That would be the first thing I would try.  Also, I agree with the previous posts that suggest you look closer at your signal flow through each cable. Check all connectors, etc..  After months of use the connector on one of my boom cables tends to oxidize a bit and start to crackle when strained (right angle XLR female that connects to butt of pole, most exposed to the elements).  A little tuner cleaner, or deoxit usually clears it up.  If it continues to be a problem I cut it off and install a new connector.

Keep in mind that the NiMH AA has significantly less voltage (1.2V per cell as opposed to 1.5V with Alk, and almost 1.8V with a fresh Lithium AA).  The possibility of the 302, or maybe even yours in particular (component variation), not taking well to the lower voltage seems likely.  I have some transmitters that exhibit strange behavior and distortion when powered with NiMH AAs.

I tend to just use lithiums these days to avoid this kind of random behavior.  Too much else to worry about, and it's an easy fix.  A little more $$ but for me it's worth it.

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I was getting some random crackling on my boom and it seemed to be coming from the right angle connector plugged into the bottom of the boom pole.  Other times it seemed to be where it went into the mixer.  Strain reliefed it better and it seemed better.  Always the problem kept coming back.  This was with both a 302 and a 442 with an external central battery.  Then I put a 48 volt power supply in line and I thought the problem was solved.  It still cropped up now and again especially when touching the right angle connector.

I then noticed that the rubber o ring on the connector was quite compressed  and worn.  I replaced it with a new silicone o ring that was nice and fat.  Problem solved for good.  No more noise no matter what.

Bernie

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I had crackling on my mixpre before. It turned out to be the headphone potentiometer.

A little DeOxit Gold fixed the problem.

Howdy Folks,

During a shoot I heard some strange crackling noises while using my Schoeps CMC 6/41microphone and powering it through my 302 Mixer, using Nickel Metal Hydride, Energizer 2500 MaH AA rechargeables.  Thinking it was a bad cable, I swapped out my cables, and the noises remained.  I then tried my other two inputs, the noises remained.  Thinking it was my Schoeps crapping out, I swapped out to my Neuman KM 100, and still the noises remained.  I then switched to a T powered Sennheiser 416, and the problem went away.

I sent the 302 to Sound Devices for servicing.  They replaced 3 XLR inputs, 3 fader pots, both return pots, battery cap, updated to firmware 3.06, and a few other things. They never got the unit to make the same noises on the bench and it passed all of their bench tests.  They said the Phantom powering looked good on all three inputs, and sent it back to me.

After shooting with it for four straight days, it was fine until the same problem, but more intense reoccured. The 302 is now back at Sound Devices. They want to give me a new battery spring, and feel the issue might be with using rechargeables.  The Sound Device tech suggested I should use Duracell alkalines instead. I told him that was not an option and that I know a dozen people using ONLY Nickel Metal Hydride's.

Has anyone else had this problem?  There is a suspicion that the problem is in using Nickel Metal Hydride rechargeable batteries.  I've been using them for 6 years in this same exact configuration without a problem.

Any ideas out there?

Cheers,

Sean O'Neil

Brooklyn NY

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Hi Rasmus,

Sound Devices wants to send me my mixer back saying it's OK now.  Here's what they did the second time 'round:

Repair:- Changed contact spring in battery tube to new style for more reliable contact with rechargeable batteries.

- v3.06 Passed test.

- Replaced all small parts in 48V Phantom supply circuit.

- Passes factory bench test.

Although I trust,respect, and am an official Kool Aid drinking member of Cult Sound Devices, I'm not totally convinced the new "contact spring" is the answer to my dreams like the tech on the phone suggested.  Also, it's not clear to me why they didn't replace the "small parts" in the 48v Phantom supply circuit the first time I sent it in for repair, instead of sending it back and breaking down on me again while in the field with it.  I also realize, it's a complicated device, with an intermittent problem, being worked on and taken seriously by hard working folks.

Has anyone else out there had problems with these type of batts (Nickel Metal Hydride) in their SD 302 mixer?

Cheers,

Sean O'Neil

Brooklyn NY

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  • 2 years later...

Just to add in case anyone else is researching this issue:

My 442 was behaving very strangely with AA NiMH batteries today.  Issues included crackling on input 4 and a very weak signal compared to the other 3 inputs.  This was with the battery indicator still a few LEDs into the green.

When I got it home and tested everything out with freshly charged NiMHs the input was fine.  I've still to test with mains adapter and non rechargable batteries.

I'm going to put the 442 in the shop for a service anyway (it's old).  If anything relevant is reported back to me regarding this thread I'll add it in.

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