AB batteries/UL2 + Sennheiser Evolution: noise!!

[Jan De Wever]

Hi gang, posting here since not only audio is involved.

This is the setup:

- Canon XL1
- MA100
- Anton Bauer Gold Mount plate (to use their batteries on an XL1)
- Anton Bauer Hytron 50 battery
- Anton Bauer Ultra Light 2
- Sennheiser Evolution 100 beltpack reciever, velcroed to the back of the battery plate
- reciever XLR-out to XLR input on MA100, microphone level

The Anton Bauer batteries feed the XL1 and the UL2 together. It's a great setup, except for one big problem:

When I have the UL2 connected (turned on/off doesn't matter), I hear a faint but very distinct noise on the wireless reciever, even with the wireless microphone turned off! It's sort of a high-pitched sharp sounding noise with a rattling sound in i. Turning up the recording volume on the XL1 increases it, turning up the output volume of the reciever doesn't increase that noise. It comes in at around -40dB on the XL1's audio meters. When I put my fingers on the mini-jack connector that comes out the reciever, I can hear the noise change in volume and 'pitch'. But when I disconnect the UL2, all noise is gone and I get crystal clear sound form the wireless mike.

I would appreciate any tips to get rid of this noise! I see no other place to attach that reciever, so it needs to stay at the back of that battery plate.

Any solutions please?

[Don Palomaki]

Sounds like switching power supply bleed through somehow. Does using a separate power source for each device clear it up?

[Justin Chin]

Interesting. Are your power cables and your sound cables parallel to each other? The shouldn't be. I know when setting up a studio, your power and audio cabling should not run together, but run ACROSS each other. When cables run parallel you're likely to get some bleed through (as Don suggested).

Just a thought.

[Jan De Wever]

When I used an older battery powered light, from a different battery, I didn't have these problems. But I bought this setup specifically for this purpose: one battery to power both the camera and the on-camera light. It does this job perfectly for over 4 hours!

I've tried it all: running the audio wire from the side so it never touches or crosses the power cable, having the cable that feeds the light on the other side of the camera, ... Nothing resolves this but disconnecting the light, which I don't want to do, obviously. At work we have a DSR250, with BPL60 batteries and the same Sennheiser reciever/Ultralight 2. No problems there!

Other ideas?

[Don Palomaki]

Try not using the MA-100 preamp if you can. See if that makes a difference. Also, try keep the MA-100's power and audio output leads as close to each other as you can. See if that makes any difference.

[Jan De Wever]

Thanks for the suggestions, but neither helped solve this. It seems I have a mass-problem. If I connect a copper wire to the outer part of the mini-jack output of the reciever, and with a long (2m) wire connect it to the battery-plate, creating a mass, the noise is gone. If I use a short cable, just enought to bridge that distance, the noise remains ...

It seems like an electrical problem, but I don't know how to solve it ...

[Nathan Gifford]

I'm guessing that the UL2 has some kind of switching power supply that is causing the problem. The reason the DSR250 is that it probably uses balanced audio while the XL-1 does not.

What you might try to do is to tie a choke (like the ones you see on the power cords on CRTs) on the cord from the UL2. That may help. The trick is getting the noise out of the UL2 and out of the XL-1.

[Jan De Wever]

Thanks Nathan,

any idea where I might buy such a thing, and what that might cost?

[Nathan Gifford]

Many PC supply houses and Radio Shack have them. They cost just a couple of bucks. They come in two pieces and you loop the cable through, then lock the two halves together.

If you've got some junk PC gear you might be able to salvage one off the cord.

[Jan De Wever]

Hi guys, I found no way to make the noise go away, other than moving the Sennheiser reciever to the side of the XL1. I tried it with isolators on the power- and soundlines, creating a mass-connection from the Sennheisser mass to the metal battery mounting plate, ... nothing resolved it well. I've now mounted it with several velcro-strips on the tape-door. Not a solution I really like, but it seems I have no other choice.

I might build a little box to carry it in, but in that case I will have to drill holes in the tape door to mount it, or glue that box to the door. In both cases I will be damaging my XL1.

Other suggestions?

I will be reviewing the Anton Bauer battery/UL2 combination for the XL1 shortly on abcdv.com. Thanks for the support!

[Nathan Gifford]

You know one other test might be interesting. Leave the UL2 hooked up to Anton Bauer battery and mount the standard battery on the cam. Also try just using the onboard mic too. Maybe the UL2 is being conducted into the power feed to XL-1.

One thing surprises me about this. Usually when you use design a switching p/s you select a frequency and its harmonics outside the normal hearing range.