Since the dawn of time, man has had to contend with the infamous “whining” sound on nearby pre-amps when using a Zaxcom IFB transmitter at full power, and even tougher scans on receivers when it is on the same BDS system. Well…. maybe not since the dawn of time, but when you’re trying to figure out a solution to a gear problem to no avail, it can certainly seem that way.
I’m primarily a Sound Devices user. But I do enjoy a good old ERX as my camera hop so that I can get scratch audio and timecode from the same system. I also love having the timecode wirelessly slaved to my mixer. All great things and I do enjoy my setup. But I, like others have noticed that the Zaxnet transmitters don’t always play nice with others. Specifically when its not Zaxcom gear.
Many users have reported hearing a displeasing whine coming in on the nearby pre-amps when using one of these babies at full power. The short term solution to this is to dial down the power output of the transmitter. I have mine dialed down to 5, from 7. But I have heard of people even needing to dial it down to 4, to get rid of the noise.
The issue with doing this, as many people know, is that Zaxnet runs on 2.4ghz wireless. This means that even at peak power output, it will have a lot more trouble transmitting through barriers than UHF will. So you will be very noticeably reducing your range and performance.
And this isn’t even the only issue. After constantly looking for a fix, I also discovered that my RF scans on my talent receivers were a little less clean when the Zaxnet transmitter was active on the same BDS. I realized that my wireless performance was better without the IFB transmitter plugged in.
Some people use 2.4ghz amplifiers on their setups to increase the base performance. But for those who have these issues, this will only intensify the problem. More than a few users have noticed this and have been powering their amps off of separate power supplies than their BDS.
So what does this all mean?
Well, given the fact that the whine goes away for some people when they powered their amps separately, tells me that this is an electrical issue. So I powered my Zaxnet transmitter separately and there was massive improvement. There is some sort of issue with he DC input of the transmitter which causes at least some of this issue. And furthermore, there is some sort of feedback into the BDS from the transmitter which seems to affect the performance of the UHF receivers.
So one could just power the transmitter and amp separately. Yay! But wait. Wasn’t the whole purpose of using a BDS, so that you wouldn’t have to power all of these things separately and you would only have to worry about one battery in your bag? So I kept troubleshooting about what might solve this feedback and input issue without needing to use separate batteries.
I thought about the issue in terms of how ground loops can affect video quality in networked security camera setups. So a lot of them use composite ground loop eliminators to repair that sort of “hum” in the video feed. It occurred to me that this could be a similar issue happening in the DC feed.
So I did some research and discovered two good little boxes which can fix this. Essentially, they are DC to DC converters. They isolate the ground by doing a simple conversion to the same type of current.
The first one above was only 14 dollars on amazon. You’d have to get a barrel converter to fit the 2.5mm DC jack on the Zaxcom products, as the plugs on this are 2.1mm. that shouldn’t be a big issue. The next one from Audioroot is about 100 dollars and uses Hirose jacks, which some may prefer because of the more robust connections.
I have been using the 2.1mm DC version for a month now and the results have been staggering. Using this between my BDS and my Zaxnet transmitter has reduced the whine down significantly, allowing me to increase my output power. But even more importantly to me, it has improved my UHF receiver performance very visibly.
Here is the link to the Amazon page for the first box. *UPDATE* multiple users have reported that the less expensive box has varying success at eliminating the whine and RF issues. The box that we tested was effective, which means that there likely are some quality control issues in their construction. It is, however, only 14 dollars so it could be worth giving a shot. Otherwise the Audioroot unit below will do the job for sure, although it is a tad more costly. Thanks to Eric Carbonara and Gabe Chu for their helpful feedback!
Here is the link to the product page for the Audioroot box. You would probably have to contact your local dealer to find one as it is not on amazon.
I strongly recommend to anyone using Zaxcom IFB systems, to pick up one of these boxes. You may not even know how much it can help. You may be doing just fine in UHF performance and not even realize that your range or reliability is taking a small hit. Test it out. The first one, again, is only 14 dollars or so on amazon, but it has changed the game for me. It could change the game for you too.
Jared Elkin is a professional sound mixer located in Minneapolis, Minnesota.