Zoom H6 RF Interference

[William Guth]

Did you actually get good signal? Or just something decent enough to work with?

This happened to me today for the first time in downtown Chicago. I was 26 floors up on Michigan Ave in a sleek modern building of metal and glass, so basically inside of a giant antenna, stones throw from two radio stations and a TV station.

In my situation, the RF interference was actually slightly amusing. In all of my 15 years of AV experience, and countless wireless transmitters/receivers I never anticipated my first RF interference would occur in a wired system. I didn’t think to switch on the -db pad, and I don’t know if that would’ve helped, but I’ll consider it next time it happens.

Your initial post was a while ago, and I’ve learned today that Zoom has acknowledged the issue. No idea if any design updates have been implemented. Too late in both our cases.

I was able to mitigate it a little in post-production. The recorded radio sounds were extremely faint. Much more faint then they were when I was listening to them live through the headphones.

That said, I still plan to conduct continuity tests of all my XLR before I take any of it out in the field again.

[Tom Strand]

This happened to me today.

Zoom H6 – (4) XLR cables + Sennheiser microphones.

I’m using the Zoom to add more microphones to a conference room with a built-in videoconference system. So I use the line out (TRS 3.5mm M/M cable to a Rhodes 3.5 to XLR adapter) then XLR into a room XLR jack in the wall.

The line out is set to -20dB so the Zoom output doesn’t over-drive the room audio system.

We picked up a radio station with varying intensity. Loud enough to be distracting during a videoconference.

Solution 1: Use the microphone out (instead of line out) turned down to Volume 50. So far so good.

Next attempt: Set the line out to -40db or more, hoping to get low enough not to propogate the interference.

[Ty Ford]

Hello Tom and welcome to the Cow Audio Forum.

1. Any time you go unbalanced, you grossly increase your probability of interference.

2. What’s a Rhodes? I know Rode, but not Rhodes. Rode makes an adapter, but it is not clear if the adapter is wired to convert an unbalanced stereo input to a balanced XLR output or not. Your RF problem could be happening right there.
I’ve asked Rode to comment.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Tom Strand]

Ty,

Thank you for the quick response.

re: Rode. It’s a Rode VLXR as described https://www.amazon.com/Rode-VXLR-Adapter-VideoMic-Mini-Jack/dp/B000Y021NA/ref=sr_1_1?s=electronics&ie=UTF8&qid=1525904511&sr=1-1&keywords=rode+xlr+adapter.

I assumed the M<>M 3.5 TRS connection between the Zoom H6 line out and the Rode 3.5 F <> XLR M was balanced. But that may be the only unbalanced link in the chain. Does a balanced 3.5<>3.5 M cable exist? Or maybe a 3.5mm M <> XLR F single cable would work. I thought the VLXR would do the magic to prevent AM radio interference.

WORKAROUND: Yesterday I was able to use the MIC out and reduce the volume to 10 so that online people wouldn’t hear the interference. I’ll try that again tomorrow. I tried the LINE out, but the miximum reduction is -30 dB which wasn’t enough to hide the radio interference.

Tom

[Ty Ford]

I have an email in to Rode. I t seems it’s an unbalanced stereo input (3.5mm) to an XLR male. Questions remains about the stereo/mono balanced/unbalanced thing. Normally, this unbalanced to balanced thing results in problems. Yes, you can hear the audio in balanced audio land, but when you play it back in mono the sound source disappears because you putting positive peaks on one half of the waveform and negative peaks on the lower half of the waveform.

“Does a balanced 3.5<>3.5 M cable exist? ” Sure, but everything depends on the sending and receiving circuitry. It’s a plumbing issue. A 3.5mm TRS has three conductors. If the cable is properly made those three conductors can pass a balanced mono signal. If the cable is plugged into a stereo output, it carries the unbalanced stereo signal. Plug that into a mono input 3.5mm input and you may have problems unless the tip and ring of the cable are tied together, making the signal mono. It’s still not balanced, but it will combine the two track into mono.

Questions?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Ty Ford]

Tom,

I heard back from Rode. The adapter is setup to combine unbalanced stereo to mono. The XLR carries unbalanced Mono.

If you wanted to balance it, use really short unbalanced cables and put it through one of these.

https://bhpho.to/2rvvMJE

After balancing, you’ll have a much better chance of not hearing the AM.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog

[Tom Strand]

Ty,

Thank you for the guidance.

I would guess that what I need is a Hum Eliminator for only the 3.5 mm leads.

As you can tell, my beginner brain thought that a TRS cable (vs TS) took care of interference, but of course, the intelligence isn’t in the mechanical presentation of the cable, but in the circuitry and physical wiring of the cable.

For now, I will keep the microphone output at 10 (or less) or move closer to the XLR jack that links to the room system.

But game for any adapter options pre-wired to help remove the AM radio.

Tom

[Ty Ford]

Hi Tom,

You could get a 3.5mm TRS to two Male 1/4″ Y-cord and plug that in to the box
Keep that cord short.

” the intelligence isn’t in the mechanical presentation of the cable, but in the circuitry and physical wiring of the cable.”

yup, you got it!!! There are transformers in the box to create a balanced circuit. The balanced circuit is he intelligence that will allow the radio station to be cancelled out.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford\’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford\’s Blog