RFI interference causing a problems

I am helping a friend of mine set up a podcast. What I thought was going to be a fairly simple technological project has turned into a crazy complex project.

Here is what he wants to do.

  1. Use Zoom (skype like program) to talk to people and record the conversations so that he is on one track and the guest is on another track. He will use the same computer to record as he will to conference call.

Gear he has.

  1. He has a zoom H5 2 channel interface.
  2. SM57
  3. Macbook
  4. Small Behringer mixer with one aux.

Here is the current setup.

  1. His mic into the mixer. Panned Left
  2. Mac pro headphone jack to the mixer. Panned right
  3. Main outs of the mixer goto the interface inputs L&R. I did not use balanced cables here.
  4. He monitors from the Aux output of the console.
  5. record the audio from the H5 in garage band.

Everything works as expected except that we are getting a lot of RF interference on the recorded tracks. I should have tried balanced cables from the mixer to the interface when it was at my studio. There is not much when we monitor from the console. Unplugging the headphone jack from the mac pro solves noise the problem. I tried setting the system output to the H5 instead of the built-in and using the h5’s headphone and line out jack and I could not get this to work. It always got feedback. I am assuming from crosstalk of the interface because I had channel one and two completely isolated. Are there any other ways you can think of to hook this up? Also, do those RF filters and hum eliminators work?

Hopefully these are good questions. I’m just trying to fully understand.

What is the reason he wants separate tracks? Editing and mixing capabilities? Is he really going to spend that much time preparing tracks? Would some audio sound checks on the front end of the conversation get the best balance possible and bypass all of this?

Also, is he recording the conversation on Zoom (the online conference program, not the interface, for purposes of this question :slightly_smiling_face:)? You can record the video of your session which will include the audio, of course. That can then be edited in a video program, to take out bloops and guffaws. No control over separate audio though, AFAIK.

If he does use the recording feature of Zoom (the online conference program), it is going to have both of their voices on there. If he’s trying to re-route the audio somehow the other person won’t be able to hear him online. So while they are chatting on Zoom, if the sound of the Zoom call is going out the Mac headphone jack that is going to have both of their voices on it. I don’t see any way around this.

I say just record the call on the Zoom platform, and he can edit it in a video software app if he has one. But if he only wants audio (like most podcasts, though some people publish them on video) he may be able to just export that from the video editing app.

Have you tried an actual Zoom call to test this? I think the Zoom audio (again, the online conference program) going out the Mac headphone jack is going to have to have both of their voices on it. That in itself is not going to allow him to separate the audio. His guest is going to have to hear him through the Zoom conference program which means it will be in the Mac headphone out.

Is this making sense?

  • Oh, and if he does record the Zoom call (there is a feature for this on the screen tools) he will need a Dropbox or something to have the video file posted to. They are large files, of course, and I don’t believe Zoom hosts them on their platform. Or if they do it’s probably only on Premium accounts or for an extra fee.

Great questions. At first I thought just record the zoom call and were done but…it records in really low resolution. There is all kins or artifacts and it won’t be acceptable for a podcast:(

He wants separate tracks for editing. Actually, it’s me that wants separate tracks because I’ll be editing the podcasts for a while until I can train him to do it:) After he edits the storyline of the podcast It will only take me about 15 min to get the audio where it needs to be.

We actually have everything working except the RF interference out of the headphone jack. We have just the interviewee"s voice coming out of the mac HP jack.

Thanks for your interest in this stan:)

1 Like

Are you 100% sure it’s RFI and not a grounding issue? What happens if you remove the charger from the laptop?

If it is RFI, then the first thing I would try is balanced cables.


There was no difference when the laptop was plugged in or on battery power. I could reduce the interference when I placed the monitor as far away from the 1/8th inch trs cable coming from the headphone jack. It is a high pitched whine with static at 750hz and 3000hz primarily.

I will definitely try balanced cables.

1 Like

Or shielded cables? :confused:

I know that when I run unbalanced cables to my monitors from my interface, I get ugly RFI whenever I move my mouse. switching to balanced cables got rid of it completely.

1 Like

Sweet. I will definitely get him back out to the studio and try that. Thanks.

Hmm, I haven’t checked into the Zoom audio specs, but like any streaming they may be relatively low. However, I have used Zoom quite a bit and the audio quality has always been quite good. With Skype, at least in the past, audio issues and cutouts and blips were frequent. The only issues I have noticed with Zoom are when someone is obviously connecting on a weak WiFi signal and both their video and audio freeze or cut out.

Are you sure it isn’t the RFI getting involved there too? I know of conferences and meetings being recorded on Zoom that are as good quality as many podcasts. And that does become a question is: “how good does our podcast audio need to be”. Believe me, I have listened to some podcasts with horrible audio and have even bailed on them because of it, but I have seen some of those podcasts have high listener-ship and subscription rates even despite the audio. As with music, the standard that audio engineers see as necessary may be well beyond the ‘requirements’ of the average listener.

I also saw one thing where a guy started a podcast in two weeks from having the idea. His suggestion was to “just get started”, not be a perfectionist, and you can improve your workflow over time and learning. Getting listeners and followers supports that. I think there has to be the interest there in the first place to even continue with the podcast series, which won’t be known until it is tried and the response gauged. I’m assuming this is a new venture for your friend and a first time podcast effort.

I’m certainly not suggesting lowering your standards for good audio, if that’s a crucial thing for the podcast to succeed, like if the audience is musicians and audio nerds. Just that new podcasts are almost always a venture and search for an audience, and can be a work in progress.

Also, while it might not be feasible for some guests to record their own audio, that’s one way to handle it. I believe it is done quite often. I would assume the recordings are started (and ended) as simultaneously as possible, then the guest saves their audio off as high-res MP3 or WAV at the end. Due to file size, it would then have to be a link to a Dropbox or sent by Hightail. Bring each speakers audio into a DAW and sync them up, then edit.