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Forums Audio Engineering Sennheiser ew 100 noise, but not RF? Stereo related?

  • Sennheiser ew 100 noise, but not RF? Stereo related?

     Ty Ford updated 3 months, 3 weeks ago 2 Members · 8 Posts
  • Mordy Gilden

    November 11, 2020 at 6:44 pm

    I’m having a bizarre issue and having a heck of a time sorting it out.
    If someone can hear me out and help me troubleshoot, I’d really appreciate it! I have a Wireless G2 and G3 system that has been through a lot. Without going into too much detail, both pairs were having hardware issues on either the transmitter or receiver, but I managed to salvage my setup by using the transmitter of the G3 on the G2’s camera receiver, as both of those seem to work, set to the same frequency of course.
    When I plugged in my lav mic, it worked perfectly. Camera got clean and clear audio.

    However, on a quick gig recently, I wanted to boom an interview mic off camera and make it wireless. My plan was to plug my Azden X2 XLR self powered mic into the ew 100 to avoid having wires to the camera. I use an XLR to 3.5mm adapter which I picked up from B&H years ago for this very use. I know I could just get an SKP100 on the back of the mic like they say I should, but I already own the body pack transmitter and I’ve done this literally hundreds of times with my G2 system without any issues. For some reason, using this G3 transmitter, I’m getting a ton of static noise. It doesn’t sound like RF interference (which in my experience sounds like repeating cyclic noise), but more like a constant hiss. I tried scanning for open frequencies and changing channels, but it didn’t go away.

    Here’s where it gets interesting: Thinking maybe my mic is bad, I plugged in a different mic (a cheap dynamic hand-held style I keep in my gear back as a backup), and the hissing noise was completely gone. Using the same XLR to 3.5mm adapter.
    But plugging the original Azden mic and that same XLR adapter into the camera directly, clean sound. Curious. The mic and cable don’t seem to have a problem. Then I plugged it back into the Sennheiser transmitter, and discovered that there was hissing noise even BEFORE I ATTACHED THE MIC. Whether the Azden was connected or not. Just the cable itself was creating this hissing noise. But when I plugged in the dynamic handheld mic, it went away. When I plugged in the Azden, I get sound + hiss. Bizarre.

    Even curiouser: I plugged in the lav mics, and sure enough no hiss. Works fine. Figuring there’s something funny going on with that xlr adapter (even though it worked fine with the dynamic mic and worked fine directly into the camera), I tried plugging my Rode VMP into the G3 Em 100 body back transmitter. I mean, they are both 1/8″ 3.5mm jacks, so it should just work fine I figured. I GOT HISSING. SON OF A #$%^.

    So I know it isn’t RF interference, there’s something causing this noise in the jack, it seems. The only thing I can think of is perhaps something to do with the pins on the TRS jack? The rode VMP jack is a stereo TRS (delivers dual mono), and the XLR to 3.5mm adapter I think also is. The lav mics are mono (only tip and sleeve). I happen to have a 3.5mm breakout cable that separates the left and right channels (good for feeding two sources to a Zoom H1), and I plugged my Rode VMP into one side and got hissing. But plugging into the other, I got clean sound!

    So there’s something fishy going on with the G3 bodypack’s 3.5mm jack. Does it not handle TRS connections? And if so, why did the G2 do this perfectly fine? Additionally, why do some mics like my dynamic handheld one work even using the XLR to TRS adapter without noise, whereas other mics I tried have noise?

    I feel like I’m missing an easy fix or something here. Thoughts or ideas?

  • Ty Ford

    November 11, 2020 at 8:30 pm

    Hi Mordy and thanks for contacting the Cow Audio Forum.

    Nice description of your situation. Plenty of details.
    Sounds like that adapter cable may not be the one you want for that job. I know you said it used to work in the past, but XLR to 3.5 mm can be wired differently.
    If the cable is for a balanced audio connection, the tip, ring and sleeve are wired one way. If the cable is for unbalanced audio, the cable can be wired another way. If the cable is for a stereo unbalanced connection, the cable can be wired a third way.

    I forget if there are any wiring difference between the G2 and G3, but that may have been the problem.

    Regards,

    Ty Ford

    Cow Audio Forum Leader

  • Mordy Gilden

    November 11, 2020 at 10:20 pm

    Thanks Ty! Yeah, I was thinking something along those lines. I did have the issue once with an adapter that I *thought* was recording in dual mono, but turned out it was recording inverse channel on the other side (results of a balanced connection). After editing together and putting up on google drive for the client to review, we found that anyone watching on a phone found the audio muted in those scenes. I blamed their phones because it CLEARLY worked fine on my computer, until I tried it on my phone and noticed in low bitrates it did the same thing. Apparently, Google was combining everything into one mono channel in the low bitrate preview compression, and the inverse audio channels were cancelling each other out!
    That was a real head scratcher, took me a while to figure that one out!

    So I was thinking this might be something similar, however why does the dynamic mic on the same adapter not have the hissing issue? And as far as I know, the Rode VMP with it’s DSLR-friendly 3.5mm jack isn’t a balanced connection either, so why does that not work yet mono connection lavs do? I’d say maybe the G3 doesn’t like TRS plugs, but again… it worked with the dynamic mic. Does that make sense? Do some mics balance and others not? I thought it was a cable thing?

  • Ty Ford

    November 12, 2020 at 12:11 am

    I had the exact same polarity thing happen with a stereo/mono to cell phone thing. I never made that mistake again. Hahahaha.

    Dunno. Not all mics are balanced the same way. Some are “electronically balanced” some are transformer balanced. Might be something in the polarity circuit. l I had a LD condenser with a LOT of noise a number of years back. Dynamics, OK. Other condensers OK.

    Regards,

    Ty Ford

    Cow Audio Forum Leader

  • Mordy Gilden

    November 12, 2020 at 4:17 am

    Thank you for making me feel like I’m not the only one! LOL

    So bottom line, what should I do? Fork over more money for the XLR “butt plug” adapter? That still won’t allow me to use mics like my Rode VMP. I don’t use it wirelessly often as its really an on-camera mic, but I like knowing that I CAN, since it always worked on my old G2 setup when I tried it. Should I get a TRS to TS cable? Or does that defeat the purpose of balancing audio? Or does the ew-100 not even support balanced audio anyway?

    Not really sure how to proceed here.

  • Ty Ford

    November 12, 2020 at 12:32 pm

    Hmmm, well, I’m gonna guess that your on-camera mic would probably not make a good boom mic. What make and model is it?
    I’m pretty sure that the G2 and G3 mic inputs are not balanced. In one iteration, tip, sleeve was for mics and ring, sleeve was for line. I may have that backwards. I forget. Anyway…unbalanced. The thought being that the cables were short enough to not pick up much radiated noise.
    Playing with cable has become a hobby for me. I have tons of cables with different connectors for just the reasons you’re seeing.
    Regards,

    Ty Ford

    Cow Audio Forum Leader

  • Mordy Gilden

    November 13, 2020 at 2:32 am

    “I’m gonna guess that your on-camera mic would probably not make a good boom mic. What make and model is it?”

    Most mics, sure. I’m using the Rode Video Mic Pro (original model, it’s been updated since). It’s an adorable mini shotgun that does a pretty incredible job at isolating who I’m point it to, even at a bit of distance. Aimed at the subject’s mouth just out of frame, it seems pretty on par with my Rode NTG2 and Azden shotgun setups, and avoids background noise admirably. I saw it used on a short film shot upstate from where I live once and remember thinking, gosh that’s a weird use for an on-camera mic. But then I tried it once and was blown away. It’s pretty versatile. I used it with other wireless setups before to make it work, and it had no business working as well as it did. 🙂

    It appears to have a TRS plug (hardwired) which gives dual mono. I don’t think it is balanced. The cord is too short and designed for DSLRs. I’d think it is unbalanced + unbalanced, but clearly something isn’t what I expect here. Maybe I should just make myself a mono adapter for this.

  • Ty Ford

    November 13, 2020 at 3:13 am

    My favorite is a Schoeps CMC641. Inside or out. The Audio-Technica 4053b is next down.
    Depending on what you’re feeding, the XLR wired to a TRS with tip and ring wired to positive and ground to sleeve is a good bet.

    Regards,

    Ty Ford

    Cow Audio Forum Leader

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