Sennheiser G3 with Rode VideoMic = HISS

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ericsf

Member
Hey good people,

So I'm trying to use the Sennheiserew112-p G3 wireless system with a Rode VideoMic (instead of a lav) and a Panasonic HMC150 and it's a hiss-fest. I've managed a workaround but wanna know what causes the hiss.

I'm shooting a series of theater performances where the camera is in the back of the room but I'm putting the Rode at the foot of the stage and connecting it to the G3 system and transmitting it back to the camera.

The hiss def comes from the connection btwn the Rode and the G3 transmitter. When I switch out the Rode and connect the lav that comes with the system to the transmitter, there's no hiss. When I use a mini-jack to XLR adapter to plug the Rode straight into the HMC150, there's also no hiss.

A workaround that works is using a little mini-jack extension cable from radioshack I had lying around as a connector btwn the Rode and G3. The extension happens to have a volume dial, but at any volume of the dial, when plugging the Rode into it and then it into the G3, the hiss awesomely disappears. Again, I doesn't have to do with the volume dial because even when I have the dial to max and pump up the volume on the HMC, there's absolutely no hiss. I think it works because for some reason, it doesn't have the same issue when connecting to the G3 transmitter that the Rose has.

Does anyone know what causes the issue in the connection btwn the Rode and the G3 transmitter? Has anyone had any similar issues when connecting other mics into the G3 that aren't the lavs that come with the system?

So glad I was able to find a workaround :happy:, and wanted to share it with everyone but would def benefit from knowing why this is happening cuz I'd like to use the G3 with other mics. Thanks!
 
Just because the jacks physically fit together, you should NEVER assume they are wired to work together. You can't just look at (for example) an 1/8" TRS jack and assume that it's acarrying / expecting a stereo audio signal. It may be balanced audio, it could be an input and an output, it might be video with audio, etc. What about the level? Mic? Consumer Line, Pro Line? Plugging things together all willy-nilly could end up damaging your equipment. Read the manuals, learn what your gear is putting out and what it's expecting as an input.
 
Doesn't the Rode VM have an internal battery power supply. The Senn puts out a nominal voltage (5 volts I think) to power whatever lav is plugged in. This would be a good place to start. There might be a problem solver type product for this from a audio shop. I would try to contact Rode.

Grant
 
The Rode VM is wired to put an unbalanced mono signal into a typical consumer stereo mini jack mic input. It's wired to put signal hot on both the tip and ring of the plug, with the two jumpered together in parallel in the connector so the result is the signal being fed to both the left and right channels in the camera. Signal ground goes to TRS sleeve as one would expect. The G3 mic input, OTOH, although it's TRS, only uses ONE of either the tip or ring on the plug at a time for its signal hot, which one depending on the level of the incoming signal - tip is hot in the cable for a mic level signal, ring is wired hot iin the cable for inputting a line level signal. The unused connector is grounded to sleeve in the cable's plug. By plugging the VM's TRS plug into the Senn's jack, you are shorting the G3 transmitter's mic level input to its line level input inside the connector. No wonder you've got hiss. Also, as ggrantly points out, there's that 5volt bias on the tip to power a lav mic capsule, being fed up the cable into the VM - you need to block that with a capacitor because it could be negatively affecting the mic's own performance.
 
Sennheiser makes a cable specifically designed to hook a mic to a G3 bodypack, it's the CM1. It's not cheap, but that's probably because it contains the capacitor that Steve House mentions. The less-expensive CL2 is also an HLR to "ew" locking 3.5mm, but it's designed for line-level sources that don't care about the voltage the body pack is putting out, and it should not be used with mics.
 
Captain Pierce,

I didn’t know that cables like the CL2 you mention were even made. (In my limited experience, I’ve always seen the Sennheiser lav used with the G3 transmitter.)

I’ve got a decades old Shure dynamic mic (unbalanced, high impedance that doesn’t use phantom power) and wonder if it would work with the CL2 to feed the G3 transmitter.
 
NYvideo,

Products like this are generically called "problem solvers" and the audio shops or BH have pages and pages of them to solve some pretty weird issues.

Grant
 
I'm going to be attempting something similar. I have a Sennheiser G3 (SK100 bodypack transmitter) and want to use it to record the band section in a theatre (left of stage). (I'll also be getting a line feed from the mixer of the onstage audio at the back of the house, I'll be recording at the back). I have both the Sennheiser mike, omnidirectional, that comes in the G3 kit and A Rode Videomic. I'm guessing the Rode Videomic would be better than using the Sennheiser kit mike, is this likely correct? If so what is the best way of connecting them, should I use a 3.5mm to XLR adapter on the Videomic and then the CM1 to the G3 as per Captain Pierce's post? Or should I try a Radioshack headphone cable with volume control? An added question is if I bought the CM1 could I use a Rode NTG-2 (not sure, but I may be able to borrow this for a couple of days) to record the band, is this likely to sound much better that the Videomic? Any other suggestions are also apprecited. Thanks
 
DO NOT use the headphone cable with volume control. The Videomic's output plug is wired so that the tip and ring are shorted together. It's intended to feed a stereo mic-level input, sending the same signal to both left and right channels. But the Sennehiiser G3 bodyback mic input is not stereo, it's mono. When sending it a mic level signal, tip is hot, sleeve is ground, and ring shorts to sleeve. When sending it a line level signal, ring is hot, sleeve is ground, and tip is shorted to sleeve. What you would be doing by plugging the Video mic into it is shorting the mic level and line level inputs together. All the volume control cable does is add a resistor into the short and also reduce the signal level.

Build yourself a short adapter cable with an inline TRS female jack on one end and a TRS male plug on the other and wire it like this ...

TRS-F tip --> TRS-M tip
TRS-F sleeve --> TRS-M sleeve
TRS-F ring unconnected
TRS-M ring connect to TRS-M sleeeve

Plan B: Use the stock Rode 1/8 to XLR adapter (Rode part # VXLR) and plug the Videomic into an SKP100 plug-on tranmitter.
 
Thank you. I don't have the SKP100 plug on transmitter, so I'll make up the cable per your instructions. I think the Sennheiser transmitter puts 5V across the input for the Sennheiser lav, will this cable also get rid of the 5V, or will the 5V not be a problem for the Videomic?
 
wjauch said:
Thank you. I don't have the SKP100 plug on transmitter, so I'll make up the cable per your instructions. I think the Sennheiser transmitter puts 5V across the input for the Sennheiser lav, will this cable also get rid of the 5V, or will the 5V not be a problem for the Videomic?
Click to expand...
Since the Videomic is designed to feed a consumer camera's mic input and they usually have plugin power enabled, I doubt the transmitter's 5 volt bias supply will present a problem. You could always put a 10mfd or so capacitor in the signal line to be sure but I suspect the Videomic already has one built-in.
 
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I butchered a radioshack headphone extension cable and rewired it as per instructions above. Did a quick test, works well with the Videomic. Thanks again.
 
THis is an example of what should probably work it's way high on my audio do's and don'ts. Just because you can plug two things together doesn't mean you should. It's very easy to assume you should if you can and it's not a foolish mistake, more of a manufactures "flaw" that so many use the same connector in different ways. But still it ought to be one of those intro items to learn. Some of these connections can damage gear so it isn't nec trivial to just plug things in and "see if it works".
 
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