January 18, 2017 at 6:49PM

0

Super long aux cables and plug in power

I just had a quick question about them. I have a rode video micro (that's "micro", not "mic") that I need to run a long (20-25 ft) cable to. The micro uses plugin power, and I know that a good aux cable shouldn't degrade sound quality, but would you see any problems with the power being supplied to the microphone through such a long cable? I can't imagine there would be, but If figured I'd ask anyway.

12 Comments

Bad idea. The longest recommended cable extension for an unbalanced mic is 10 feet. The reason for this is cable impedance, signal degradation and RF noise.

Rode actually make a 3.5mm mic extension cable that is 10 feet long. It costs $11 at B&H Photo : https://goo.gl/7LKgoj

So what are your options ???

1- Connect your mic to a recorder that can be placed closer to the mic. If you have a boom-op, the boom-op could have the recorder in their pocket with a pair of headphones connected to it to monitor what they are recording. You will have to sync with the main camera's audio in post.

2- Rent, borrow, buy a XLR MIC and enough XLR cable, to connect to a recorder or your camera. XLR cables are balanced and can go for 100 feet or more. ( people usually add on a signal-repeater for XLR cables longer than 100 feet, so you can extend your XLR cable as long as you want as long as you keep putting a signal-repeater every 100 feet or so )

January 19, 2017 at 12:45AM

2
Reply
Guy McLoughlin
Video Producer
31211

Thanks for the help. Just a quick question, how do you know the video-micro is unbalanced? I couldn't find anything indicating that in the specs. Are shotgun mics with 3.5mm jacks just unbalanced as a rule? I figured it wouldn't have that problem because TRS cables are supposedly balanced.

Adam Hocutt

January 19, 2017 at 3:42PM

If you use quality cable with an active mic (like yours) 25' is fine. As for the power, that should be fine as well. DC for powering the mic is generally much less of an issue than the audio signal. XLR mics and cables are ideal of course and I highly recommend using a professional mic with with a audio recorder that has XLR inputs. Using an adapter to plug an XLR mic into your camera isn't ideal. Either the cold conductor gets grounded, which is almost as bad as an unbalanced cable or the adapter uses a cheap transformer, which degrades the audio.

January 19, 2017 at 7:09AM

5
Reply

Well now I'm confused XD. I will say that I recognize that XLR is better, and I would use it except that the video-micro needs plug in power, and a phantom power to plugin power converter is out of my price range. It's out of my price range because I'd be recording this video for free, and I wasn't otherwise going to buy a XLR mic, cable, or plugin converter at this time.

I might be able to borrow an XLR mic/cable, in which case that's what I'll plan on using.

January 19, 2017 at 1:17PM

0
Reply
avatar
Adam Hocutt
total, utter noob
154

>>>Just a quick question, how do you know the video-micro is unbalanced?

A standard audio connector does not support "balanced" audio connections, where an XLR or TRS connector does. "Balanced" connectors support a minimum of 3 wires, where one wire is the ground, the second wire is your audio signal in "phase" and the third wire is your audio signal out of "phase".

Here's a quick video that covers the main feature about how balanced cables work and why they can be used for 100 foot lengths or more : https://www.youtube.com/watch?v=BQtMFsw_3Hg

January 19, 2017 at 10:32PM, Edited January 19, 10:33PM

3
Reply
Guy McLoughlin
Video Producer
31211

Right, but most auxiliary cables out there have TRS connectors. For instance, the one linked below.

So, are you safe if you use a TRS cable? Does the cable flip the signal polarity, or do you need your device (microphone) to be able to flip it before sending it down the cable? I don't really need to know this for my original question, I'm just more curious than anything.

https://www.amazon.com/FosPower-3-5mm-Stereo-Audio-Cable/dp/B00LBJ780O/r...

Adam Hocutt

January 20, 2017 at 9:34AM

There's enough independent shooters out there with equipment sitting in closets, I'm sure you'll be able to borrow what you need (including a real audio recorder). I've said elsewhere that I haven't owned a professional video camera (and never owned a DSLR) for over six years now. Whenever I need to do a freelance video shoot, I just rent/borrow. In my case, it's more cost-effective than having to buy new video equipment every few years. I DO own a lot of audio equipment because that's what most of my freelance work is. Likewise, you may do a lot of video work but don't do audio enough to warrant owning good audio gear.

January 20, 2017 at 8:16AM

0
Reply

Right, and that may be what I end up doing. I actually have a tascam dr60d, so I'm good on that front. :D Thanks!

Adam Hocutt

January 20, 2017 at 9:37AM

>>>Right, but most auxiliary cables out there have TRS connectors. For instance, the one linked below.

That's a stereo connector not a balanced TRS connector. The plugs look the same but they are wired differently. The TRS connector transmits two copies of the SAME MONO signal,with one copy that is 180 degrees out of phase with the other copy. ( the audio signal sine-waves are mirror images of each other )

To make this work you need a balanced mic connected to a balanced cable that is connected to a balanced audio input. ( or a balanced to unbalanced input transformer )

January 20, 2017 at 4:34PM, Edited January 20, 4:35PM

6
Reply
Guy McLoughlin
Video Producer
31211

Ah, okay. I was doing some more research, and that's what I found too. That leaves one last question, how do you know the video micro (again, not the videomic or mic-pro) sends an unbalanced signal? I've tried to figure it out myself, but research has lead to nothing.

Adam Hocutt

January 20, 2017 at 6:23PM

>>>That leaves one last question, how do you know the video micro sends an unbalanced signal?

The simple and most obvious clue is that it does not use a balanced cable to connect to your recorder, pre-amp, or camera. A balanced cable has either a XLR ( normal size or mini size ) or a TRS connector, and you can tell that it is using 3 wires to transmit the mic's MONO signal.

Another webpage to check out : http://ehomerecordingstudio.com/audio-cables-types/

January 20, 2017 at 8:04PM, Edited January 20, 8:04PM

1
Reply
Guy McLoughlin
Video Producer
31211

Okay, thanks for your help!

Adam Hocutt

January 20, 2017 at 11:18PM

Your Comment