Couldn't I use a Rode VXLR adaptor, run through a XLR cord, and then plug into the HV20 via a Hosa XLR-mini jack adaptor?

Or is a beachtek the only way of getting balanced audio in this situation?

P.S. An audio tech claimed the Videomic is balanced because is has a 200 ohm output impedance. I'm not sure what that means.

200 ohm just means it's low impedence, which is a good thing. It doesn't mean it's balanced.

Over a length of 20 feet balanced vs. unbalanced isn't going to make any noticeable difference. Adding connectors to both end of a balanced cable will introduce more noise than a simple unbalanced cable will.

The output impedance of a microphone is irrelevant to the issue of it being balanced or not, find another audio tech.

The VXLR adaptor simply lets you connect the unbalanced mic to a balanced input, how you're planning to use two adaptors will not achieve anything. Just use a shielded minipin extension cable of the length you need. You may get away with it because the Rode has a built in preamp and has a fairly high output level.

My biggest concern is that you're running a mechanically unreliable, fragile cable and connector system a long distance. You're using up cast and crew time that could be wasted by cutting corners. Get a camera or a field recorder that's built for the job at hand.

Bob.

> Couldn't I use a Rode VXLR adaptor, run through a XLR cord, and then plug into the HV20 via a Hosa XLR-mini jack adaptor?

You could but it would be a total waste of money. Just use a 20' stereo cable and you will get the same result.

The XLR cable itself does not reduce the interference (although it is better shielded that a stereo cable). The way the interference reduction works has to do with the three wires and some electronics. The signal is carried on two wires and is phase inverted on one wire. Any RF noise that gets picked up by the cable, gets eliminated when the phase is inverted back at the other end thus putting the noise out of phase and canceling it out. This is done in the electronics of the mic and the preamp that you plug it into. So simply using an XLR cable with an unbalanced mic will not help because the electronics are not there to do the phase inversion.

The XLR adapters you are referring to are just conforming a three pins connection into two pin connection. They are not actively balancing the line.

> Or is a beachtek the only way of getting balanced audio in this situation?

No, the Beachtek is meant to be used with a balanced mic (XLR). So it takes a balanced mic with an XLR connection and allows you to plug it into a camera with an unbalanced stereo jack. It has electronics to maintain the balanced line so you get all the benefits of using the XLR cable. Unfortunately, you are starting out with an unbalanced mic so the Beachtek can't do anything for you.

> P.S. An audio tech claimed the Videomic is balanced because is has a 200 ohm output impedance. I'm not sure what that means.

Output impedance itself is not directly related to being balanced or unbalanced although all balanced XLR mics that I've ever seen are low impedance. The Videomic may be balanced but the Rode website does not say (at least I could not find it). What 200 ohm impedance tells you is that it is a low impedance mic as apposed to a high impedance mic. This makes it compatible with an XLR input on a camera that is expecting a low impedance mic. This is why the simple passive XLR adapter works.

If you can't get the mic further from the camera, then bring the audio recording closer to the mic! In other words, have the Videomic on a short boom pole with a solid state audio recorder at the other end. You can use a MicroTrack or other inexpensive audio recorder. You can even use an old Sony MiniDisc recorder. Anything solid state will do.

~jr

Thanks for the response.

What if I used this thing http://www.bhphotovideo.com/c/product/423360-REG/Hosa_MIT156_MIT_156_Low_to_High.html#goto_itemInfo to connect to the camera?

If it's a transformer, will it actually change the impedance from high to low?

Hi everyone, sorry I missed the responses before I posted my last message.

So the general (low-budget) consensus is that I should get a regular 20' stereo mini extension cord?

Just need clarification; I really appreciate all the responses.

> If it's a transformer, will it actually change the impedance from high to low?

No it will actually convert from Low to High (read the description):

Hosa MIT-156 Low to High Impedance Matching Transformer with XLR Female to Stereo 1/8" Miniplug Male Connector

You would use it with a mic that has an XLR to plug it into a camera that has a mini-jack. This is exactly what the Rode Videomic does for you already. That is the beauty of the Rode Videomic. It eliminates the need for all of these. They solved all of these problems for you. It's just that you are trying to use it for something it was not intended. Like I said it's a great "on-camera" mic.

~jr

> So the general (low-budget) consensus is that I should get a regular 20' stereo mini extension cord?
> Just need clarification; I really appreciate all the responses.

Yes. That is the cheapest first step. If that causes too much hum and interference then look at picking up a small solid state recorder and use that closer to the source with a shorter cable on the Videomic.

Make sure you test the 20' cord under the same conditions as you will be shooting in. If there are florescent lights, then test it under the same florescent lighting. If it's by a police station with a police radio, test it next to a police station. Preferably test in the same location as the shoot. You want to know well in advance if that 20' cable is going to turn into an AM radio antenna on the day of the shoot! ;-) Good luck.

Oh and absolutely, positively, keep your headphones on at all times and monitor your audio signal. You don't want to be surprised.

~jr

Great answer JR. Just wanted to add that this is one case where using a good quality cable will make a noticable difference. If you use a really good quality 20' extender cable you should get good results, especially if there is no strong interference nearby. Use a cheap Radioshack headphone extension cable is asking for trouble however.

Don't forget, you could also use a remote recorder for audio and match it up later. It could be an 'audio only' recorder or just another camera set up in a convenient place. (2 angles to choose from too.)

Thanks everyone, great advice!

I'll try a good quality stereo mini extension cable.

There's no fluorescent lights in this room, so I should be okay.

Thanks again everyone!!

The signal is carried on two wires and is phase inverted on one wire. Any RF noise that gets picked up by the cable, gets eliminated when the phase is inverted back at the other end thus putting the noise out of phase and canceling it out.

Just to add to this, for those that don't understand "balanced" vs. "unbalanced," here's a short primer:

These two techniques approach the problem of keeping out unwanted electrical interference using diametrically opposite approaches.

In the "unbalanced" approach, a metallic shield is placed around the wires that carry the signal in an attempt to keep out the interference from electromagnetic waves floating around the room from dimmers, fluorescent lights, and many other things. So, in this approach, the operative phrase is "keep out."

In the "balanced" approach, the shield is optional and often not used. However, the two wires carrying the signal are wrapped tightly together so that interference will affect them identically. In this approach, it really doesn't matter if interference enters the signal wires, as long as it affects them both equally. So, in this approach, the operative phrase is "let in, but affect identically."

The longer the wire between the microphone and the final destination for the signal, the bigger the "receiving antenna" for the unwanted interference. As the wiring gets longer in length, it becomes impossible -- no matter how good the shielding -- to completely keep out unwanted interference. Thus, you HAVE to use a balanced approach if you use long cables. Even if you can keep cables shorter, balanced will almost always have less unwanted interference.

So why doesn't every mic setup use balanced?

Cost.

The cable wiring must be wound very precisely to ensure that both wires get hit by the interference in the same manner. Also, because the wire is twisted together, it takes more wire to make a foot of balanced twisted cable. The most important contributor, however, to the cost is the signal amplifier which must amplify the difference between the signals in the two wires, while rejecting the common interference signal that has been induced in both of them. When dealing with the micro-volt level created by a microphone, it takes some pretty fancy circuitry to retrieve that signal when the "common mode" interference signal is measured in volts (i.e., a million to one difference). Good circuitry costs money, even in this day of miniaturization, especially since the actual construction of the circuit paths must be done quite precisely.

For your application this has gotten way out of proportion. 20 feet? Is that right? You won't have a problem with interference unless you string the cable along the lighting tracks. Does not matter balanced vs unbalanced or headphone extension cable vs Hosa adapter and XLR. All will work and if you hear noise you will likely be imagining it as a result of all the well intentioned responses to your post. I have run 100 feet of XLR to an Audio Technica AT822 stereo microphone and used a similar Hosa Adapter (mic came with one) to go into the camera in an auditorium with no noise. None of it was balanced, but I ran it under the auditorium floor not across the floor or the lighting system. I just got back from shooting a musical rehearsal. I had the AT822 on the stage apron with 25 feet of XLR over to the tripod and the XLR to mini-stereo adapter going from the cable to the camera. No noise. None.

John

Sorry but I have to disagree. All the headphone extension cables I've looked at are not shielded. The conductors are not even shielded from one another. Using them would be a big mistake.

The rest I go along with.

One of the biggest problems today is finding gear that's really balanced. Decades ago I worked with an old school radio guy and he'd have none of this new fangled transformerless stuff. Being a young know it all I thought him nuts. Since learned my lesson. Good mic transformers are very expensive (Jensen or Lundahl) but they're still the only way to really do it right.

Bob.

John,

That is really interesting, since I know you do a ton of stage work. I would have thought that with all those dimmers and everything that your audio would have gotten hosed.

Your post is especially interesting to me since I purchased that exact same mic about a year ago -- based on your recommendation, if I remember correctly. It is a wonderful more or less general purpose mic. It is unbalanced, but uses XLR connectors. The kit I purchased includes converters to phono and mini plug. It also included a stand, all sorts of clips and adapters, wind shield and more. All for $105.95 on eBay (including shipping). Best money I spent all last year.

Thanks!

Perhaps I've just been lucky so far, but I have run mic feeds over 80' of stereo miniplug cables (four 20' cables strung together) many times without any attenuation or noise issues. The trick is to make sure you're using SHIELDED stereo cables, not the headphone extenders that are common. Both types are available at any Radio Shack store.

There is no doubt that XLR connectors are about a thousand times more rugged than stereo miniplugs, but electrically I've never noticed a difference.

My favorite mic is my AT822. It's what I usually use to feed the aforementioned stereo miniplug cables. A few months ago I had the opportunity to set up the AT822 on its own mic stand in close proximity to a very nice (and very expensive) dual-mic setup used by a successful local recording engineer. I was able to get a feed from his DAT recorder and recorded it as well as my AT822 microphone. Boy, the two recordings sounded close, so much so that I wouldn't hesitate to intercut one with the other and I doubt very much anyone could tell. Could be wrong but I was personally surprised by the results.

Whatever cable you buy make certain it a SHIELDED cable!

I'd even buy two and cut one open just to make certain. I once bought a box of extension cables out of a bargain bin. Much to my surprise they were headphone extension leads, just three unshielded wires run in parallel, not even so much as a twist in them.

Perhaps your safest bet is to get someone to solder one up for you.

One other BIG trap. Some of the minipin plugs and some cameras don't work too well together. The moulding on the plug is too fat and fouls the camera body so the plug doesn't actually lock into the camera socket. We had a client loose the audio from a wedding reception due to this. And seh was certain she could hear the audio in the headphones.

Which brings me to my next tip. Buy either sensitive headphones or a head phone amplifier. None of the cameras have enough power in the headphone amps for you to really hear what is going on. We use Takstar DJ headphones, they're over 10dB more sensitive than our uber expensive Sony 7509 cans. The Takstars are useless for mixing but for listening to what a cheap camera is recording they're ideal and cheap.

Bob.

Sorry but I have to disagree. All the headphone extension cables I've looked at are not shielded. The conductors are not even shielded from one another. Using them would be a big mistake.
====================
Good point. The ones I have are shielded. I think I got them from Parts Express. Still, I was thinking more of the short length (20 feet). Non-shielded still might be a mistake though.

John

John,

That is really interesting, since I know you do a ton of stage work. I would have thought that with all those dimmers and everything that your audio would have gotten hosed.

Your post is especially interesting to me since I purchased that exact same mic about a year ago -- based on your recommendation, if I remember correctly. It is a wonderful more or less general purpose mic. It is unbalanced, but uses XLR connectors. The kit I purchased includes converters to phono and mini plug. It also included a stand, all sorts of clips and adapters, wind shield and more. All for $105.95 on eBay (including shipping). Best money I spent all last year.

Thanks!

==============
You're welcome. I am happy I have helped you with something on the forums. Seems like you have helped me more times than I can count and I have always appreciated that.

I never run my cables near anything that could generate electrical interference, especially the lights. There is usually access through a trap door to the area beneath auditoriums. That is where I go to run cables. I usually come up through into the sound panel. From there I go to wherever I have my camera. Usually around 100 feet total. Never a hum or anything in the audio.

As Riredale and others have stated the Audio Technica AT822 is a fantastic microphone. You got a real bargain John. I paid around $250 for mine. Best money I ever spent.

I also constructed a cable to split the left and right outputs from the mike to be able to adjust them independently from a mixer. I plug the left and right XLR into separate channels in the mixer. Works great. I also use the splitter cable with a Beachtek adapter so that I can adjust the left and right level during a rehearsal. If someone walks to stage right and I want to amplify that side I lower one channel and raise the other all from a single stereo mike. Here is a sketch of the cable I built.

[IMG=http://i2.photobucket.com/albums/y40/craftech/AT822toXLR.jpg]


Link.




John

FWIW.
XLR is a more solid connection - as it clips into place, which helps prevent accidental unplugging/slipping/loose connections, although a cheap XLR plug/socket is naff - neutrik definitely know how to make good xlr connectors.

Balanced has additional benefit aside from being able to remove noise - in that when being recombined/flipped, you get the additonal benefit of a 6dB boost in signal due to 2 complimentary signals being in phase.

Headphone cables can seem to be non-shielded, and that's clearly sometimes true, but obviously there's an electrical insulation barrier to stop shortening of signals (which is a git as you can't easily solder these cables when modding/repairing cheap tat experimentally.

XLR can be both balanced, or unbalanced, and the same is true for stereo jacks, whereas mono jacks cannot be balanced

DI boxes can be used to convert jack->XLR and also provide a balanced output

X = Ground
L= Live (hot)
R=Return (cold) - short out with X on unbalanced

dont mean to hijack this thread...
i am looking for a mini in, stereo mic... to use with my canon xh-a1 hdv cam..
can someone recommend one?
this will be used for shorts/docs etc... just an overall good mic! (stereo)

thanks
pj

What is your price range? The Audio Technica AT822 is perfect, but it still goes for around $250. John Meyer said he found one on eBay for $105.95 which is an amazing price. Check eBay.

John