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-   -   Question on video camera mic (https://www.acousticguitarforum.com/forums/showthread.php?t=201641)

knuckle 12-08-2010 06:44 AM

Question on video camera mic
 
Hello, I got a new video camera, a Kodak i-touch zi10.

It has an external mic capability. I think it's 1/8 female? I can't tell, the jack says mic/headphone, so I assume that this is a stereo 1/8" jack?

So I'm looking for a microphone to use with this video camera. There are some cheapos out there but I don't know anything about this. I have a few xlr condenser mics and I'm assuming that you need an impedance matching transformer like this?

http://www.adorama.com/HOMIT156.html...utm_term=Other

Would this work or am I being an idiot assuming a Rode condenser mic will work with this device? The mic has 9V batter for phantom btw.

Here's a pic of the transformer I'm talking about

http://www.adorama.com/images/large/HOMIT156.JPG

Fran Guidry 12-08-2010 10:27 AM

Yes, the audio jack is a 1/8" (3.5mm) stereo input.

That's a cool adapter you found. When I tried hooking my Shure SM57 up to my Zi8, the chain of adapters was bizarre - unbalancing transformer and impedance converter, one to two channel adapter, 1/4" to 1/8" - and the result was ugly. I think the plug-in power from the Zi8 found the bad connections and generated noise at every opportunity.

I think this cable will do a good job for you, within the limits of the audio circuitry on the Zi10.

I did some comparisons of mics for the Zi8: http://www.homebrewedmusic.com/2010/...the-kodak-zi8/ The info should apply to the Zi10 as well.

Let us know how things work out, please.

Fran

knuckle 12-08-2010 12:14 PM

Also wanted to mention that you guys were complaining about the *.mov files. Well the Zi10 I have is *.mp4 by default.

Ty Ford 12-09-2010 07:05 AM

You don't usually need the impedance matching. That's a throwback from the original 600 Ohm Bell telephone circuits required matching impedance. It's very normal to feed a low impedance source into a high impedance input.

The piece you show doesn't really say what the impedances of input and output are, so there's no real way of knowing if they are really right.

What's the harm with what you have? Depending on the input circuit and mic, nothing to anomalies in frequency response, to unnecessary gain differences.

What this piece does do, assuming that the plug has been wired correctly by feeding pin 2 of the XLR to both tip and ring of the plug. This presents the mono source to both the left and right inputs of the stereo circuit.

There are cables that do this without impedance conversion.

-Ty Ford

knuckle 12-09-2010 07:14 AM

Well I wish I knew that before I ordered it but thanks.

What I always wondered was this. A lot of acoustic amps come with only 1 xlr input for vocals and 1 for guitar.

What would be the harm in using a similar xlr > 1/4" mono adapter in that case?

Ty Ford 12-09-2010 07:32 AM

Knuck,

I'm assuming when you say mic, you mean instrument. It sort of depends on how they implemented the circuit behind the 1/4" . Might work. Might not. If the plug is two conductor (tip sleeve) it might work. A three conductor tip ring sleeve may be more problematic.

The 1/4" input probably has very different electrical characteristics because it expects a guitar or keyboard. Plugging a mic in won't hurt anything, except maybe your ears,

knuckle 12-09-2010 07:45 AM

Yes, my mistake. 1 xlr input and 1 for guitar. I mic my guitars as they are resonators without pickups. I do have acoustics as well, 1 with a built in piezo, the others I close mic or use a K+K meridian.

knuckle 12-09-2010 09:04 AM

Turns out this thing is designed for a dynamic microphone. I don't know how it will work out.

Fran Guidry 12-09-2010 10:25 AM

It will work, because the battery powered Rode looks just like a dynamic mic to the adapter.

Fran

Fran Guidry 12-09-2010 10:27 AM

Quote:

Originally Posted by Ty Ford (Post 2436723)
You don't usually need the impedance matching. That's a throwback from the original 600 Ohm Bell telephone circuits required matching impedance. It's very normal to feed a low impedance source into a high impedance input.

The piece you show doesn't really say what the impedances of input and output are, so there's no real way of knowing if they are really right.

What's the harm with what you have? Depending on the input circuit and mic, nothing to anomalies in frequency response, to unnecessary gain differences.

What this piece does do, assuming that the plug has been wired correctly by feeding pin 2 of the XLR to both tip and ring of the plug. This presents the mono source to both the left and right inputs of the stereo circuit.

There are cables that do this without impedance conversion.

-Ty Ford

The transformer also provides some gain in the process of unbalancing and converting impedance. Handy for using a dynamic into a low gain mic preamp, perhaps not needed with the battery powered Rode condenser.

Fran

knuckle 12-10-2010 03:31 PM

Redid another video. See further in posts

knuckle 12-11-2010 07:05 AM

removed new video further in thread

denmar355 12-11-2010 10:40 AM

zi10 w/ rode mic
 
maybe a bit more gain? video pretty good. too far away though. nice first video IMO.

Ty Ford 12-12-2010 06:54 AM

Some transformers DO provide extra gain, but not all transformers do. Just because they change impedance from low to hi (and the details of what low to what high are unknown) doesn't necessarily result in "free gain."

Then there's the actual quality of the transformer. Not all transformers are created equal. Some may enable impedance conversion but do so at the expense of reduced bandwidth (loss of lows and/or highs) or "ringing" (unexpected and unwanted resonances at one or more frequencies).

I'm not saying that all transformers are bad, not by a long shot, but you do have to do some experimentation to make sure the tool you're using isn't actually making things worse.

There are at least three different topologies in input circuits. Some work well with transformers, some don't, some don't care.

Bottom line, every transformer, resistor, capacitor, IC and coil you put in between the source and the recorder or speaker does something to change the sound. Don't put stuff in the line if you don't need to.

Regards,

Ty Ford

Fran Guidry 12-12-2010 11:37 AM

Quote:

Originally Posted by Ty Ford (Post 2439951)
Some transformers DO provide extra gain, but not all transformers do. Just because they change impedance from low to hi (and the details of what low to what high are unknown) doesn't necessarily result in "free gain."...

Please explain or provide examples of transformers that convert from low impedance to high without voltage gain.

http://www.sayedsaad.com/fundmental/...INDINGS%20.htm includes the following:

Quote:

IMPEDANCE-MATCHING TRANSFORMERS

For maximum or optimum transfer of power between two circuits, it is necessary for the impedance of one circuit to be matched to that of the other circuit. One common impedance-matching device is the transformer.

To obtain proper matching, you must use a transformer having the correct turns ratio. The number of turns on the primary and secondary windings and the impedance of the transformer have the following mathematical relationship

http://www.sayedsaad.com/fundmental/...s/image010.gif

Because of this ability to match impedances, the impedance-matching transformer is widely used in electronic equipment.
http://www.sayedsaad.com/fundmental/...TIOS%20%20.htm covers turns ratio in detail.

Fran


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