MA-100 XLR audio adapter questions

[Don Palomaki]

The difference between MIC and MIC ATT is that the MIC ATT setting reduces the amplitude of the input signal by 20 dB. This may be necessary necessary to avoid overloading the preamps and clipping if you are recording a very loud source, or using a very 'hot" mic. If using AGC mode, it may help reduce the pumping of the noise floor during quiet program material periods.

In most cases you need to be monitoring the audio to help you decide if the MIC ATT setting is the better way to go.

[Jack Smith]

Of course Don is right.I should have reread my post before sending.

[Simon Duncan]

A few more lame questions:

What is AGC mode?
What does AGC stand for?

Thanks

[Don Palomaki]

AGC = automatic gain control. The camcorder adjusts the gain of the audio preamplifiers to try maintain an average recorded sound level. With soft sounds, the gain is increased. With loud sounds it is decreased.

You have this with the REC LEVEL switch set to "A" for auto. The "M" position = manual level adjustment.

[Simon Duncan]

OK a big thank you to all for your comments.

I now have the microphone working via the MA-100 adapter.

But I do notice that when I'm doing some testing with the Mircophone on the camera audio meter I getting a ready of around 12db as peak. On the audio meter this 12db is bolded so I assume that this indicts an audio level average one would like to aim for. I have been doing all this test with the microphone only say some 10 cm from my mouth so this is pretty close.

I have tried switching the audio level over to manual and turning the Level knob right around to Max which does see my audio on the meter peak up around 6 to 2. But when I take the mic say some 30 to 40 cm from my mouth is naturally drops back around the 12db level.

So my question is:
Does this all sound correct?
Ideally what is the level one should be aiming at for interview style recording?
EG is the 12db what I should looking at for a peaking level?

Remember I will be using this for an ENG Interview style reporting so in all honesty the interviewer will most likely have the mic some 30 to 40 cm away from the talents mouth.

As much as I don't want to and can't afford a mixer is there where I'm heading if I want to get good clear audio for my current setup?

[Cole McDonald]

you should try to run with the audio knob around 50%...max will add all kinds of hiss that is full spectrum, so can't be removed well in post. Something called electronics ceiling or basement or something like that causes this.

[Don Palomaki]

The mark at -12 is 12 dB below maximum digital record level (or the point where clipping starts). This is a reasonable level for most (but not all) purposes, and gives sufficient head room so that that sudden loud sounds will not clip. Many professionals use more like 18 dB of headroom in their recordings.

The levels you report with manual gain are characteristic of the relatively low output level of dynamic mics. The final criteria of course is how the captured sound is when you go to edit. You can always adjust level in post, but it is more difficult to remove distortion caused by clipping or overloading the preamps during recording.

The baseline noise is typically set by the first set of preamps, and subsequent amps do not contribute much to it, so it is usually desirable to have as high a starting audio signal as is practicable. But things are not always that simple.

Condenser mics have higher output due in part to having an internal amplifier. Some have higher noise levels from their internal amps than others, and in fact some low cost mics may contribute more noise than the camcorder's preamps, so it becomes a matter selecting and matching the equipment to the best advantage, and operating the equipment in ways that minimize objectionable noise in the final output.

It is worth noting that many people find totally noise free audio some what unsettling, probably because it is unnatural.

[Waldemar Winkler]

Originally Posted by Simon Duncan

A few more lame questions:

What is AGC mode?
What does AGC stand for?

Thanks

Automatic Gain Control.

Very basically, AGC works by the camera's audio gain increasing to maximum until an audio signal is "heard". Then the gain drops down to a level that puts that "heard" sound in proper balance. From that point forward, AGC adjusts incoming audio to keep it within that proper balance.

A pause, or extended lapse in sound, forces AGC to again increase to maximum while waiting for the next audio signal, which repeats the auto adjustment process.

Depending upon the situation, this is acceptable or not. The positive is an average stable signal with annoying high points. The negative is continually variable gain levels which is, at the very least, an invitation to long and tedious audio editing sessions. If you need to use AGC, try to make it the ambient audio track in post.

For live performance shoots at least one of my cameras is set to AGC. The others are fixed to stable audio audio feeds.

[James Emory]

Originally Posted by Don Palomaki

... Many professionals use more like 18 dB of headroom in their recordings. ...

All of the audio guys that have hooked up to my camera with mixers always set their tone level at -20 dB.

[Simon Duncan]

A follow up question regarding the MA-100 used with the Beyerdynamic mic.

I have recorded an interview and when I recorded this I had the Rec Level at 50% since I didn't want to introduce too much interference or noise.

Now that I am editing this the audio is clean but the level are low. EG Sitting between -30 and -40 db.

I can bring up the levels so it sits around the to -20 to -8 which is just acceptable but that is the maximum level my NLE will allow me.

I have 2 questions.
1) Is there anything I can do in post to increase these levels further? (I think possibly not since I have increased the levels to as high as I can)

2) What should / can I do next time I have to do an interview to get a louder and clear sound? EG Is it just a matter of increasing the recording levels? I hesitated with this on this recording due to the fear of introducing too much noise.

[Don Palomaki]

You can export the audio from the NLE, edit it in an audio editing program such as Audition, and then bring it back into your NLE.

Alternatively recapture the audio as analog played back by your MiniDV player, and adjust the audio level as part of the analog capture process.

In general, it is best to record the audio as close to the final intended level as you reasonably can. Amplifying the audio later also amplifies what ever noise was in the original recording as well, so recording at a low level has little or no noise benefit, and may actually hurt overall noise performance depending on the details of the systems involved.

[Simon Duncan]

Thanks Don,

Just a side question.

If I had a camera that delivered 48v phantom power or even a mixer would this give a better recording level of my Beyerdynamic microphone without having to ride the recording level myself?

The reason being with my current setup (Canon XL1 & MA-100) it just seems as though the mic has to almost be sitting on an interviewee's chin to really get a nice solid clean sound. I guess I have abit of a phobia about increasing the recording level too much since I can hear / feel this adding unwanted interference. I see interviewers on TV etc with what appears to be the same mic with it some 20 cm away from the talents mouth and getting good results.

[Cole McDonald]

Dynamic mics have very small regions of good pickup. If you want farther reach, you'll need a condenser mic to get longer throw. Dynamic mics should be about 6 inches or less from the speaker to get a *really* good signal.

[Simon Duncan]

Thanks Cole,

Do you have any preferred condensor mic?

Also how is a condensor mic powered?

Meaning does it require phantom power from the camera or a mixer or do they run from AAA batteries?

Thanks

[Cole McDonald]

I've got a Sony ECM 672 that runs off of a battery (single AA). On our last shoot, we used a Sennheiser 418? (Wonderful-ran off a phantom power inline box that came with it.)

I previously used an Audio Technica ATR55 (also ran off a AA), but since I use flourescents on my set, the audio buzz was unbearable and forced me to use noise reduction in post that ate away at the bottom end of all the voices :( The audio in my short "Scare Tactics" is the result - I also have raw footage from "French Onion" at http://www.yafiunderground.com/bolts.php with the buzzing for your reference. This buzzing was solved by switching to an XLR-based audio system.

There are plenty of good condenser mics out there, I'm personally a big fan of a nice shotgun mic (as you may be able to tell), but I do narrative work almost exclusively so far. I do have a couple of wireless lavs for when I've done weddings in the past, but I haven't used them as much as my shotguns. These mics were used in the car interior in "The Stream, The Cave ,Jim and Dave". They are Audio Technica lavs (not low end, not high end...don't know the model off the top of my head - they're not XLR though).

These forums have tons of recommendations, ty ford has a video on his website that has a good example of several different microphone types. I don't have the URL of that off the top of my head, a search here for him should get you there eventually ;)