Audio trim - same as attenuator?

[Vito DeFilippo]

Hi all,

I posted a sample of distorted audio to the audio section, and the feedback I got was that the camera's preamp was being overloaded and I should get an inline attenuator for my mic (Rode NTG2) for loud venues.

Before I do this, does anyone know if the trim settings in the audio menu actually attenuate the signal before reaching the preamp? Or is it after, and thus useless in my case.

Brooks Harrington, the kind poster helping me out, says that generally, trim in cameras is after the preamp, and thus won't help me, but he has no specific info about the Z1. I would love to know if the trim in the camera would help me, thus avoiding plugging a chunk of metal onto my mic cable!

Anyone know this? I can't find any solid info in the manual or online.

[Vito DeFilippo]

No one has any idea?

[Shaun Roemich]

Not sure if this helps, but on my JVC cameras (and previously on my Sony PD150), I'm unable to use my Sennheiser ME66 shotgun as an ambient mic in loud live music venues, regardless of attenuation, at the camera or inline. I ended up using my medium diaphragm condenser for "room sound". The NTG-2 has characteristics SIMILAR to that of the ME66 in my experience.

[Battle Vaughan]

Vito, you can tell pretty easily by looking at the waveform on your timeline. If it is clipped ---filled with wave from top to bottom --- you're overloaded. If turning down the trim on the camera gives the same waveform, just at a lower level but still filled top to bottom, your trimmers are post-preamp. Some cameras (Canon xha1) have a mike attenuation switch before the preamps, which is very useful. It will usually be labeled as such, I assume. (on the canon it's MIC ATT and knocks off 25 db from the mic signal before it reaches the preamps). We issue the Audio-Technica in-line variable attenuator with our audio kits because some places we work have very hot audio feeds from line-level mult boxes, and they work a treat, not very expensive. A short xlr cable (18 inches) makes them easier to integrate into your line as they then don't stick out of the camera...hth/ Battle Vaughan/miamiherald.com video team

PS it is possible to overload the mike itself, if you are in some kind of rock 'n' roll hellhole, but most have a generous upper limit around 120-130 db...overloading the preamps is more common, in my experience...

[Vito DeFilippo]

Hmmm...it seems I'm getting a split response between overloading the mic and overloading the preamps. I'll have to figure out how to find which one it is.

Originally Posted by Battle Vaughan

Vito, you can tell pretty easily by looking at the waveform on your timeline. If it is clipped ---filled with wave from top to bottom --- you're overloaded.

That's the thing. It's not clipped. The waveform doesn't fill the track. The levels are correct. It's only be listening that I hear the distortion. And it's not the same crackly sound you get when the audio is clipped. It's more like it's just distorting in the bass.

If turning down the trim on the camera gives the same waveform, just at a lower level but still filled top to bottom, your trimmers are post-preamp.

That's actually a great suggestion. I'll try to do a test with my stereo or something to see if I can do that.

PS it is possible to overload the mike itself, if you are in some kind of rock 'n' roll hellhole, but most have a generous upper limit around 120-130 db...overloading the preamps is more common, in my experience...

Boy, it felt like a rock and roll hellhole....

Thanks for all your suggestions, guys. This place is the best!

[Vito DeFilippo]

I did Battle's test, but I'm close to cross posting here, so I'll direct to my post in the audio forum:

http://www.dvinfo.net/conf/all-thing...ml#post1163978