Audio limiter?

[Michael Mann]

Did Canon forget to include an audio limiter? I hope it is just hiding from me ...

[David Morgan]

a... I don't think so.

:-(

[Brad Tyrrell]

I think the effect is available. Oddly, we just don't get to control it much.

I get the effect by going auto and playing with combinations of the attenuator and audio gain. I haven't really tested the extremes but it works like soft limiting at the top with a level roughly set by the attenuation/gain combination. Kind of Rube Goldberg but it works for me.

[Michael Mann]

Brad, thanks for your proposal, meanwhile I tested the following combination:

- Sennheiser MKH 418 (a stereo version of the MKH 416), XLR inputs
- A1 phantom ON (both channels)
- A1 attanuator ON (both channels)
- A1 AUTO gain control
- A1 NORMAL audio gain sensitivity

First I was worried that the auto gain mode of the A1 might produce to much "pumping" of the audio. But it sounds more like soft clipping - what I was looking for.
The only drawback might be: Auto gain control usually produces more preamp noise than a (lowered) manual gain control. But I am going to test this.

[Brad Tyrrell]

Originally Posted by Michael Mann

First I was worried that the auto gain mode of the A1 might produce to much "pumping" of the audio. But it sounds more like soft clipping - what I was looking for.
The only drawback might be: Auto gain control usually produces more preamp noise than a (lowered) manual gain control. But I am going to test this.

Yeah, I was quite pleasantly surprised by the auto sound mode. I really don't know how the sound is being "auto-ed" but the effect at the top is like you say - "soft clipping".

Experimenting with my set up, I found that on auto sound the high end seemed to be nicely limited. Unfortunately, the median level was way to high, so I clicked in the attenuators. I then found the median level too low so I added a +12 gain on the menu while leaving auto sound on. That seemed about right. (I figure -20 + 12 = -8 ??)

Like I say, I don't really know what the camera is doing, but the effect is what I wanted. It doesn't seem noisy or "pumping" to me although my audio needs are not super critical (yet). Maybe someone else can explain, but meanwhile, I'm happy.

[Michael Mann]

Originally Posted by Brad Tyrrell

Experimenting with my set up, I found that on auto sound the high end seemed to be nicely limited. Unfortunately, the median level was way to high, so I clicked in the attenuators. I then found the median level too low so I added a +12 gain on the menu while leaving auto sound on. That seemed about right.

Brad, what microphone are you using on your A1?

[Brad Tyrrell]

Originally Posted by Michael Mann

Brad, what microphone are you using on your A1?

Michael,

My circumstances may be somewhat different than yours but...

I shoot events and most often find myself in a gymnasium or auditorium with TERRIBLE acoustics. My low-tech solution to the "cave" sound is a Crown pzm. Works great. I get very decent sound and the pzm effect almost eliminates all those reflections. I find a nice flat surface somewhere close to the action, duct tape the pzm to it, run 100' to 200' of XLR cable to my spot in the balcony or bleachers or tree, and shoot. (Sometimes I mount the pzm on a 2' x 2' black ply-wood and hang it.)

Until the A1, I used an XL-1. The four channels let me conveniently back-up and sometimes enhance the sound by combining in post, but now...? I guess I'll be looking for a camera shotgun to somehow match with the pzm so I can still get the back-up.

It's interesting that the A1 on auto sound is letting me by-pass my usual phantom powered pre-amp and line level compressor/limiter. Really convenient for my environments.

On a side note, - I have to get my old vari-zoom lens controller working again. I kind of love the rings on the A-1, especially the iris. But, with the zoom on full tele-photo, even on a tri-pod, you can detect my pulse.

Brad

[David Morgan]

I'm going out to CES in two weeks. I'll try to find someone who knows at the Canon booth. This is would be good to know

[Michael Mann]

Wow Brad, that sure differs from my simple MS-Stereo shotgun setup!

Originally Posted by Brad Tyrrell

It's interesting that the A1 on auto sound is letting me by-pass my usual phantom powered pre-amp and line level compressor/limiter.

I am sorry, I didn't get that. How do you manage that? Thanks in advance.

[Michael Mann]

Originally Posted by David Morgan

I'm going out to CES in two weeks. I'll try to find someone who knows at the Canon booth.

Yes, please do that!

I already tried to convince Canon Service by phone that an audio limiter is on the wishlist of A1 users, but I am afraid the service member did not know what I was really talking about - sort of mixed it up with the audio attenuator, which the A1 already has. But he promised to forward the "please include audio limiter or soft clipping feature in next firmware update" proposal to Canon Japan.

[Brad Tyrrell]

Originally Posted by Michael Mann

I am sorry, I didn't get that. How do you manage that? Thanks in advance.

On the XL-1 there was no limiting and even on auto sound you could easily drive the audio past 0db, - painful! Sooo... I ran the camera mic on auto with attenuator into Channels 1 & 2 for back-up and ran my pzm through a pre-amp with phantom power and line level out into a "over easy" limiter compressor into Channels 3 & 4 on manual audio line level. Worked fine with Scenalyzer & Premiere.

I tried the XH-A1 auto levels combined with the -20 +12 like I said, and found I could power the mic through 150' of cable and get what sounds like "soft limited" sound directly without the other boxes. Happy Camper!

[Allan Black]

Originally Posted by Brad Tyrrell

Like I say, I don't really know what the camera is doing, but the effect is what I wanted. It doesn't seem noisy or "pumping" to me although my audio needs are not super critical (yet). Maybe someone else can explain, but meanwhile, I'm happy.

Played around with this today at the shop, I found the effect being talked about but couldn't find an explantaion of it anywhere. Has anyone else made any further progress? We record noisy aircraft programs and need good limiting. TIA.