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-   -   A-T 835ST - When to use the roll off? (https://www.dvinfo.net/forum/all-things-audio/26818-t-835st-when-use-roll-off.html)

Art Cohen July 17th, 2004 03:33 AM

I'm on the tip of my seat! How did it turn out?

I'm looking at buying sound gear to record a Marching Band and a Drum Corps with a GL2, so I'm very interested in what you come up with.

My best so far has been a mono DR4000 condensor....which was all I had on hand. It certainly beat the on camera and a Sony I bought to try.


George Ellis July 19th, 2004 12:05 PM

I think it was a success. I ran about 25% manual onboard, the attenuators online at -20db, and around 55% on the preamp. While I was recording, I did not hear any of the noise. I have to check it out in post. I am pretty sure it is 'fixed' as I took the camera down and then put it up sans attenuators for the Retreat. During the America the Beautiful/Oh Canada, I could hear the problem again. I was able to do an audio check and calibration during Carolina Crowns performance to get my levels. During their blasts, I did not hear a peep of the crackle. I have to admit that I was busy framing during Spirit's performance, but I did not hear it.

I will post a clip on my webpage for a comparison when I can.

George Ellis July 19th, 2004 09:40 PM


Ok, maybe next time? -20db was too much. The audio is not as bright as it should be. -10 next. Hope I get a chance.

David Ennis July 20th, 2004 09:58 AM

Troubleshooting a problem that only appears intermittently is a nightmare. Ask any repairman. You come up with a theory of the problem that correction "A" should fix. So you want to test the effect of "A" vs. "no A" on the problem. But since the problem comes and goes with no correction applied, the chances of getting a false indication about "A" are pretty good.

Crackling is definitely the clipping of peaks of waves somewhere in the sound reproduction chain. If it's because the 835ST puts out an electrical signal too strong to be handled by another part of the system, then attenuation will help. But if it's because the mic element is being overdriven by sound pressure, electrical attenuation won't help.

Although either or even both could be happening, from my armchair I woud put my money on the sound content overwhelming the mic. When waves mix, two interesting effects occur. The first is that new low frequency ("difference frequency") waves are produced. These would respond to roll off. The second is that wave amplitudes can add to and subtract from each other. From time to time, the chance combination of added waves may exceed the sound pressure input spec of the mic.

Yeah, I'm overly analytical. But the bottom line is that pulling back from the source would tend to correct either cause.

Also *really* watch out for what I said in the first paragraph.

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