TriX Loc: Raleigh, NC

So drums have a very fast attack (fast rise time) and a large dynamic range, so hiss could easily be an issue. I would never use a single-ended mic input on the camera or any other device - the reason is that mic inputs are high sensitivity and high impedance so very susceptible to hum. The answer is to use a balanced line from the mic to the preamp and then use the high output of the preamp to the recording device line input. If you do that, you shouldn’t need a resistive pad to lower the signal level for a mic input.

terskelton

TriX. Yes you're absolutely right in all of that. We are simultaneously digitally multi-tracking. I was hoping to avoid that laborious testing, especially as with what we had it meant recording... then playing back, then recording... then playing back, etc. There isn't a way to do it real time without the ML, which we didn't know about. And IF A: someone else had already gone through this, why reinvent the wheel? and B:, if the camera just couldn't do it, again why spend that time. To me one of the big benefits of the internet is to share knowledge. AND, there was this puzzle of why a classic textbook line to mic level pad didn't seem to work properly in this application? I wanted to learn about that and hoped to run across someone who designed circuits for PCs and cameras who could shed light on that. I would like to know what test SW you use? Thanks... and thanks again for your time.

TriX Loc: Raleigh, NC

I use an ap out of Germany called Audio Tester which you can find at audiotester.de

Good luck with your project!

terskelton

And thanks again for your help. If I discover anything amazing I'll repost.

terskelton

TriX. Our questions and answers may have gotten out of sync somehow so I'm just reading your response starting with "So drums have...". I agree with most of what you say but most mic inputs aren't that high in impedance...maybe 2-3K. But their high gain and if they are unbalanced creates most of their hum susceptibility. The issue in my case is that the camera doesn't have a line level input so we have to deal with the mic input that's there and get the line level output of the mixer down to that. While this isn't an ideal way to record (line level to mic level) I do it all the time without much issue when there's no choice. This particular camera just isn't obeying the rules. Thanks.

TriX Loc: Raleigh, NC

Didn’t realize that there was no line input on the T3i. Reread your original post, and I have no additional suggestions. Sounds as if you’ve already turned down the in-camera mic gain to decrease the in-camera amplifier noise as much as possible and you’ve adjusted the overall system gain to cause the VU meters to hit 0VU on peaks, thus utilizing the max DR of the A/D. Perhaps (sadly) the T3i is just not suitable for this type of work.

terskelton

TriX. Not unless you see a setting in ML to switch from mic to line level inputs.

TriX Loc: Raleigh, NC

Not that the docs mention... BTW, is the same noise there if you use the internal mic?

terskelton

Pretty much... as I recall but it's been six months or more since I did that testing. If you were trying to pick up a person speaking from six feet away it would be noisy. And as I have said and as has been said on-line, folks do use this camera with external sources, but they have to set the manual gain at "1" and then drive the heck out of it. Works, kinda...but not the right way to do it.

TriX Loc: Raleigh, NC

Hmmm. I looked through the T3i manual, and the only possible "gotcha" I saw was one of the mic settings that allowed a combination of the internal mic and an external source, but I'm sure you would have noticed that. I can't see the D.C. Phantom power causing this. And I'm guessing the noise using the internal mic had to do with the AGC turning up the gain. Other than ambient noise, I'm guessing the internal camera noise is caused by the clock and other internal digital signals (a square wave such as a clock, is the sum of all the odd order harmonics up to the rise time of the clock pulse). That type of noise is the result of cramming lots of electronics, both analog and digital into a small space with minimal shielding or signal isolation.