Microphone is clipping...

[joeyk]

Wasn't quite sure, where I would post this, but I figured since I think the problem is with the mic recording this wouldn't be a bad place to post. Anyway, onto the problem!

I recently, went out and bought a pre-amp for my computer, along with a Shure SM57 so I can record some of my drum tracks. (Yes, I realize I should have overheads, and blah blah blah. I just don't have the money to do this all @ once.) Anyway, It seems that the microphone is clipping the input sound. (As in, getting overloaded or something.) I end up with clicks, and pops.

I was just wondering if there were any suggestions on how to fix this problem from the masters of it. I've tried changing mic positions and what not, to see if that helps, but to no avail. I'm beginning to wonder if I made the right investment in the equipment I chose to record with.

[joeyk]

Yeah, here's a clip from it, just to give you an idea of what it's sounding like. spiryx.net/stuff/drums.mp3 It sounds like a cd skipping as a friend of mine put it.

Just copy and paste the url, it wont let me post an url link yet =(

[billisa]

This doesn't sound like clipping to me, and it doesn't seem to be happening at the point when clipping would be most likely. My guess is it's another issue.

[joeyk]

Any thoughts on what could be the issue then?

[Shadow_7]

Yeah, not clipping. Clipping would be when it gets distorted. Or the top level volume shows up as a straight line. Maybe likely when a computer is involved, but highly unlikely when a human being is responsible for activating the sound generating device for each beat/note.

Sounds more like a realtime priority thing. At least that's what it would be in linux. Try closing as many apps/processes as possible including networking. And see if you still have the issue.

In linux you'd add something like this to /etc/security/limits.conf

@audio - rtprio 99
@audio - nice -10
@audio - memlock 65536

And start jackd like this:

$ jackd -R -d alsa -d hw:0 -s -S -r 48000 &

And then start your sound recording application like audacity or ardour(2).

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If you're recording from a USB device, you might check the cable/connection. That could be contributing to the issue.

Your gain is a little high though. Or you compressed and normalized it in post production. Try turning down the gain on the preamp. And the input level up on the soundcard / recording device. As/if needed. You don't really want to exceed that 50% waveform height while recording. Since any sort of accent / loud part will clip. And you probably want it lower than that at sound check since people tend to take it up a notch when performing live.

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My interpretation of that issue is as follows. Computer resources get hogged (cpu and/or ram or even data I/O). Causing the recording app to take a back seat while some other app does something. When it returns to your sound app, it's skipped a few bits of data while waiting on that other app.

It could also be a latency issue. Recording at too high of a samplerate for the bus speed. Not enough ram, so it's swapping to a file (big performance hit). Trying to write to the disk in realtime and writing faster than the device can handle. If you're recording from a USB audio device, while writing said recording to a USB drive. On the same usb bus, that could also account for some latency issues.

[joeyk]

Mm, well yeah.. I traced the problem down to latency, I find that if I run audacity with a nice value of 1, it seems to be working fine, happen to have a better not-so hacked solution though? =)

Mind you, this is a 2.2GHz IBM Thinkpad, with like 384MB of memory. and I think I put 512MB of swap. so, it's not the best system in the world, but it should be doing the job of recording just fine, I'd imagine.

[Shadow_7]

Audacity is a RAM hungry app. In linux I prefer to use Ardour for anything of any length to record. Less resource hungry, more stable, and otherwise saves it to disk in realtime. So if your laptops battery runs out, you still have everything up until your battery died on the harddrive.