Condenser Mic distortion - why?

[cursic]

I'm relatively new, so bear with me...
I thought that as long as the input signal was kept below 0dB on my DAW's meters, the input signal would NOT sound distorted (unless of course the source sound was distroted). But using either one of my two condenser mics (an AKG C300B or a stereo pair Rode NT4) to record a marimba (rubber mallets striking wooden keys, mic placed 18 inches away, pointed directly at the surface of the keys) yields distortion beyond belief. Doesn't happen when using my dynamic SM57, though. The only way to eliminate it is to drop the input level so that the loudest signals barely makes it up to -12dB.

So am I wrong in assuming that there's more to avoiding distortion when using mics than just keeping the input levels below the red line (and these meters are supposedly fast LED meters that should be able to detect fast transients). I know that condensers can't handel high sound levels, but a marimba is hardly a stack of marshall's with volume set set at "eleven!"

Thanks for your input.

[chessrock]

Originally posted by cursic
So am I wrong in assuming that there's more to avoiding distortion when using mics than just keeping the input levels below the red line (?)

Yea. You also have to make sure they're not distorting the inputs of your mic pre. Try turning the input gain down on your mic pre, and the output volume up.

[cursic]

Well, I'm not using a mic pre. Or rather, it's a "built in" preamp that's part of the recorder. I'm using a Korg D1600 hard disc recorder. It supples 48v phantom power. There's an input signal trim knob, which is what I adjust the input signal with, and I keep the peak transients no hotter than -4dB. But I still get a nasty "edge" on most tones. If I lower the input trim to around -dB, the edge disappears, but then the whole signal volume is way down and my noise floor is going to be ridiculously high when I normalize.

[chessrock]

Originally posted by cursic
Well, I'm not using a mic pre.

That could be part of the problem.

[StevenLindsey]

Originally posted by chessrock
That could be part of the problem.

No doubt. The Korg preamps pretty much stink. Get a decent outboard pre. I couldn't get a good sound from the amps in my D8. Started using my mixer pres and a Blue Tube and the sound came alive.

[Tonio]

CURSIC,
Marimba!!!!!!!! yeah!!!
I don't know about the Korg unit you have, what bit resolution
are you recording at? Of course at 16bit, you want it as hot as possible. At 24 bit -4db at peak should be good.

Does the AKg or Rode have a attenuator? Try that.

What kinda genre are you playing?

Good luck
T

[cursic]

Thanks Tonio and all the rest for your responses.
The Korg will record at either 16 or 24 bit resolution. The distortion is still the same at either. The mics do have attenuators, although using them just lowers the overall signal amplitude but keeps the distort. And I'm keeping peak signal levels well below -4dB at the loudest. Funny thing is, the probems goes away when I use an old workhorse dynamic mic like an SM57. Of course, that's a less sensitive mic by nature.....

I'm just confused by the apparent lack of correlation between audible distortion and signal input level (as determined by the LED monitor levels) when using these condenser mics.

As far as genre - ambient/experimental/ethnic/percussion, if that means anything. You ever hear Steve Reich's "Music for 18 Musicians?" That's the kind of stuff I'm into.

[chessrock]

Originally posted by cursic
Funny thing is, the probems goes away when I use an old workhorse dynamic mic like an SM57. Of course, that's a less sensitive mic by nature.....

Lower output, higher spl handling.

[Tonio]

hmmmmmmmmmmmm

did you try to record another instrument, vocal... does it distort?


T

[cursic]

Tonio:
Yeah, everything distorts. Vocals, clap-sticks, acoustic guitar, didgeridoo. I can't believe that at the low volumes I'm playing I'm maxing out the mics SPL-handling capabilities. But what else could it be?

[Tonio]

Cursic,
Did you get the D1600 used or?
I checked the spec on the D1600, its input(1-4 I assume its for mics cuz it says xlr connectors) is only 600 ohms...
which is very low, so it doesn't sound good

Have you tried changing cables? change channels?

It could be a phantom power problem, but I could'nt tell you for sure. Just shooting in the dark but it could be a mechanical problem

You might want to check the user group.

T

[Tonio]

are you sure you are setting up proper input levels?
T

[Tomcat]

Hi Caesar, good to see you here!

Still got that "cricket" problem, huh. I think it's tied up with running the D1600 trims so high. I cured my problem with an M-Audio DMP3 preamp and an RNC compressor. I'm using a Shure KSM27 condenser mic (as well as 2 SM57's and an AT-822 stereo mic). There are better, more expensive pre's, but at my price range ($200) the DMP is about as good as you are likely to get and the RNC (at $175 delivered from Lion Dog in Seattle) will tame those peaks without being obvious or intrusive.

Basically, I think you are simply going to have to get a preamp and compressor to cure your problem.

Take care, and see you over at korgboards.com,
Tom

PS I now run my trims at minimum (fully counterclockwise).