Overloading a microphone?

M

mcmd

New member
I have noticed that when I record one of my amps that I hear distortion on some of the notes (transients). A review of the waveform shows that there is no clipping and still plenty of headroom. So it seems that I am overloading the microphone.

I have tried two small condensers (Shure KSM 109 and a Peavey PVM 480) and got the same result. The amp is a Mesa Boogie DC-3 and I think that the problem is the dynamics of this amp, as it seems to produce a large variation in volume output depending on attack of the strings. I don’t have the problem using an SM47. So, how can I use my small condensers with this amp, besides moving them back off of the amp grill?

Thanks,
Dara
 
You could also be clipping the preamp. The lights don't always reflect every peak, and condensors are sensitive to transients (in general), relative to dynamics. It would be pretty difficult to distort most mics, without peeling the paint from the walls.
 
The pre amp is an DMP3....the waveform ( viewed on the recording app software) is nowhere near 0dB on the transients, so the audio card converters are clean. If I turn down the preamp gain any more, then my signal to noise is going to suck real bad...I'll take another look at my setup tonight...maybe I missed something BIG....
....so I could overload the preamp and not overload the audio card converters....?

Thanks,
Dara
 
mcmd said:
....so I could overload the preamp and not overload the audio card converters....?

Thanks,
Dara
Click to expand...


happens all the time. any place where you boost the signal there is a chance of distortion ruining your signal.
What are the meters reading on the DMP3?
 
I would really check into that preamp. Unless the mic is damaged in any way, I find it really unlikely that a mic of those categories would distort so easily.

Well unless you're pushing upwards of 150db on the amp, to which I say "ouch" (not likely). Also, try using your pad switches on your mics and see if you get any improvement.


My best guess is that the problem is centered around the preamp to computer connection.


Also remember, the output of your preamp is one thing, but depending on what you connect that into, that will continue to determine your signal levels and how hot you can actually go before clipping. So it is possible to hear clipping without seeing it on the waveform. Just another reason why you shouldn't base your desicions too much on what you see, but rather what you hear.

That's what we call "gain staging".
 
I'm interested in your comment that you can't see the clipping on the waveform. Regardless of whether you clip a mic, a preamp, or a converter, something approximating a squarewave is the usual result.
 
mshilarious said:
I'm interested in your comment that you can't see the clipping on the waveform. Regardless of whether you clip a mic, a preamp, or a converter, something approximating a squarewave is the usual result.
Click to expand...

but usually bt the time the waves are so square as to be obvious you've got way more than minor clipping going on.
 
mshilarious said:
I'm interested in your comment that you can't see the clipping on the waveform. Regardless of whether you clip a mic, a preamp, or a converter, something approximating a squarewave is the usual result.
Click to expand...

Ahh good eye. Yeah I think I worded that to sound borederline incorrect.

I guess it's kind of tricky to explain, when I think about the brickwall limiters out there that basically push things to almost the level of a square wave, yet not really clipping. Then on the other side of the spectrum, songs that appear normal visually, but clip. But I suppose that might be more about the monitoring solution.

I suppose the point I was making was for proper gain staging.


Good that you asked that question. Caught me on a brainfart:)
 
giraffe said:
but usually bt the time the waves are so square as to be obvious you've got way more than minor clipping going on.
Click to expand...

Well that depends on how closely you are zoomed in. There are lots of other kinds of distortions than squarewaves, sure, but clipping is a squarewave, even if it's only for 4 or 6 samples.
 
Seeing that you said that this happens only? when you record, so I'm probably wrong about this....but!

I had the same problem recording a Les Paul into a Moogie Mark IIC+, a lil distortion occasionally on the clean channel (when I played heavier) and I realized that my pickups were too close to the strings. I just backed them down a little.
 
Have you considered it might be the amp? Can you try a different speaker cab? I've encountered a few amps which for some reason just do not record well, even though they sound fine in a live setting. Someday I'm going to figure out why.
 
...so I took a look at my set-up last night, and here’s what I see…

The ‘meat’ of the waveform is only about 30% of the full range amplitude and there are short peaks that hit to 70% of amplitude. I took a look at waveforms recorded with the Shure 109, the DMP3 and a different amp (Gibson GA5) and the ‘meat’ of that waveform is 60% of amplitude with peaks to 80% and no distortion. I think the Mesa Boogie amp has a lot of sensitivity and the DMP3 preamp is getting slammed with some of those transients, so it’s not the mics getting overloaded. The recording is clean guitar with plucked cords (no pick). I most often use the Boogie with some overdrive, which would smooth those peaks. I am going to try and mic the Boogie differently....

Thanks for all the input.

Dara
 
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