Sound recording prob

[Ian C]

This place is the fount of all knowledge so I thought I'd ask here first. I've got some sound recording going on, but I've got some strange behaviour with the recordings. See attached screenie for an example.

 

Every wav I record ends up with a higher amplitude below the line than it does above. I've no idea why it's doing it, the zero offset is correct, but it's buggering up my work as the wavs are clipping when they really should be well within tolerances if you look at the top half of the wav. What the hell is causing this?

 

The chain is - Cheapo maplins condenser mike with fuzzy and pop shield, via XLR (I think thats the acronym) cable to a DBX 286A microphone processor, then from that to the line in on my SB Live soundcard in the PC.

 

It's probably not the PC or soundcard as I don't get this problem anywhere else and I've been using the SB Live for aeons.

 

The mike may be doing it, I have reference WAVs from other recordings via that mike but I can't check them at the moment (I'm at work).

 

The DBX is the newest bit of kit but it's pukka rack gear and got unilaterally good reviews, I would have thought an artefact like this would have got it panned? I'm running compression and limiting on it, plus some LF and HF expansion, if that makes a difference.

 

I'm hoping this is a simple "ah yes seen this a million times, do this" problem

 

-Ian

[Ian C]

Looking at my own wavs it only seems to happen once the amplitude gets over about 50% of max - could this be compressor related? I bloody hope not, I bought the DBX specifically for this function

[Branners]

I'm far from a sound expert, but I have seen problems with an amped signal being re-amped by a second set of equipment.

 

If the sound source is adjustable then turn it was down and use the secondary amp system to bring the volume up.

[Branners]

Looking at my own wavs it only seems to happen once the amplitude gets over about 50% of max - could this be compressor related? I bloody hope not, I bought the DBX specifically for this function

 

Thats pretty much the level I have seen problems at.

 

We have a Soundcraft mixing desk at work, running dual XLR in to a major amp system. If we plug in a source and put the source above 50% then we get distortion at higher levels. If we bring the level down to around 25% and then turn the main system amps up then we can go as high as we want with no distortion.

[Ian C]

Well the DBX processor preamps the mike, and that's turned up pretty high (I think somewhere near +10db, it's deffo in the top 80% of the knob) due to the funky way the compressor works. Sounds like that might be my problem there then.

 

I can try turning the gain down on the mike and up the output of the DBX so the output volume is the same, see if that clears up the wierd behaviour.

 

Trouble is, the compressor and limiter work a bit funny, you have to pump up the input to get quiet stuff brought up and the louder stuff limited. I was trying to get this magic bullet where if you whisper, shout, or talk normally it's all pretty much in the same volume range - I kinda had that I thought, but this is cocking it all up. Boo. I might actually have to adjust levels depending on if it's quiet, normal, argument, or proper shouty.

 

Some knob-twiddling for me I think then Thanks JB.

 

-Ian