Topic: Noise from laptop

[balou2]

O.K., so I recorded via laptop for the first time last weekend and got some unknown noise.  The actaul setup was this:

2 x Neumann (on stage) + 2 Nak 300/CP-2 (on stage) + FOH SBD vocal feeds > Berringer mixer > UA-tmod+ > Laptop (USB out) + D-100 (digi-coax).

Since I was mixing on the fly I didn't hear the noise until a between-sets playback.  I started the second set "as-is" so I could determine where the sound was coming from.  After trying everything, nothing eliminated the noise UNTIL I unplugged the USB cable from the UA-5.  During the second show I tried running JUST the UA-5 > laptop and still got the noise, so I know the noise came from the connection.

Here's the question:  Since I ran a DAT copy AND a laptop copy, is there a way to get rid of the noise from the DAT source?  I figure there must be software out there that would allow me to identify what frequency the existing noise comes from and then filter it out. 

Any advice here would be great...especially considering the show came out AMAZING, except for this background noise.

Mike

[dklein]

If it's a simple ground hum, most editors have a 60 Hz + harmonics filter.  If it's something nasty, you can try noise reduction where you build a profile from a silent part (where you can isolate the bad noise) and then subtract it from the mix.  I had something nasty on a soundboard recently that cleaned up pretty nice.

btw - was your laptop by any chance running on house power (not battery)?

[dklein]

here's a before and after - it's just crazy what you can do with software!

[balou2]

here's a before and after - it's just crazy what you can do with software!

For whatever reason, I could not get that mp3.  Regardless....

Thanks for the info.  You mention a "smiple" frequency.  What program do you use to eliminate the sound?

...and yes...I used house power instead of battery.  Enlighten me...this is getting good
Mike

+t

[Scooter]

it could very well be 60 or 120Hz hum.  i have to use a ground lift adapter on my laptop power supply to stop the hum on my rig(when using a/c).  it usually only happens when i'm running a AUD/SBD matrix.  you could try a peak filter at 60 or 120Hz in your editing prog to attenuate it some.

[balou2]

If it's a simple ground hum, most editors have a 60 Hz + harmonics filter.  If it's something nasty, you can try noise reduction where you build a profile from a silent part (where you can isolate the bad noise) and then subtract it from the mix.  I had something nasty on a soundboard recently that cleaned up pretty nice.

btw - was your laptop by any chance running on house power (not battery)?

This is what I'm looking to do.  Do you know if Sound Forge has this harmonics filter?  I'm not really sure what to look for when identifying this sound.  How do you determine what frequency the sound is at?

[dklein]

I don't use Sound Forge but I'm sure it does. 

As far as the AC power, all I can say is I've run into this a coupla times when soundboard patching.  I didn't know it until after and couldn't run any tests but I've been told that aside from grounding issues, house power is often very 'dirty' from all the lighting gear and the board/amp get their own clean power in a good venue.  One time the house tech thought my gear was inducing a hum into the p.a. by connecting it to the board's matrix out (which went away when I unplugged the laptop power). Suffice to say I only run on batteries now.