High Pitch Whine -- Please HELP!

[kritzer]

I have a high pitch at 15750Hz, 10780Hz, 8020Hz, 5250Hz, 2775Hz when I record through an Rode NT1 through a Firewire 410 into my laptop. The buzz changes when I hit the record button (it becomes a lower pitch). I do not have a buzz when playing back normal music or using a regular input like a guitar. I do not think it is the microphone but I do not have access to another.

Please let me know if you can help!

Andrew

 

[SRR]

Does it go away when your laptop is on battery power?

 

[kritzer]

It does NOT. It is not related to a 60Hz ground hum or anything. Thanks any more ideas??

Noise does stutter off and on when changing the volume in the mixer panel of the firewire 410 or the software control knob. Doesn't change when using the hard drive though. CPU issue?

Thanks,

Andrew

 

[dgatwood]

Sounds like a badly designed DC-DC board without sufficient choke/filtering, resulting in GPU/CPU clock noise leaking into the ground. Since the FW410 is bus-powered (or wall-wart-powered), your entire ground bus is floating, so that noise can easily end up in your audio. (I'm assuming the laptop has a two-prong power cord.)

Do you have any gear with a three-prong plug? Try plugging that piece of gear into an unused jack on the 410 and see if the problem goes away (or is reduced). If so, you should try zeroing your ground with a custom grounding pigtail cable....

 

[kritzer]

Isolated Issue

I have isolated the issue to it only happening with an XLR cable with 48V Phantom Power on and any input on the other end (guitar amp on or off - XLR out or Rode mic).

Anyone know why the phantom power would cause this high pitch noise? Perhaps I need a better mic cable?

Andrew

 

[fraserhutch]

Does it go away when your gf leaves the room?

 

[ez_willis]

I have a high pitch at 15750Hz, 10780Hz, 8020Hz, 5250Hz, 2775Hz when I record through an Rode NT1 through a Firewire 410 into my laptop.

Please let me know if you can help!

Andrew

Apparently my girlfriend is in the same room as the mic. Tell her to go home.

 

[ez_willis]

Does it go away when your gf leaves the room?

Damn you! Beat me to it!!