Laptop Hum
This page is a stub. Please help by adding more information if you can. Thanks ST 20:29, 8 December 2007 (GMT-7)
From the Dell Audio Faq "How do I eliminate the buzzing noise from my speakers or headphones that occurs only when my system is connected to AC power?
Ensure that both the computer and any external speakers are plugged into the same outlet or power strip. This should eliminate or minimize the buzzing associated with a ground loop. You should not assume that all outlets in a single room are on the same circuit. Outlets may be on different circuits, even when they are close to each other. In studio type situations where buzzing associated to a ground loop is unacceptable, an isolation transformer can be used. An isolation transformer should eliminate the problem, but is typically expensive. While a three to two prong wall outlet adapter (removing ground) will eliminate the noise, for safety concerns this solution is definitely not recommended. "
Laptop (notebook computer) power supplies are notoriously noisy. The quick test to find out whether this the culprit, is to simply unplug the power and run off battery. If the noise goes away, you know it's the power supply.
Your best bet is a two-channel passive DI box with a ground lift switch such as this:
http://www.audiopile.net/products/DI_Boxes/FDB-202/FDB-202_cutsheet.asp
Hope that helps Hilmar
See it in context
There are several reports on the Bose® Pro Portable PA Community that the EBTECH Hum Eliminator works for removing hum when using a laptop power supply.
See: search results for Ebtech on the forum