The laptop connects through USB to the mixer and then from the mixer to the amp rack.
The company I work for has four identical DJ racks. While testing them before our busy season we noticed a loud hum through at least two of our racks and possibly the other two that haven't been tested yet. It always goes away when we unplug the laptop power supply. The supply is grounded and runs through the same power conditioner as the mixer. The laptop connects through USB to the mixer and then from the mixer to the amp rack. The hum does not come out of the headphones connected to the mixer and only comes through the amps. Any thoughts on how to fix this?
I believe that a 600 ohm isolation transformer (1:1) between the mixer output and the amp input should do the job safely, too. Mark C.
But his connection from laptop to mixer is USB. Sent from my iPad using Tapatalk HD
How? Through what device/cable?
Sorry for not replying earlier. Our mains are all fed from the xlr out on the mixer. Some of our subs are fed from an unbalanced RCA output to xlr and others are fed through a crossover. I am thinking that it is an issue with cabling because some of the cables are unbalanced, but it also hums in the amps that use balanced xlr.
Chop the earth pin off your laptop power lead. Lots of power supplies link AC earth to DC negative, hence the laptop chassis. This basically creates an antenna surrounding hard disks, high frequency processors. So yeah chop the earth off. Not really a problem on a double insulated supply.Sent from my iPhone using Tapatalk
Nope. Bad to do, irresponsible to suggest.OP has not seen fit to reply with requested information in the last 10 weeks. Perhaps just ignoring the problem made it go away...
I think it's more to do with the specific power supply or laptop and not just the 'presence of a 3-prong adapter'.
Question though, I've seen many PC's without a ground prong on their adapter. Are these inherently unsafe, or is there something different about those power supplies? In other words, why is it unsafe to remove the ground prong from a 3-prong supply when some PC's only come with a 2-prong supply in the first place?
OP has not seen fit to reply with requested information in the last 10 weeks. Perhaps just ignoring the problem made it go away...
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