Unecessary feedback when laptop is plugged in. Please help.

Hey yall

My MPC lets out nasty feedback when I have my laptop plugged in. The moment I disconnect the laptop plug the feedback is gone. I've got one plugged into one outlet and another plugged in across the room. The wires are not near each other. Any idea what gives?

by laptop plugged in do you mean the MPC is producing feedback when you plug just the laptop's power cable in? is there any audio cables hooked up before giving power to the laptop?


most feedback loops are created when the sound producing device is also receiving that same sound back in. it gets its FEED sent BACK, producing a loop in which the signal feed is recombined and amplified over and over. very common occurence if you have the Main outs of the MPC going into the line in on the laptop and then the laptop out back into the record in on the MPC. if this is the case, go into RECORD mode on the MPC and turn the Main Monitoring to OFF.

if you have weird noise from the MPC1000 just from plugging a laptop in across the room, that's probably not feedback, but a dangerous electrical wiring problem. in this case, take your gear to a friends house to see if it's the gear or your house wiring.

I appreciate your reply....

is there any audio cables hooked up before giving power to the laptop?

Yes. Does it make a difference?
Does one need to power on the laptop first?


I only get the bad feedback when I got the MP hooked up to my computer via the Mbox2 interface.
And I've tried it at three different locations so far, so yeah about that dangerous electrical wiring problem....

Audio cables are primary ones that may cause the problem with feedback IMO.Of course it makes a difference.

loveflake wrote:I appreciate your reply....

is there any audio cables hooked up before giving power to the laptop?

Yes. Does it make a difference?
Does one need to power on the laptop first?


I only get the bad feedback when I got the MP hooked up to my computer via the Mbox2 interface.
And I've tried it at three different locations so far, so yeah about that dangerous electrical wiring problem....

ok, good. from your post it was unclear if you had simply gotten weird noise just by plugging the laptop in across the room. so i'd say your house wiring is fine.

as i said before, feedback is caused when a sound producing device starts receiving and reproducing its own output. somewhere in you connections you have created a signal loop, it might be on the laptop, the mbox or the MPC, or some combo....

the order of power on won't make a difference in terms of preventing the feedback but it might make you figure out which pair of devices is causing the loop.....

i would start with the settings on the mbox. as you said, the feedback does not happen unless you hook everything up through it. you may need to turn monitoring off inside either the mbox or the MPC, then you will no longer hear the sound being produced twice which is what causes feedback....

electric dragon wrote:

loveflake wrote:I appreciate your reply....

is there any audio cables hooked up before giving power to the laptop?

Yes. Does it make a difference?
Does one need to power on the laptop first?


I only get the bad feedback when I got the MP hooked up to my computer via the Mbox2 interface.
And I've tried it at three different locations so far, so yeah about that dangerous electrical wiring problem....

ok, good. from your post it was unclear if you had simply gotten weird noise just by plugging the laptop in across the room. so i'd say your house wiring is fine.

as i said before, feedback is caused when a sound producing device starts receiving and reproducing its own output. somewhere in you connections you have created a signal loop, it might be on the laptop, the mbox or the MPC, or some combo....

the order of power on won't make a difference in terms of preventing the feedback but it might make you figure out which pair of devices is causing the loop.....

i would start with the settings on the mbox. as you said, the feedback does not happen unless you hook everything up through it. you may need to turn monitoring off inside either the mbox or the MPC, then you will no longer hear the sound being produced twice which is what causes feedback....

That just might be it. I'll try it out. Appreciate it fam.

ATTN electric dragon:

It's not the monitoring either.
I've done some testing and here are my findings:

The MPC and my computer's headphone out cannot be plugged into the same soundmaker (ie amp, speakers, stereo). They fight with one another. They make this terrible high-freq pitch.

Regardless of what they go through (mixer/interface/amp), the speakers hiss.

Is there anything I can do about specifically that?

loveflake wrote:ATTN electric dragon:
....The MPC and my computer's headphone out cannot be plugged into the same soundmaker (ie amp, speakers, stereo). They fight with one another. They make this terrible high-freq pitch....

sounds to me like it IS the monitoring, and you identified the loop (between the MPC and the laptop....)

when i say monitoring, i don't mean it's the monitors (speakers, amp, etc) i mean inside the device is a usually a function called monitoring. this is basically a button or switch you engage that let's you hear an input source.

do a quick experiment, set your rig up, make the feedback happen. to fix it you need to figure out which device(s) is receiving AND monitoring inputs from whichever other device is ALSO recieving and monitoring its own inputs, here's how i would check the MPC: as soon as feedback starts turn the REC GAIN wheel all the way DOWN on the MPC. if the feedback stops, you have a loop in the MPC. to fix it you need to figure out which device(s) is receiving AND monitoring inputs from whichever other device is ALSO recieving and monitoring its own inputs.....

if that doesn't help then you are going to need to list exactly how you have things setup when the feedback happens, for example:

MPC1000 - MAIN OUTS >> MBOX2 IN (via 1/4 inch cable pair)

MBOX2 >> computer (via USB, firewire, whatever it is)


just list all the INS and OUTS you have setup, including the laptop, the MPC, the MBOX and the AMP/MONITORS.

dude, just put ur laptop on battery power.. The noise is coming from the laptop being powered.

Peace

yeah did u try unplugging the laptop _power cord_?

if that helps, you can also use a simple 3-prong to 2-prong 'ground defeat' adapter between the laptop plug and the wall.

my dell has that problem.

HOWEVER, I HAVE HEARD THAT DOING THAT IS DANGEROUS. So, I can't really tell you to do that . (but it might work). (just don't do it.)

I HATED THAT PROBLEM.