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Hello

I hoping someone maybe able to help here. We have a rehearsal/recording space next to a machine shop and have problem with a certain CNC machine which has end coders. Whenever I plug in my guitar a guitar amp head and the machine shop guy has his machine on I get a terrible RFI problem through the guitar amp, and when he turns the machine off it goes away instantly. The noise is like a constant super high pitch drilling sound and I hate it. It really sucks.

Initially, when we moved in we had an electrician install a new mains wiring on a spur system, with a new mains distribution box etc. We had the RFI problem but didn't know at the time what was causing it, so we called in the electrician to install a new clean earth which didn't cure it either. Eventually we discovered the machine that caused the problem, called in our electrician again and was told we need a mains filter, isolation and regulator unit, this would cure the problem. Luckily we located one of these quite cheap and he installed it, but unfortunately this didn't kill the RFI problem either. The electrician tried alternative wiring on the mains (switching phases (we have 3 phase coming in) hoping the machine on a different phase to our audio spur), lifting the earth off altogether etc, but nothing got rid of it. Our electrician has now gone away saying that the problem is incurable other than to ask the guy to turn off his machine when we are recording guitar.

The space I have is available to me a on a long term basis and the machine shop is not planning on moving, so at the moment we are stuck with this problem. Is there anybody here who may be able to suggest a way of eradicating it?

thanks
Jason

Wow I can't believe the isolation transformer didn't do the trick. That CNC must be kicking out some crazy RFI.

Perhaps the CNC machine is so poorly designed that it's actually broadcasting RFI. In which case the power has nothing to do with your problem. The guitar lead is acting as an antenna and picking up your neighbors big drill show? Just guessing.

Others on this board will have better solutions then this but maybe if your friendly with this guy you could have some kind of mu metal shield built to go around the control unit/broadcasting part of the CNC machine? If it's not too big.

Or you could build a shielded box in which to record guitars?

Both of these are expensive and speculative.

Your problem is probably EMI, not RFI.

Electromagnetic interference can be almost impossible to get rid of.

Just ask Steve.

EA had a similar situation, only it was a photocopier, if I am not mistaken, causing the interference.

It's going to be next to impossible to isolate yourself from this interference w/o total shielding.

If it's important enough to you to practice during the operation of this device, then you're probably looking at a Faraday cage for your practice space....

Yeh, I thought the isolation box would sort it, but no.

I think your right that its broadcasting RFI or EMI, its a really big machine, quite old, its on most of the time, sometimes on all night and thats really frustrating for us. It only comes through the speakers when the guitar is plugged in, like you say the cable/guitar pickups are acting as an antenna.

thanks
Jason

atmosphere wrote:It only comes through the speakers when the guitar is plugged in, like you say the cable/guitar pickups are acting as an antenna.

This is EMI. For sure.

Sorry. It's not easy or cheap to fix. Unless you can shut down that machine somehow.

Out of curiosity, what should be done in such a case? a Faraday cage is what they use to block eavesdropping of cell phones and such, no?

Shielding the Transformers on the amp with nu metal wouldn't help? I guess that not since it's the guitar being the problematic.

eliya wrote:Shielding the Transformers on the amp with nu metal wouldn't help?

Dude, no:



But yes, shielding the guitar's innards with foil may help a bit, but probably not enough by the sounds of it.

I hate that nu metal.

lol. I'm such an idiot. yeah, mu metal I meant.

Is there any way he could use a balanced (or pseudo balanced) connection between guitar & amp to help reduce the interference?