Ableton Forum

I have an M-Audio Black Box for guitar and it's quit as a mouse until I turn my computer monitor on ( big burtha old school CRT ) and then it makes everything too noisey to record. It does it with a Pod or any electronic device. You cut the monitor off and everything is quit again. Do LCD Flat panel monitors help this problem. MY TV in the living room does the same thing to all my gear. what's a Ground lift? I tried running an extintion cord to a seperate room run off a different breaker. didn't work.

CRTs give off a shite load (especially if it's a big motha as you say... lol I used a 21" Trinitron CRT before getting my 19" LCD...) of EMI (electro-magnetic interference). This is basically magnetic fields and radio waves. Anything that's not shielded well will pick this up. Electric guitar pickups are basically magnetic sensors.... they pick up magnetic fields, so a CRT is giving off noise energy of the same sort that your pickups are trying to listen to.... the result is that you hear all of the radiation through your pickups.

Badly shielded cables will exhibit this too to a small extent, but the most other most likely cause is a ground loop (since you said it isn't only your guitar). I couldn't be bothered going into the electronics right now, but the basic principle is that if different 'grounds' in your electrical wiring are connected via a loop, that loop acts as an EMI antenna for any signals running in that loop. E.G. if you have a computer and an amp, and both are connected to 'ground' (or 'earth', it's the same thing) through their power cables (using a 3-prong plug, which indicates it's earthed), then both are grounded. If you then connect an audio lead between the two, which has it's own ground connection, then there's a ground loop from your PCs power connection, through the PC, through the audio cable (which has a ground connection), through your amp, through the amps power plug, through the powerboard or whatever, then back to your PCs power plug. This whole loop will act like an antenna for any signal (like the audio going from your PC to your amp) that is part of the ground loop. Any noise from your CRT (and they give out a LOT of EMI noise) will be clearly audible in your speakers.

To stop this happening, you need to either break the loop, or make the resistance of the 'audio link' ground really really low.

To break the loop, you have to disconnect the ground in either the audio connection, or the power connection. Breaking the power connection is dangerous (i.e. using a 3-prong-to-2-prong or ground-lift adapter). It's illegal to do this in most developed countries except for the US (due to lax safety regulations). If you use a ground-lift power adapter, and your equipment breaks, you could be faced with a lethal voltage on any exposed metal. So DON'T do this! This leaves breaking the audio ground loop, which can be done by using a DI box, or by using Digital audio connections. Alternatively, you can use audio isolator adaptors which are sort of like DI boxes, but often have two isolation transformers instead of one, making them stereo.

The other option is to make the earth resistance of the audio connection as low as possible. This will decrease the 'antenna effect' on that connection. I used to do this when connecting my old Tascam US-428 (a USB interface) to my amp and my laptop at the same time. It would make a really nasty ground loop buzz, so I got a really thick length of cable (DC power cable, which has really low resistance), and soldered a "solder lug" onto each end. This is basically a little metal loop with a tag coming off it. You solder the cable onto the tag. Then I attached the lug on each end to a "chassis ground" point on both my amp and my US-428 using the screw that was already on the "chassis ground." "Chassis grounds" are basically just screws in the chassis of a piece of equipment. The chassis will normally be connected to ground, so this is a reliable point for grounding.

Phew I hope you make some sense out of this... it's a very frustrating problem to have, but once you understand the basic principles, you should be able to figure out a way around it.

what he said .. but:

get a TFT monitor.

I have 2 monitors a main 19" TFT and a CRT 17". I turn the crt off when recording guitar / bass.

then again, it's good to turn all your screens off when recording

Thanks for taking the time to point me in the right direction.