I realise this is somewhat off topic but wonder if somebody would be kind enough to help me out with some advice.
I am getting a bit of speaker hum that seems to be connected with the mass of cables, transformers, etc lying in a tangled mess behind my desk. That is to say if I move the cabling around I can make the noise increase or decrease but I have been unable to entirely eradicate it.
I am wondering whether I can eliminate it by hooking my active speakers up with a balanced lead, but the trouble is my soundcard only supplies unbalanced, and my question is what would I need to do to make that connection work? Is it purely a question of finding the right cable/connector or would I need something like a DI box?
First thing I would check is the actual connectors, both on the sound card and on the speakers. I am assuming that both are mini-phone (3.5mm) connectors. Try wiggling the plug in it’s socket, or (with the volume on the speakers turned way down) unplug and replug the connector several times (the wiping action will usually remove any small amount of corrosion that may have built up.
If that fails then yes, carefully untangle the wires. The problem could be the speaker feed passing too close to the power brick or wrapped around a power cord for several turns.
Do the speakers have a 3-prong power plug (with ground)? If so are they plugged into the same outlet as the computer or a different one. If yes then try to get them plugged into the same outlet, or plug strip. Another option is to use a 3-prong to 2-prong adapter to isolate the speakers from the house ground.
If the speakers have a 2-pin plug or wall wart, try reversing the plug in the socket (if it will let you).
Have tried the things you mention, and the problem undoubtedly is that the the immediate area around my desk contains cabling for 2xdesktops & 1x laptop with docking station connected to a kvm switch with extra leads for another, 2 x LCD panels, 3 active speakers, printer, router, modem, USB hub and myriad of connected peripherals, midi, audio input, passive audio out attenuator, passive audio source switch, etc, etc.
I installed a UPS a few weeks ago which took me almost half a day untangling and identifying wires, and it is now as good as it gets without ripping the whole thing out which is not going to happen.
Therefore I was hoping for a quick fix via a balanced connection.
Start with the processor receiver to determine if the hum/buzz is source-related or due to a ground loop occurring after the amplification stage
Note any recent changes to the system that brought on this problem. Chances are, you can more easily isolate a problem if it just starting with the addition of a new piece of equipment.
What can you do quickly and easily to isolate or identify the problem and point to the proper solution (i.e. unplugging the cable from the wall to see if the Cable TV is the source of a ground loop.)
One other test to eliminate your receiver or processor is to see if the hum changes based on what input you have selected (DVD player, Cable TV, etc.) Does the hum change or go away when selecting a different input? No? Then your problem is occurring at a later stage in the system (most likely a ground loop caused by the addition of an amplifier or powered subwoofer with a 3-prong power cable.)