Originally Posted by Matt Syson
If modern students manage to stay awake to about year 2 of high school where they are told about some of the essential 'laws' of electrical theory, Ohms Law, Faradays laws and so on they might begin to understand what is going on. You don't have to have a 'degree' in it unless you want to make a career of it. Just an overview is sufficient so you can avoid obvious pitfalls. I have done technical work in hundreds of studios across Europe and farther afield and don't remember seeing any with dedicated 'power balancing' transformers.
The worst studio for HUM was one in Germany where the desk was about 4 metres from a 11KV overhead single line cable for the railway. When trains went past the alteration in radiated field changed the colours and shifted the image on a CRT computer monitor. Yes there was some hum on the desk output, about 10dB worse than it should have been.
I have however been to many studios where the monitors hum (when I arrive) although recording out is fine, this is simply poor wiring practice.
Having worked in the past at many BBC and independent broadcasters I have never been aware of 'balanced power' for any of the studios although in the late 1980's isolation transformers were introduced as 'health and Safety' measures for 'Artistes' to use their own guitar amps where their equipment had not been fully tested for safety. This was an issue of DEATH and LIABILITY and not hum reduction.
I sorted a problem of hum in a basement studio in Tel Aviv. The problem was that the basement/bomb shelter was the basement of a multi-storie building and extended under the side walk of the street above.
Running parallel to the console's unbalanced bus bars was a massive power cable feeding current to the building. They had to contact the power company to have the cable re-routed.
I found it using a simple reel of equipment wire attached to the input of an oscilloscope. You could follow the path of the cable above the ceiling with that simple jig.
I've seen other hum issues in studios, all fixable with basic tools and a little imagination.
There's more muck on power lines these days and a filter will fix them but an isolating transformer? HF will sail straight through it!
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