AudioMedia - October 2008 - (Page 50)

POWER FACT & FICTION > structure of your building can be difficult. By law, any metal pipes installed have to be electrically connected to the structure of the building and to Mother Earth herself – but do not rely on this, as the water and other pipes coming into a building are more often than not plastic, and only become copper piping after the water meter and main stop-cock. Another tell-tale sign of a poor earth is a reading of anything other than zero volts AC between neutral and earth, or between neutral and the structure of the building. If in doubt, get an electrician to test your supply and install a unified earth that connects all metal pipes, metal supports, walls, and anything else structural that can conduct electricity. values, state this in writing to your supply company, as they are legally obliged to keep well within those boundaries. Although all equipment is supposed to be able to cope with voltages up to (in Europe) it is definitely not good for them, and if you are suffering from mains supply well in excess of volts, it is best to use either a voltage regulator, or a UPS. When testing your mains, remember that most multimeters are pretty accurate, but the same cannot be said for some of the read-outs on power conditioners and surge protectors, and it is not unusual for these to be five or more volts out. Low voltages at the other end of the scale lead to higher s/n ratios in some (usually cheaper) types of studio equipment and instability in some digital boxes. Voltages had to drop to or lower for this to become a problem. subject to interruptions, you may need to look at feeding your audio equipment through an uninterrupted power supply (UPS). The three basic types are off-line, line-interactive, and in-line. The off-line variety does not interfere with the power supply and only takes over if the supply voltage falls below a certain value or fails altogether. Because this type can lead to computer crashes and even cause damage during the take-over phase, they are not suitable for recording studios. The line-interactive type of UPS is rather like a large variac with inverter back-up, powered by battery. These take care of over- and undervoltages, and the inverter springs to life if the power fails altogether. If all you worry about is power fluctuations and black-outs, then this is the type for you. The on-line UPS is a DC to AC converter running constantly from a set of batteries that are kept topped up from the mains supply. This is the type to have if working in very critical conditions, such as an operating theater, where perfectly regulated supply, free of any RFI, is needed. They are, however, far more expensive than line-interactive. Your multimeter will also be able to tell you what your mains supply voltage really is. In the EU it is supposed to be volts, but your supply company is allowed to vary that by up to . If the supply voltage falls outside the permitted Voltage Levels If you are having brown-outs (periods of lowvoltage supply) or worse still, your supply is UPS Deliver y THE SYMPHONY SYSTEM The Most Powerful Audio Workstation Available The Symphony System combines Apogee’s legendary X-Series and Rosetta Series converters with Apple’s revolutionary Mac Pro and Logic Pro audio workstation using the 32-channel Symphony PCI card. The addition of screened power cable made no difference in any of the cases tested. It made no difference whether the earth was good or bad and it made no difference whether the amount of RFI in the power supply was high or low. The addition of screened power cable had no effect on RFI levels, switching noise, or any equipment’s noise floor or mains hum levels. I called the supplier of these power cables and pointed out my results and a salesman told me, “We find that people with a technical background have greater difficulty hearing the benefits of our cables.” …I’ll leave it at that! M agic Cable BEST SOUNDING The most sonically advanced audio hardware interfaces combined with the most advanced music creation and production tool. HIGHEST PERFORMANCE 1.6 milliseconds at 96k and up to 192 simultaneous channels of audio. Introducing Logic Studio A suite of powerful, easy-to-use music creation and production tools, Logic Studio gives musicians everything they need to write, record, edit, mix and perform. GREATEST VALUE A fraction of the cost of popular card-based, DSP systems. Symphony PCIE Card 32-Channels of I/O per card & up to 96 channels per system. The Total Package When testing equipment that was of good standard and properly earthed for the effects of RFI, we did get RFI levels in V range in the power cable. When this happens in a working environment, far greater amounts of RFI are transmitted into the connected cables and the body of the equipment. Quantifying and trying to suppress such low levels of interference, when most unwanted noise is entering from just about everywhere else, would indeed be fool’s errand! Balanced power is extremely expensive when done properly and within the law. It does have specific applications, such as scientific laboratories and some operating theatres, and all connections and the continued usage have to be overseen by a qualified electrician, both in the US and within the EU. In some EU and US states, a government accredited certificate of safety is required annually. This is because balanced power, especially when used together with unbalanced power, or just incorrectly installed, can be very dangerous. Interference carried within the mains electrical supply does not seem to be the big problem that some would have us believe. Poor earthing and RFI carried as radio waves, entering either that poor earth or all the cables and equipment in your studio will always be a problem, easily solved the old fashioned way, with good earthing and good cabling. And if in any doubt about your earthing, call an electrician. ∫ Conclusions 50 AUDIO MEDIA OCTOBER 2008 http://www.sonic-distribution.com

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Audio Media - October 2008 Content Recording Post Broadcast Geofocus:�Portugal &�Spain What's Up UK IBC Report Microtech Geffel UM 930 Steinberg Cubase 4.5 ADK�Hamburg &�Vienna Final Cut: House of Fallen Lexicon PCM96 Review The Conch Awards Feature Sound Devices 788T Review Lexicon PCM96 Allen &�Heath Zed R16 Power: Fact & Fiction, PT.2 Product Sampler Plug-ins Video Guide AMSR Plasa Report Audio Technica IEM�M3 Rushes Live Mixing Techniques:�Bruce Johnston Drawmer 4x4 Kickbox

AudioMedia - October 2008

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