Articles and whitepapers

Making a Case for Advanced AC Power Conditioning for AV

By Garth Powell, Furman Sound

'Isn't my plastic AC strip good enough for my electronic rack or cabinet?'

'I don't have any detectable hum or rolling bars in my video, so my AC power is OK, isn't it?'

'My conditioner has a connected equipment warranty, so I'll never have power problems, right?'

WRONG!

Today's electronic circuits are more sophisticated than ever, and their susceptibility to AC line problems is far greater. Add to this the fact that today's AC mains supply is extremely noisy and the power grid is frequently taxed, and we have a recipe for component failure, or at the very least, poorly-functioning equipment with unreliable behaviour.

Graph showing the dramatic increase in the percentage of noise on the AC line against time

Most AC strips feature inexpensive surge suppression devices that are designed to 'sacrifice' themselves when exposed to sustained over-voltage conditions or transient voltage spikes. Although they generally save the equipment downstream, the unit itself must be serviced. Your system will be either non-operational, or at best, unprotected until the damaged AC strip is replaced.

Remember too that transient voltage spikes are not just present during lightning storms. Your local power utility sends countless spikes through the AC wiring each week. This is due to the necessary switching of one transformer or supply to another throughout the day to adjust for peak demand. Though not as severe as a direct lightening hit, these voltage spikes have a devastating cumulative effect on most electronics.

Advanced Transient Voltage Surge Suppression

Audio/video professionals cannot accept down time, corrupted data, or unreliability, and today's home theatre contractor, installer, or retailer should not either. It is for that reason that a transient voltage surge suppression system such as SMP+ (series multi-stage transient voltage suppression), is the best choice for critical home theatre/audiophile applications. With SMP+ there is virtually no down time. In fact, these circuits can typically handle multiple 6000V and 3000A pulses without sustaining any damage! This is far beyond the demands placed on generic surge suppressors.

One of the secrets of SMP+ circuitry is its ability to siphon off much of the offending transient voltage spike, so that the power clamping devices do not have the burden of absorbing all of the energy and impact on their own. Typical surge suppressors are like an outstretched spring with a bullet headed for it. The key to Furman Sound SMP+ suppression system for example, is that the severity of the offending voltage spike is critically damped, so that the overall energy level is reduced to a fraction of what the clamping devices can handle. So, like a well tuned shock absorber, the SMP+ circuit protects itself as well as the connected equipment.

The Furman PL-PRO DE II 230 Volt Power Conditioner

Sustained Over Voltage Conditions

Many surge suppression devices will not be able to protect equipment from sustained over voltages. This condition is more dangerous and damaging to home theatre components, and can occur for many reasons. A power pole may be damaged during a storm or accident, or in many countries, lost or intermittent neutral wiring of a multizone system can result in a sudden connection well in excess of 410VAC. This will result in destroyed equipment, or at best, a destroyed surge suppression system. In either event, equipment servicing is required.

To escape this problem, insist on a surge suppressor with Extreme Voltage Shutdown (EVS). EVS circuits monitor the incoming voltage, and once the voltage has risen approximately 15% above nominal, they trigger a power relay to open, thus cutting the supply to all connected components and critical circuits.

Filtering AC Power - Maximizing Home Theatre Performance

In the past, AC filtering was considered a relatively small concern. As long as pops, crackle, or a local radio station was not picked up by your components' power supply, very basic filtering was sufficient. This is no longer true. AC noise is far greater in both amplitude and bandwidth than ever before. When it couples into critical circuits, it masks and distorts low-level information, and it may create data corruption and losses as well. This is due in part to the widening popularity of switching power supplies, and the harmonics they back-feed into our AC power mains.

Today's AC power filters must have far greater efficiency, and cover a much broader bandwidth than ever before. Simply put, the AC noise that is coupled into your components' circuitry may be higher in strength than much of the low-level signals your equipment is attempting to reproduce. If this occurs, a masking effect will certainly take place. This is key, as high resolution audio and video is defined by its ability to accurately reproduce complex low-level signals!

In the real world, sensitive electronics represent a complex load. Unfortunately, traditional AC filter/conditioners have been designed for unrealistic laboratory conditions. Prior technologies could actually harm audio and video performance more than help, due to the resonant peaking of their antiquated, nonlinear designs.

A filter that is nonlinear will sound and look discordant because of the way we hear and see. You cannot lower noise in one octave - thereby unveiling far more signal information - only to increase the noise an octave away and, further, dramatically reduce noise 1/2 octave from there. This is akin to a poor job of audio equalizing, a bad loudspeaker crossover design, or vivid reds and greens with horrible blacks and yellows in a video presentation.

Clearly, an advanced AC noise filter must have linear filtering, and cover the widest frequency bandwidth possible. By doing so, you will be assured peak performance from your home theatre equipment.

Conclusion

There are many other considerations for advanced power management such as Power Factor Correction, Uninterruptible Power Supplies and Voltage Regulation, but what must be understood is that the sensitivity and sophistication of today's electronic circuits require serious AC power conditioning. Anything less is too costly to consider, and will limit the performance that your clients demand.

Garth Powell is the Senior Product Designer for Furman Sound USA, manufacturer of audio and video signal processors and AC power conditioning and distribution products.

www.furmansound.com