Power Rating Guide
Watts, VA And Power Factors
Often used but frequently misunderstood. The relationship between these is given as:
- Watts / VA = Power Factor
So How Does That Relate To Your SubStation² or Qube²?
Well transformers are rated in VA and as you can see from the equation above, this is not always the same as Watts. The problem occurs when the power factor moves away from one (1).
If the load is purely resistive, for example a light bulb, then the power factor would be 1. Therefore in this instance the VA figure will be the same as the Wattage. But if the load has either irregular current draw or an element of inductance or capacitance then the power factor will vary.
Most Hi-Fi products will convert the mains electricity into Direct Current and in doing so; the current demand from the mains will be fairly irregular. Large power amps with banks of large filter capacitors will be the worst offenders and their power factors may drop to 0.7 or even worse at full power. Let us assume that the consumption for the amplifier at full power is 1000 Watts and it has a power factor of 0.7 then the VA rating will be 1428VA. So you can see from this that the rating for the Isolation transformer would need to equal or better 1428VA not 1000VA.
Now very few products will give either the power factor or the VA rating so that is why we say to be generous with the rating of the Isolation transformer. Not only will this mean less chance of overload, but also it will result in more effective cleaning of the mains and therefore better sound. We recommend a 2:1 as a sensible middle ground. Therefore, with this in mind the 2K Qube² is conservatively designed for continuous use at the rated 2000 VA, so for best results operate nominally at around 1000 Watts.
As music is a very transient thing, power amplifiers generally idle at relatively low input powers but rest assured that the Qube² can supply power grossly over its 2000 VA rating for musically relative time scales.
In fact tests have showed that over 4000VA can be supplied with minimal compression!
The 4K Qube² will double the figures above and the 6K Qube² will triple them.
© 2008 ISOL-8 Teknologies Ltd. Tel: 020 8856 8856
www.intergage.co.uk
