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1:10 AM

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Tune Up: Capacitors

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Capacitors are used in most electronic products, and it’s common to see many of them populating a circuit board. These cylindrical devices store power the way a reservoir stores water. So when a circuit needs a bit of juice, the cap releases it. A capacitor is able to deliver power more rapidly than the car’s charging system because the power capacitor has a lower internal resistance, which allows it to quickly discharge.

In the early 1990s, car audio sound-off competitors started adding large capacitors to their sound systems to provide instantaneous power when peaks in a musical passage demanded it. Before long, car audio-specific capacitors became available to the masses, and now they are a common sight in most high-end systems Capacitors are rated in Farads, which is a measure of how much power they can store. The rule of thumb is to use 1 Farad of capacitance for every 1,000watts of power. So if you have a 500-watt system, you would need a 0.5-Farad capacitor.

Capacitors are available in Farad ratings ranging from 0.5 up to 40 for extremely high-powered systems, and vary in price from $75 for a 0.5-Farad cap to more than $500 for a large-Farad version. Besides Farad rating and shape, capacitors also differ in features, with some sporting built-in digital voltage meters and power-distribution blocks. You can buy a capacitor from most car audio retailers, and they’re available online from e-retailers such as Crutchfield (www.crutchfield.com).

You probably don’t need a capacitor if you have a modest system without a subwoofer, but you could probably use one if your system includes at least one subwoofer. If you have several amplifiers and multiple subwoofers, adding a cap or two can definitely improve your system’s performance. Whether you need a capacitor also depends on how much current your amplifiers draw from the vehicle’s charging system as well as the type of music you listen to. If you primarily listen to bass-heavy rap music and your headlights dim every time your system hits a bass note because of the strain on your car’s charging system, a capacitor could help. (You should also have your car’s electrical system checked to make sure it’s up to snuff, however.) Or if you think the total current draw of all of the amplifiers in your system starts to exceed the capacity of your car’s alternator, you’ll probably want to add a cap.

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7:50 PM

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Canon EOS 500D (Digital Rebel T1i / Kiss X3 Digital)

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Just 14 months after the launch of the EOS Rebel XSi (450D), Canon has unveiled its latest model, the Rebel T1i (500D). It's the fifth generation of Rebel and enters the market at a difficult time - in the midst of a global economic downturn and against the fiercest competition we've ever seen in the entry-level DSLR sector. So what has Canon done to make this latest model in the longest-established family in the sector live up to the edgy and exciting image implied by its US naming?

The 500D/T1i doesn't quite have to be the everyman camera that its predecessors were. The introduction of the Rebel XS (1000D) in June 2008 means the T1i no longer has to appeal to everybody who doesn't want to stretch to buying into the 50D class. As a result, the 450D was able to bulk up its feature set to include a selection of features that price-conscious shoppers don't necessarily realize they want, such as a larger viewfinder and spot metering. The result was probably the most complete Rebel we'd seen.


There's a full explanation of the differences between the 500D/T1i and it predecessor on the coming pages but, in general terms, it's a gentle re-working of the 450D. So you get the 15MP sensor much like the one that appears in the 50D, helping this to become the first entry-level DSLR to feature video (and 1080p HD video at that). You also get the lovely 920,000 dot VGA monitor that has been slowly working its way down most manufacturer's DSLR line-ups. There are a handful of other specification tweaks that come from the use of the latest Digic 4 processor but essentially this is most of a 50D stuffed into the familiar 450D body.


And, if the loss of the letter 'X' from the US name seems a bit disconcerting, you can comfort yourself with the knowledge that the Japanese market will still know it by the odd-to-European-ears 'Kiss X3 Digital.' For simplicity's sake, we'll refer to the 500D/T1i/Kiss X3 by the name 500D throughout the rest of the preview. (Source from dpreview.com)

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