You may have noticed that I am feeding a minimum of three component signals (two DVD players and an HDTV receiver) and sometimes four or more (an X-Box and/or a computer) into the two component inputs of my Sony VW10HT. I've received a lot of questions asking how I do this and the answer is that I use the component switching on my Denon 5700 for the two DVD players (currently a Sony DVP 9000ES and a Panasonic RP-91, both progressive scan players) and occasionally an inexpensive A/V switch (Radio Shack Part #15-1966) when I need additional component inputs.

When some people hear this they immediately question this practice since they are concerned with the bandwidth limitations of most component switches unless you go for big bucks. The fact of the matter is that component switching VIDEO signals is not as critical here as AUDIO signals would be and the best explanation of this is contained in a recent article from the good people at OUTLAW AUDIO on their web site. Here's what they have to say on the subject.

A FEW WORDS FROM THE EDITORIAL OUTLAW

July, 2001
Component Video Bandwidth

We're often asked what the bandwidth will be for the component video switching in the Model 950. We're finalizing the part selection right now, and we won't know for certain until we're able to actually run objective tests. However, our target goal is to have the end result somewhere between 40 MHz and 50 MHz per channel (Y/Pr/Pb).

We know that this will cause some comment, so we're going to explain ourselves upfront on this one. Regardless of what you may read elsewhere on the internet, or attempt to calculate by multiplying various aspects of the video system together, the plain fact often ignored by many posting messages in the various forums is that the Y/Pr/Pb signals are analog, not video. (In fact, if they were digital components they would be labeled as Y/Cr/Cb, but that's a story for another day.) While they may have been digitized at one point, when you deal with them at the output of a high definition set-top or a progressive scan DVD player, you are looking at analog signals.

Depending on the origination medium, these signals are governed by a series of SMPTE standards during the production process. (SMPTE 240M for the earlier cameras and systems with 1035 line limitations, SMPTE 274M for current 1080 systems, SMPTE 296M for 720P systems and SMPTE RP 160 as the Recommended Practice for "Three-Channel Parallel Analog Component High-Definition Interface". In the consumer electronics world, these connections are guided by the EIA-770A standard.

No matter which of these standards you look at, the specification for "nominal video bandwidth" is 30 MHz. NONE of the systems by which high definition programming is produced calls for bandwidth over that figure. The "RP" for the connection of "equipment operating with analog component HDTV signals" references itself back to the Standards, but specifically mentions a 30 MHz nominal video bandwidth figure as well (RP 160-1997, paragraph 7.2.1). Similarly, the consumer electronics industry's own standard also calls for 30 MHz in each of the Y/Pr/Pb channels.

Some might say that "more is better", but in this case it simply isn't true. We've consulted with a number respected engineers in the HDTV world, and they all agree that 40 or 50 MHz in the analog connection of HDTV signals is all that you need to want. Wider bandwidth in these connections may subject the system to possible RFI/EMI interference from a variety of sources. In other words, you'd find that you have "too much of a good thing". In audio there are some who say that wide bandwidth is appropriate, but in video all you will do is run the risk of having to deal in intrusion from a variety of unwanted signals.

The conclusion: Sure, we could easily design a switching system with 50, 100 or 200 MHz bandwidth, but there is no reason to do so. Spending money on components that deliver no perceptible benefit just to claim a higher figure than internationally recognized standards call for is just silly. The Outlaws like to have fun, but not at our customers' expense.

 

I was, like many people, reluctant to use the component switching on my receiver because of the opinion that bandwidth would somehow be compromised and when I only had two devices with component outputs this was not a concern. However with the addition of HDTV (see the separate section on this) and the occasional connection of a fourth or fifth component output device to my two component input VW10HT I needed a solution. Luckily when Outlaw Audio expressed their opinion in July, 2001 it coincided with the expansion of my HT component input needs. So, with nothing to lose but a little time, I connected both DVD players through the component switching of the DENON 5700 receiver to see what effect, if any, there would be in the quality of the picture.

After much comparison by viewing the pictures on the big screen (the larger the display the easier to see any flaws in the picture) I can state without reservation that I did not notice any difference between component video signals when connected directly to the projector or through the component switching device on the receiver. I've even looked at HDTV component output through the same devices and, even though HDTV has greater bandwidth requirements, there is no discernible difference between the two pathways. Granted, this is a visual comparison and not the result of a lot of test equipment. But to my way of thinking the eyes have it as far as the home theater visual experience is concerned and I'm perfectly happy with my setup.

I guess the Outlaws were right and I'm confident that video component switching with today's equipment will do the job.