Q&A # 223 - March 21, 2001

Staff

Q I've read recent press releases from Sony and Mitsubishi saying their next RPTVs will have the IEEE-1394 (FireWire) interface. Since I already own a Macintosh and Canon DV camcorder, I�m quite familiar with FireWire and have been interested in purchasing an HDTV that also has FireWire. Questions: (1) What will the benefit be to having FireWire in an RPTV? (2) Will I be able to directly view my camcorder's output on the HDTV via FireWire? Will I be able to send the Mac's computer display to the HDTV via FireWire? (3) If DVD players someday have FireWire, will there be a significant or small  performance improvement over today's players? (4) Which manufacturers are furthest along in their plans to build AV Receivers and DVD players, etc. with the FireWire interface?

A (1) Connection will supposedly be through a hAVI network (Home Audio Video Interoperability). This defined but currently not implemented standard can theoretically make interconnection of our AV systems drastically simpler. The goal is to get your system to the point that you will have one MPEG Video Decoder, one Audio decoder etc. rather than multiple decoders. In addition, with all components connected together using the hAVI standards, our current tabletop loaded with remote controls can go away. (2) In theory both of these are feasible solutions, although I'm not sure that your Mac would support display redirection via FireWire. I suppose that you could define a 2nd display as your HDTV, provided it was using a hAVI supported resolution, but that's just speculation on my part. (3) That depends on how much you spend on the MPEG video decoder -- which will become the differentiation factor. (4) Mitsubishi seems to be leading the charge for FireWire in the consumer electronics front. Sony, Panasonic, and Toshiba will be the 2nd wave. FireWire is not a panacea to all of our woes -- for instance, audio/video datastreams are designed for real time data flow, and FireWire is a packetized protocol. It remains to be seen how well a system connected together with FireWire will actually perform. It holds great promise, but it's too early to tell what will actually be delivered. Another potentially interesting technology is USB-2, which has similar bandwidth to FireWire. However no consumer electronics companies seem to be working with USB-2 as an A/V interconnection standard.

Q I was intrigued by your recommendation to one questioner that he use Radio Shack Gold cables. I have the Proceed DVD transport (PMDT) and a new Pureflat Panasonic TV with component video inputs. The PMDT has BNC connectors, and the TV has RCA connectors. I am presently using Radio Shack Gold cables and BNC to RCA adaptors for the component video interconnection as a temporary measure. The Radio Shack cables consist of 2 audio cables (L & R) and 1 video cable which came as a threesome. Given that the BNC to RCA adaptor probably represents an impedance mismatch (I don't even know if it is rated as 75 or 50 ohms or what ?), does it make sense to invest in higher quality component video cables? With the present cabling, the picture is certainly very good but not appreciably better than the S-Video connection which uses a good quality Monster S-Video cable.

A Yes, since you have BNC connectors on your player (BNC is 75 Ohms as standard), it would be a good idea to use cables that have BNC plugs rather than going through adapters, because the RCA plugs on the Radio Shack cables are likely to be less than 75 Ohms. They might be as low as 25 Ohms. Even if they were 75 Ohms, there is always some signal loss at every connection, including adapters. The lower impedances are OK for analog audio, but with the megahertz frequencies present in video signals, it is better to have 75 Ohms. Order a set of cables with BNC on one end and 75 Ohm RCA (Canare) on the other, from http://www.bettercables.com.  Brad Marcus, who owns the company, works out of his home, and sells only over the Internet, so the cost is not encumbered with dealers or warehouses. This also lets you order custom lengths with the specific connectors you want too. I asked him specifically about the component cables, and he said they are just about to come out with a brand new line which will be very lightweight.

Here is a picture of the set I have from Better Cables. Notice that the terminations are 75 Ohm RCA Canare, and the whole set is wrapped with a jacket to keep them all together.

Q I have a Sony receiver TA-VA80ES (known as STR-DA80ES in the US, without the tuner). I have read the manual and it says that the oversampling frequency accepted by the receiver is max at 48 kHz, and anything higher will not work. I am shopping for a DVD player, and I can't find anything with less than 96 kHz oversampling. Can you help me with this? I like my receiver since it's one of Sony's ES series and have no problem with it so far.

A I think what your receiver instruction manual is saying is that it will not upsample any input that is higher than 48 kHz, namely 96 kHz. However, if it will upsample an incoming 48 kHz signal to 96 kHz, it would need a 96 kHz DAC. So, I suspect you can input the 96 kHz digital signal, but it just won't upsample it from there. If your DVD player does have upsampling, I think it probably then performs D to A, and outputs the analog signal. The digital signal output is probably still 48 kHz in the case of DD and DTS.

Q Do you know of a device that will allow me to switch between two sets of component video inputs? My preamp does not perform component video switching.

A Here are some links to component video switchers:  http://208.149.133.207/hdtvgbr.html    http://www.extron.com/product/product.asp?id=sw6cs    http://www.tura.se/videopro/kramer/grupp2/vs2053.html    http://www.onecall.com/ProductDisplay.mpt?ShowFNS=1&ProductID=9563.

Q I have recently set up my home theater using a Denon Receiver/Digital Processor with built-in decoder, five Denon speakers, a Toshiba Colorstream DVD, and a Phillips VCR (the only one I found with an S-Video connection). My Denon Receiver has both an optical input and a coaxial digital input. I have the DVD player hooked up to the coaxial cable. So the Denon Receiver has the optical connection open, right? I have recently added a Marantz laserdisc player with an optical output and I am trying to set this up to the optical connection on the receiver. But I am having problem getting the sound to work on the laserdisc player using the optical (Radio Shack) Toslink cable. Is it an either/or situation on these two connections? The Denon has a place where I can tell it what is hooked to the optical and what is hooked to the coaxial, but if I try to tell it DVD on both, it won't accept it, and if I try to say, coaxial for DVD, and say "CD" for the laserdisc player, I still cannot get sound. (The Denon does not have a choice for LDP.) I finally just hooked up the sound of the laserdisc with analog coax (thereby getting the stereo sound), but my question is, is it possible to use both the digital connections in the way I have described, should I keep trying, or is it not possible?

A Usually with a receiver having this type of input setup, there is a digital coax and optical connection for each of the digital inputs. You choose one or the other and tell the receiver which connector (coax or optical) you are using for each input. Some of them will automatically detect the type of input, and some will default to coax or optical if you also have analog stereo connections at that input. For laserdiscs, DD has to be taken from the AC-3 RF coax jack, but at least two channel stereo should still be coming from the optical jack. Try disconnecting the DVD player coax digital cable from the receiver and selecting optical input. If you get some sound, then your problem is a conflict of using both digital input jacks at the same time. If still no sound, then the problem is something else.

Q I recently purchased a 53'' projector TV and was wondering if there was a minimum distance that should be kept between the TV and my tower speakers which are unshielded.

A The electronics for a projection TV are in the base, so that is the critical area. In my experience, unshielded speakers should be no closer than about 18". If they are too close, you will see a purplish color at the edges of the picture.

Q What is keystone correction in video?

A This refers to the fact that most video projectors are set up so that they are projecting at an angle (upward or downward) towards the screen rather than straight at the screen. The resulting image is trapezoidal because the top and bottom of the screen are unequal distances from the projector lens. Keystone correction changes the shape of the image on the CRT, LCD, or DLP panels so that it has parallel sides on the screen. Although keystone correction will straighten out the shape, it does not correct for focal points being unequal at the top and bottom, nor would it compensate for differences in brightness at the top and bottom. You are throwing out some of the resolution too, because the correction reduces the amount of CRT, LCD, or DLP panel area that is used for the image. So, a projector works best if pointed straight at the screen, but this is not very often convenient.

Q I have recently purchased a Pioneer Elite PRO-610 HD Rear Projection Television and with the package they gave me a great deal on a Pioneer DVD DV-38A. I already own a Yamaha V995 Receiver and a set of PSB Stratus Gold Surround Sound Speakers. Because I have already blown most of my purchasing money, what receiver would you recommend to run my Home Theater? They have offered to let me have the Pioneer VSX-39TX Receiver for a good price, but is it really any better than the Yamaha I already own? What receiver would you recommend around $2,000 to run this system? Could you give me some options?.

A The 995 is an excellent receiver, so if you really want to spend money, then get an outboard five-channel power amplifier, such as the Rotel RMB-1095, which will give you 200 watts per channel. Other than that, you are fine as is.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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