Q&A # 280 - March 31, 2002

Staff

Q I have noticed that a small company named Tripath Technologies is winning contracts with big players like Sony, Denon, Philips, and many others in both Plasma TVs and Home Theater products. They make Digital Amplifiers that cut way down on the heat produced in amplification. The product is also very small in size. Can you tell me if there is a major change in store for us in the way of audio amplification (in terms of new products)? I would like your opinion of their amplifier product.

A They look good on paper, but the real test will be in the listening. Digital amplifiers are indeed in our future. It is taking a long time to get the bugs worked out such that they function well throughout the entire audio spectrum. Right now, they are quite common in powered subwoofers, because digital amplifiers work great at low frequencies. Tripath appears to use very high switching frequencies (1.5 MHz), which is much higher than previous designs. That may be the key to their technology. Obviously they are not going to talk very much right now about the details of how their products work, so we will just have to wait until components arrive for testing. They emphasize the value of their technology is cutting costs, so the units will probably show up first in mass market receivers and automobile hi-fi systems.

Q How much difference is there between preamplifiers in terms of the types of harmonic distortion?

A There is quite a bit of difference. Here are two spectra I (JEJ) took from two different products. One was a mass market receiver and the other a Parasound P/SP-1000 Preamp/Processor. I input a 1 kHz sine wave, and increased the volume until the harmonic peaks were very evident. Notice that with the mass market receiver, the third harmonic (3) is larger than the second (2), the fifth is larger than the fourth, and the seventh is larger than the sixth. This means the odd-ordered harmonics were the strongest, and this causes the sound to be very harsh. The higher upper harmonics are probably due to using lots of negative feedback. These upper harmonics are particularly irritating to listen to. With the Parasound, the second harmonic (2) is larger than the third (3), the fourth is larger than the fifth, and the sixth is larger than the seventh. This means the even-ordered harmonics were the strongest, and this would produce a less harsh sound. Of course, both products at this amount of distortion would not be tolerable to listen to, but I drove them into this high distortion to make the harmonics more easily discernible on the graphs. Note, however, that with the Parasound, the 60 Hz peak associated with the AC supply, along with several of its harmonics, are apparent (green arrows). This means the power supply could use better filtering. These AC peaks would manifest themselves as more hum. The noise floor of the Parasound is also a little higher than the mass market product, and would manifest itself as more hiss.

Here are some further spectra to show the differences between the receiver and dedicated preamp.

Q Great site!!! Absolutely, one of the best sources for unbiased A/V information anywhere.

I do have a comment for one of your answers to a question though. A reader asked about the different movie modes for a direct view Sony, and the following answer was provided:

A. "There should be memories for each of the modes, so that settings made in one mode, e.g., movie, will not affect the settings made in the other modes. Otherwise, there would be no point to having three modes. However, if you use Ovation to calibrate the three modes, they will all look the same. They are basically just three memory banks to store whatever settings you like for different situations. So, use Ovation for the one mode, such as Movie, and then set the other modes by eye, for watching at night, or one for daytime satellite, one for night time satellite, and one for DVD watching."

Actually, there are sometimes dramatic different service mode parameters for the different modes (i.e., SVM is disabled in Movie and Pro modes).  There is enough of a difference that if you set each of the four different picture modes to the exact same user settings for contrast, brightness, color saturation, sharpness, tint, and color temperature, you will still have a noticeably different display in switching between the different picture modes.

A Thanks for the info. Sometimes I yearn for the days when TVs just had on, off, channel, and volume.

Q  I have a Sony KV-27FV17 TV and I wanted to know if a progressive scan DVD player with component video output (Panasonic RP-56) will give a better picture than a player without progressive scanning using my TV? I know you need an HDTV to view progressive scanning, but if I don't have an HDTV and I use a progressive scanning player will I be able to view a DVD with the switch set to progressive or will it only work with it set to interlaced? If the switch has to be set to interlaced, will the picture be better than if it was a regular DVD player w/o progressive scan?

A Progressive scan will only work with digital TVs that are capable of displaying 31.5 kHz scanning (NTSC is 15.75 kHz). If your TV is not digital (not HDTV), it will not display the signal input from a progressive scan DVD player in progressive scan mode. In interlaced mode, the image will be the same as a DVD player that only has interlaced outputs. However, that does not mean you should specifically look for an interlaced output-only player. The RP-56 is an excellent DVD player, and it does not have the chroma bug.

Q When I press input on my 32" JVC television, it's a steady blue colour. When I turn on my Toshiba SD 5700 DVD player, sometimes severe shadows jump around left right up and down. Circles are all over but all the time a one inch line moves from right to left. They are under warranty but nobody knows what it is this is. It's the 4th time I have changed my DVD player.

A This will happen if you have your DVD player set to output progressive scan, and your TV only handles interlaced inputs. The Toshiba remote control has a button for changing back and forth from progressive to interlaced output. On some Toshiba players, there is also a slider switch on the back that you have to set for interlaced or progressive.

Q What is the time table for the "Blue Laser" DVD players to hit the consumer market? I am waiting to purchase the new Denon 3800, but do not know if this is a wise decision if it will be obsolete in a year.

A Blue laser technology has already been developed but will only really be pertinent to HD-DVD (High Definition DVDs). It will allow 50 GB to be on a DVD, which is plenty of room for high def movies. Problems at this point include the fact that the crystal (gallium nitride) that is used to produce the blue laser light deteriorates faster (200 hundred hours usage) than the red laser crystals in our current players (10,000 hours usage). Also, if you think Hollywood is paranoid now, wait until high def DVD gets here. I suspect we won't see HD-DVD for five years. Buy your Denon 3800.

Q I just acquired a S-VHS VCR. I am using it exclusively to archive programs from my TiVo (and to play back tapes). If I only use the TiVo's composite video output to the composite video input of the VCR (i.e., I don't use S-Video), would I get better recordings (and playback) if I (1) record in S-VHS mode (a selectable setting on the VCR); (2) use S-VHS tapes instead of VHS tapes; or (3) use the S-Video output of the VCR to the A/V receiver (instead of composite video). Of the 3 choices, in what order would you consider them to have the greatest impact, if at all, on video quality?

You're probably wondering why I just don't use the S-Video output of the TiVo to the S-Video input of the VCR. Right now I have the TiVo S-Video output (there is only one) going directly to the A/V receiver. As I only will archive tapes sporadically, I'm afraid that if I route the TiVo S-Video through the VCR S-Video and then to the A/V receiver that I will noticeably degrade the TiVo signal. Am I correct in that assumption about degrading the signal?

A First, let's note that the resolution through composite will be the same as with S-Video, but with S-Video, the color quality will be better and you won't have dot crawl. Secondly, each time you go through a plug and a jack (at the VCR or at the receiver), no matter how good the bandwidth, there will be at least a small amount of signal degradation.  The way you have things now seems the best under the circumstances. Assuming your receiver does not have more than one S-Video out, you could use a switcher or distributor to send S-Video out from your receiver to both your TV and your VCR. Such components are sold by companies like SmartHome (http://www.smarthome.com/videodist.html).

Q In your recent review of the Plus Piano HE-3100, John E. Johnson Jr. states the Piano's 848x600 chip in 16x9 mode cannot fully resolve the vertical resolution of DVD. And that the image has to be scaled down to 450 lines (compared to the DVD standard of 480). From what I have been able to gather, this would be true IF the chip produced only a resolution of 800x600. Because the Piano has a dual-mode chip which enables it to fully reproduce 4x3 material (in 800x600) AND 16x9 DVD material (in 848x600) in their native resolutions, John Johnson's statement about the inability to reproduce the full resolution of DVD is false. The benefits of the dual mode chip in the Piano have been mentioned in several articles and other reviews. Did your review miss something, or did I?

A The Piano's chip is 4:3, and the dual mode lets the chip show 4:3 in two modes as shown below. One is the inner 4:3 (blue with yellow numbers), which Piano calls "Real", and one is the outer 4:3 (green with black numbers), which Piano calls "Full". The Full setting uses 800 x 600 pixels. Letterboxed movies, such as 16:9 are shown in the area outlined by the red with yellow numbers (including the blue with yellow numbers too, of course). 16:9 is not shown on the full chip because the chip is 4:3. So, for widescreen movies, the height is reduced accordingly, even though the width is still out to the left and right sides as it is with "Full" 4:3. Therefore, with widescreen DVDs (16:9 and 2.35:1), there are far less than the 600 pixels of the full chip height showing the image on the screen, less than 480 since the 16:9 mode is not using the entire 848 pixel width. Since essentially all movies these days are 16:9 or 2.35:1, I generalized. Old films (pre-1953) on DVD at 4:3, shown with the Piano set at "Full", would of course have full resolution. By the way, 848 x 600 is 1.41:1, not 16:9, which is 1.78:1.

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