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HINTS & TIPS

 

DIGITAL TV SOUND

Name: Philip Teuten

Kit: Sony TV, DVD, AV receiver, Pace ITV Digital box

Problem: Philip keeps the TV muted and plays sound via his receiver and speakers. He has been very impressed with the sound from his system and recently decided to buy an ITV Digital box. While the picture is superb, Philip does not feel the sound is as good as when his source was a Panasonic VCR. In particular, he has had to take the sound source from the back of the Pace box using the stereo leads; otherwise it is out-of-sync with the picture. Philip uses SCART leads elsewhere.

 

EXPERT REPLY

Pictures and sound on ITV Digital are encoded using the MPEG 2 system (the same as DVD) and has the potential to be as good as normal NICAM stereo, which is presumably what Philip is getting from his Panasonic VCR. However, although NICAM is a digital sound system there's less compression and it undergoes less processing, which, incidentally, also accounts for the time difference between the analogue and digital signals. The soundtracks on ITV Digital channels also travel en-masse, as it were, as a 'multiplex' of signals containing the picture and sound information for several channels plus data and text for all of the other stuff we seem to need these days. What's more MPEG 2 encoding is 'dynamic' which means the proportion of the data stream allocated to each of the various components in the data stream constantly changes. Various other factors can also affect performance and whilst the digital TV signal is quite robust if Philip is living in a fringe reception area and the signal is weak then the error correction systems in the receiver will have to work harder and this could lead to a reduction in sound quality. Unfortunately there's nothing Philip can do about the way the signal is processed but he could investigate the possibility that he is getting a weak signal and if necessary, get a better aerial.

 

QUICK TIP

As any estate agent will tell you the three most important things when buying or selling a house are location, location and location. The same holds true for ITV Digital reception, a lot depends on where you live. If your picture is poor or unstable you can either move house or to try a new aerial, and get it installed as high as possible, the low power digital signals apparently do not bend or 'diffract' – following the contours of the earth's surface -- as well as analogue signals.

 

 

ASPECTS OF PLAYSTATION 2

Bryan Fryer

Kit: Sony PlayStation 2

Problem: Bryan is having problems with the DVD playback on his PlayStation 2. The picture appears to be stretched vertically on his 4:3 television. He has set the TV as a 4:3 on the main PS2 menu but it won't let him change from 16:9 on the DVD set-up menu. Is it this that's causing the problem and if it is why won't it let him change it? Also, which gives the best picture quality, S-Video or RGB? Can all of these go through the SCART connection?

 

EXPERT REPLY

This doesn't appear to be a common problem on the PS2 and indeed all of the samples we've tried allow you fiddle around with the Picture Size setting on the main configuration menu – used to set the display shape for games playback and the deeply buried DVD setup menu, which follows normal DVD player conventions with options for 16:9, 4:4 and 4:43 Pan and Scan. That would tend to suggest that Bryan's player has a problem and may need expert attention.

 

As for the differences in picture quality between S-Video and RGB, it really depends on the display device. On paper RGB should give the best results as the three colour signals undergo fewer stages of signal processing; colours should be sharper, purer and there should be less noise. However some TVs can produce an indifferent picture in RGB and in some cases picture controls have limited effect, or no effect at all on older models. Equally you can get good and not so good S-Video performance, in short if you have both options give them a try and see which one you prefer. The SCART connector format can be configured for both S-Video and RGB but not at the same time, this is usually a function on the setup menu (or a switch) on the source component. Also bear in mind that only 'fully-wired' or Type 'U' SCART cables can carry RGB and S-Video.

 

QUICK TIP

Playstation 2 is first and foremost a games console and DVD replay is very much a secondary feature, as anyone who has struggled with the microscopic menus and awkward controls – on the controller pad – will testify, but it can be made more tolerable. The best way to improve the PS2's DVD user friendliness is to get an infra-red remote control adaptor. They plug into one of the console's controller sockets and are now widely available for less than £20.

 

 

REGIONAL CONFLICT?

Name: Douglas Low

Kit:  Sony 36FS70 TV, chipped Sony 325 DVD

Problem: Previously, Douglas always used DVD's RGB output to view his discs (on Region Two and Region One). Having got the new TV, he decided to try to compare RGB and S-video performance. Both outputs gave excellent results on Region Two discs (RGB through AV-1 and S-video through AV-2). However, when playing Region One discs, whilst RGB is again excellent (through AV-1), outputting S-video from the player to both AV-2 and AV-3 gives almost colourless images – even the dedicated S-video terminal on the player gives a similar effect. Are Region One and S-Video are perhaps not compatible, or is the problem related to the chipping of the player or even the TV?

 

EXPERT REPLY

All things being equal an RGB connection between a DVD player and TV will usually look better, colours tend to be richer blacks are blacker, whites are brighter and the contrast range is broader and that's because the red green and blue video information the decoders inside the player extract from the disc are piped more or less directly into the TV's picture tube. S-Video, on the other hand is a two-part signal, the player first has to convert the virgin RGB information from the disc into a brightness or luminance (Y) component, and colour (C) component, send it down a pair of screen cables to the TV or display device and the TV then has to convert the Y and C components back into RGB signals, to drive the picture tube.

 

The differences between RGB and S-Video picture can sometimes be hard to spot on Region 2 recordings on some PAL TVs but if we now factor in differences in TV standards, then they can become more noticeable. Region 2 NTSC material will tend to look better in RGB as once again the video information isn't messed around with to anything like the same extent, whereas NTSC S-Video has to go through extra layers of processing in both the player and on the TV. It's not a problem; just use the signal system that gives the best results.    

 

 

 

THE IMPORTANCE OF IMPEDANCE

Name: Nathan

Kit: Sony DVP S735 DVD, Pioneer VSA E08 amp

Problem: Nathan has been offered a JM Lab Chorus speaker system. However the speakers have a nominal impedance of 8 ohms and a minimum impedance of 3.6 and 3 ohms. Nathan wonders what this means and wonders they would be OK to use with his amp as it is rated at 6 ohms?

 

EXPERT REPLY

Nathan should try and avoid getting too hung up on the numbers. The word 'nominal' means just that, it changes, in fact the impedance of a loudspeaker, which is a measurement of its resistance to an alternating current (AC) can vary slightly between identical models coming off the same production line and there are dips and peaks in the value according to a whole variety of factors including room temperature, humidity, the wires used to connect it to the amplifier, the frequency of the signal it is handling, the design of the enclosure and probably the colour of the wallpaper as well…

 

The key point to remember is that many amplifiers work most efficiently when the impedance of the speakers they are driving have an impedance of around 2 ohms.  Some are designed to work with a slightly higher value but the point is when speaker impedance falls below 2 ohms the amplifier can start to overheat and there's a risk of damage through overloading. When speaker impedance is higher than the amplifier's nominal rating power will be lost and performance may be compromised. The figures Nathan quotes indicate that the nominal impedance of the Chorus speakers is well inside the safe operating parameters of the Pioneer amp, and they can be used safely.

 

QUICK TIP

Cone type speakers usually have a nominal impedance of 8 ohms and high-frequency 'tweeters' are usually rated at 16 ohms, but the impedance of most speaker enclosures are either 4, 8 or 16 ohms, so why the discrepancy? It all depends on the way the speaker(s) inside are wired up, and things like crossover units, which are used to separate out the high and low frequency signals, and feed them to their respective drivers.  

 

 

DIGITAL DILEMMA

Name: Doug Mathie

Kit: none as yet

Problem: Doug currently has an analogue TV and wants to make the switch to digital in order to get the benefits of digital reception and also receive the free-to-air channels. He has no interest in paying any subscriptions charges though. Doug is also wary of using an integrated digital TV as he feels this severely limits his choice of sets. He wonders if buys a digital decoder set-top box but doesn't pay any subscriptions for a smart card, can he still receive the free-to-air channels? Also, Doug wonders what are the differences between digital terrestrial and satellite set-top boxes? Are they interchangeable?

 

 

EXPERT REPLY

Not surprisingly neither ITV Digital nor BSKYB are terribly keen on people acquiring digital TV services without a subscription. Basically it works like this. If you take out a subscription to a channel package – and this usually means signing up for a year's contract -- you get a set top decoder box at a heavily subsidised price, or free, or lent to you and in the case of satellite TV, the dish and installation may also be thrown in, or provided at a reduced rate. The deals and promos vary all the time but the starting point for both services is around a tenner a month for a basic subscription.

 

Satellite is the cheapest way to get the free-to-view channels (over 40 TV and 45 radio channels), there's a one-off installation fee (currently £100) and agree to have the set top box connected to your phone line. ITV Digital carries 21 free to air channels but won't supply you with a box without a subscription. Doug might be able to persuade a dealer to sell him one but we've heard the retail price is around £350. He may be able to find one second hand, or buy an IDTV. Terrestrial and satellite set-top boxes are not interchangeable however a low-cost decoder for free-to-air digital TV called Digital Television Adaptor (DTVA) has been developed by Pace and Xcom; it's likely to go into production well ahead of the proposed switch off of analogue TV services, which could be anytime between 2006 and 2010.

 

 

 

DELAYED REACTION

Name: Paul Reilly

Kit: Mission FS2-AV speakers, Sony STR-DB940 amp, Pioneer DV-636D DVD

Problem: Paul wonders if he were to put a pair of floor standing speakers in another room, would he end up with a delay in the sound if used simultaneously with the Missions? Paul would need to use approx. 20 metres of speaker cable from the amplifier to the speakers.

 

EXPERT REPLY

We get some odd letters… Clearly it all depends where Paul stands. Were he to be midway between the two sets of speakers then the sounds would reach his ears more or less simultaneously. If on the other hand he stood next to his new floor standing speakers, then he would hear the sound from them straight away, but the sound from the others would arrive a fraction of a second later. If you want to get really geeky we can calculate the time difference but we have to make some assumptions, namely that Paul's house is at or around sea level (standard atmospheric pressure and normal C02 concentrations), furthermore we'll work on the basis of an air temperature of 20 degrees C and a relative humidity of 30%, in which case the speed of sound calculator at: http://www.measure.demon.co.uk/Acoustics_Software/speed.html

informs us that it travels at 323.74 metres per second. Some simple sums on the HE office abacus reveals that the time it takes for sound to travel the 20 metres between Paul's Mission speakers and his ears (and this is very approximate) is 0.00617 seconds. No doubt there will those that will argue that such a time difference is not only significant but also detectable by the human ear but quite honestly we think Paul can rest easy and we can all get on with the rest of our lives…

 

 

BASS LIMITS

Name: Scott Thomson

Kit: Videologic DTS DigiTheatre home cinema system

Problem: Scott has this budget system in his bedroom to provide a ‘late night movie experience’ and has noticed a distinct rattle coming from the subwoofer during particularly bass heavy incidences. Is the limit of the system being reached? Scott is now on his third replacement, all of which demonstrated this problem. HE reviewed this kit in issue 78, and gave it a five star rating. Did your review push the system to its limits?

 

EXPERT REPLY

We always test equipment well beyond the normal call of duty, and our reviewer noted that the eight-inch driver on our sample did seem to have a relatively short throw, but it wasn't considered to be a problem under normal listening conditions – and that's what we're interested in – and the system as a whole performed well. Obviously you can make any speaker or sub distort and eventually crash the end stops, if you drive it hard enough, but that's not real world conditions, and it doesn’t prove anything.

 

From the sound of it Scott is trying to achieve the kind of cavernous bass effects that this particular system is not designed to deliver. Nevertheless it is not unknown for the components inside sub woofers to rattle, and they can certainly cause other things around them to vibrate, so it's always worth trying them in different positions. The Videologic DigiTheatre system works fine within the confines of a medium size living room or bedroom, but if Scott wants the kind of sub and amplifier that's capable of serious structural damage he's going to have to look elsewhere. 

 

 

DENON DOUBTS

Name: Alwyn Owen

Kit: Denon AVR-3802 AV amp, Sky Digibox

Problem: Alwyn has just bought the Denon 3802 and is very impressed with it and it was worth waiting for. However, Alwyn has learnt that the AVR-4802 can deal with dts 24/96 DVD-Audio but the 3802 can't. Is Denon offering a software upgrade for the 3802 and if so would it worth the effort given the paucity of compatible discs?

Also, Alwyn read that Pace has made a module to fit existing Sky digiboxes via the PCMCIA slot at the rear, which enables said digibox to extract and output Dolby Digital sound via optical/coax link. Is this true and are there any plans to market such a device? He has no plans to move over to Sky+.

 

EXPERT REPLY

It sounds as though Alwyn has been doing a bit of web surfing, according to our man at Denon the AVR-4802 is a US product costing $2500, and totally unrelated to the 3802. A European version of the 4802, called the AVR-A11SR, should be available about now for £1800, and it will be the first amp to ship with 24/96 dts. No upgrades are planned for the 3802, in fact this is quite a rare feature and usually only found on high-end kit, costing considerable more than the 3802. However, a dts 24/96 upgrade (hardware and software) is planned for the Denon AVC-A1SE, probably by early 2002.

 

The rumoured 5.1 upgrade for existing digiboxes is one of those things that is almost certainly technically possible but unlikely to happen. For one thing the market for such a device is likely to be relatively small; we suspect that the number of Sky viewers, signed up to the movie packages with 5.1 sound systems is not enough to warrant the production of such a device, or that it would be prohibitively expensive. Moreover, it's likely to take a year or so before the number of movies broadcast with 5.1 soundtracks makes the exercise worthwhile. It's quite possible that the next generation of digiboxes will have the facility and of course the option is there on Sky+ but because of the current lack of material it's not being touted as a top-line feature.

 

QUICK TIP

You know and love good old Dolby B and C tape de-hissing, thrill to the multi-channel surround sensations of Dolby Digital and now you can look forward to Dolby E. Relax, there's no new boxes for you to buy, Dolby E is a behind the scenes technology, used by broadcasters to encode up to 8 audio high quality audio channels, plus data, into a stereo digital soundtrack. This will make it a lot easier for them to quickly upgrade their systems to 5.1 Dolby Digital channel sound. 

 

 

 

TOSH TROUBLE

Name: Mark Williams

Kit: Toshiba MT1 projector, Yamaha DSP A3090 amp, Toshiba SD100 DVD player and an NTL digital STB

Problem: This one has everyone stumped, says Mark. His DVD player is connected to the projector via S-Video. The TV is run via composite video. He cannot leave the S-Video connected permanently, as it disables the composite lead and he can’t watch TV. The constant plugging and unplugging of the leads is resulting in trips to his local AV shop to replace broken cables. Switchboxes do not work. There is an input for a computer labelled RGB. Could this be used, Mark wonders.

 

EXPERT REPLY

According to the good people at Toshiba the explanation is that SD100 is an entry-level player and as such they would expect most users to only want to connect it to one display device at a time, hence the facility to switch between composite and S-Video... This seems like a rather spurious argument to us but the long and short of it is that there is nothing Mark can do about it at the player end, and it’s one of the other. However, all is not lost, if his aim is simply to drive two display devices simultaneously then it might be possible for him to ‘loop though’ a composite video output to the projector, through his TV. This is on the assumption that his TV is a fairly recent model with two or more SCART connectors. However, this would mean that the projector is only getting a composite video signal, rather than the higher quality S-Video signal, but on this type of setup it is unlikely that it will be that noticeable, if at all.

 

 

 

STARTING OUT

Name: Damian Wilkins

Kit: Sanyo Pro-Logic Widescreen 32inch TV, Samsung DVD player.

Problem: Damian would like to make the next jump to digital surround sound, but is new to this game. He feels that he wants to get a Dolby Digital or dts decoder, processor, decoder or amplifier. The trouble is he would like to know what all this means. Damian would like to have it so that he can “watch the DVD's with the 5.1 surround sound effect - aeroplanes flying across the room type thingy!!” He has a budget of around £300-£350 and hopes to negotiate the price down, so that means a RRP of around £400.

 

EXPERT REPLY

Damian has got the right idea and the next logical step is for him to upgrade to digital multi-channel surround but his budget is fairly modest and he must be realistic about his expectations. Dolby Digital and dts (Digital Theatre System) are both types of '5.1' surround sound system, originally developed for use in cinemas. Basically 5.1 means the soundtrack has five high quality 'full bandwidth' channels (right and left front stereo, centre-front dialogue, and right and left rear stereo surround) plus one narrow band channel that carries only low frequency bass sounds and effects. Technically Dolby Digital and dts are quite similar but Dolby Digital (formerly known as A-3) is part of the DVD format and most discs have it whereas dts is a fairly recent development and there are fewer recordings. However, it's not a huge problem and these days most devices (AV amps, DVD players etc) that have built-in 5.1 decoders can handle both types of soundtrack. 

 

Damian's best bet is a packaged system, which will include an AV amp with built-in Dolby Digital and dts decoders, plus a set of matching speakers, and preferably a sub-woofer as well (for those bass effects). Time to name names; given the size of his budget the Videologic Digitheatre DTS will give Damian the most bangs for his bucks and should provide him with a good introduction to the joys of digital surround.

 

 

GETTING STARTED 1 – DIGITAL TV SOUND QUALITY

The quality of digital terrestrial and satellite sound has occasionally and somewhat optimistically been compared with audio CD but it's a long way short of that. In fact the MPEG 2 audio system used by both Sky Digital and ITV Digital employs a bit rate that is around one tenth of that of CD. There are other considerations, digital TV sound is highly processed, both in the studio – as a hangover from the way analogue sound is handled -- and at various point along the transmission chain. What's more the data is liable to corruption and interference, which can result in audible 'artefacts' and even short breaks in transmission resulting in dropouts. Nevertheless, for all that digital TV sound is surprisingly good and with a strong signal such deficiencies as there are tend only to be noticeable when listening intently to music, and only then when the digi box hooked up to a decent hi-fi system and speakers – the audio systems in most stereo TVs can hide a multitude of sins…The most obvious effects of all of the processing is that higher frequency sounds and transients – drums and percussion and so on – lack the sharpness and clarity of CD.

 

GETTING STARTED 2 – A QUESTION OF STANDARDS

Differences in TV standards cause a lot of confusion when it comes to DVD so here's the low down. Ignoring for a moment Regional coding, (more in a moment), in most cases DVD players bought in the UK will be able to replay 525-line NTSC recordings on ordinary PAL televisions. The majority of players made in the last year or so either convert NTSC recordings into a 625-line PAL signal that can be viewed on any TV, or partially convert the signal, (Pseudo PAL or PAL 60), which again can be viewed on most recent PAL TVs. A few older players do not convert the signal at all and the result will be a black and white picture on a PAL TV. Several models also have the facility to replay a disc in it's 'native' format, which means you get a NTSC video signal, this can only be played on a multi-standard TV. Regional coding is a separate issue; this is a data 'flag' on the disc that tells the player whether or not it is allowed to play it and has nothing to do with TV standards. In case you are wondering Region 2 NTSC recordings do exist – Japan is also Region 2 -- and there are also a growing number of NTSC Region 0 (region free) discs.

 

 

---end---

 

Ó R. Maybury 2001, 0111

 

 

 

 

 

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