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Name Andrew Mathias

Kit Philips 32PW9616, Jamo Centre 200

Problem Andrew’s Jamo Centre channel is precariously perched on top of his Philips TV. He would prefer to have a less unsightly position for the centre, but the space under the set is already full and the Jamo Centre is too large to fit below the TV anyway. Could he use two small speakers for the centre channel and put them either side of the VCR? Andrew has a pair of spare KEF Coda speakers and wonders how to wire these up in place of the Jamo.


Expert Reply

The first thing that comes to mind is has Andrew given up with the TV's built-in centre speaker? Admittedly it's not very large, or especially loud, and it's not going to win any prizes for sonic excellence but in the normal course of events – handling centre channel dialogue -- it's not given anything particularly challenging to do, and it is in exactly the right place. If Andrew has tried and dismissed that option he should still pursue the central location, even if that means moving things around, or making some small sacrifices to appearance. It may be possible to jiggle a pair of speakers either side of the TV to produce an image that's directly in front of the screen but it will never sound as focused as the output from a single dedicated speaker. There are plenty of options, it sounds as though the Jamo speaker was doing its job, but it wobbles a bit and doesn't look very smart, so why not mount the speaker on the wall or whatever is behind the TV at or just above screen height?  The space under the TV is full, Andrew can make room, move one or more boxes or whatever is there to another location. Andrew has come this far and it's worth making some small sacrifices to get the best sound!



Name Mike Jeffries

Kit Pioneer 636D DVD player; Denon AVD2000 decoder; Yamaha DSP-E492 processor, Mission 75as sub.

Problem Mike’s partner purchased the DVD player as an upgrade to use the built-in dts decoder. However, Mike is not happy with the bass he gets from dts, as he finds the sub barely comes alive compared to Dolby Digital as played through the Denon decoder. He noticed that the old decoder does DD duties much better than the player's in-built decoder so he wonders if the player's decoders (both DD and dts) lack bass? Are there any adjustments Mike can do to the DVD to bring it up to the same standard as the Denon, without the expense of a new decoder?


Expert Reply

It would have been helpful to know what recordings Mike is using for his comparisons. We have noticed some quite significant differences between dts and Dolby Digital soundtracks on otherwise identical recordings, which suggests there can be inconsistencies in the mastering and transfer processes. However, the most noticeable difference between dts and Dolby Digital is usually the superior bass rendition of the former, so assuming that we're not talking about some rogue recordings, and since the only elements in this setup to change is the 5.1 decoder and the connection to the Mission sub the obvious conclusion to be drawn is that the sub output on the Pioneer player is not pulling its weight or there's something wrong with it. The player got a clean bill of health as far as bass output was concerned when we reviewed it last year, so it's possible Mike's one has a fault or needs tweaking. In any event he should go back and check the blindingly obvious things on the player's setup menus. The only other possibility – and this is a bit of a long shot -- is that Mike has the bass channel output on the Denon decoder wound up really high making the Pioneer output sound more shallow than it actually is.



Name Ashley Janes

Kit Yamaha RX-V795RDS receiver

Problem When the Yamaha amp is taken off standby while all other electrical components are turned off Ashley get a slight humming noise in the rear speakers. The humming can increase slightly if high-power electrical components (TV, washing machine etc.) are on at the same time. This humming only appears through the rear speakers. Andrew wonders if this is a problem with the amplifier or the mains itself and how it can be corrected.


Expert Reply

In fact it's not that unusual, especially when the rear channel levels have been set high, which it true of many home cinema systems. There's a great temptation to have the rear channel booming out all of the time but that's not how surround sound is supposed to be. The rear channels should be in the background most of the time and when they come in hard the effect is all the more dramatic. If Ashley goes back into his system's setup and adjusts the levels so that all channels sound equally loud from the listening position he may well find that the humming disappears. If not then the hum is almost certainly coming from nearby mains appliances or cabling and the most likely entry/pickup point is the rear channel speaker cables as theses are the longest. As a first step Ashley can try re-routing the cables away from skirting boards any mains sockets or under floor wiring. The cabling to the source components is another way mains hum can get into a system, so he should check all the plugs and socket, at the very least he should unplug and reseat them all in case the connections have started to deteriorate. It's worth earthing the amplifier's casework and that of any other connected components and finally he can try repositioning the amplifier away from any other devices.



Name Charles Khayat

Kit Sony STR-DB930 receiver, M&K 750THX speaker system

Problem In Charles’s system, the front and centre speakers have a nominal impedance of four ohms while the surrounds are eight ohm impedance. Can you tell me what ‘nominal impedance’ is, and whether the impedance selector on the back of the amp should be set to four or eight ohms?


Expert Reply

Nominal in this context simply means 'about'… In other words the impedance of the speakers is probably 4 ohms but it might be a little bit more or it could even be a little bit less. Most modern amplifiers are well protected against a major impedance mis-match or even a complete short circuit so Charles can safely try both settings on his amplifier. However, since the front and centre channels are going to do most of the work and they are rated at 4 ohms it's a good idea to try this setting first as this should provide the best match and it should in theory give the best sound. As an aside it is worth pointing out that Charles is not using his M&K speakers under absolutely ideal conditions. They are THX Select rated and designed to driven fairly hard so they are well suited to amps with power outputs in the 150 to 200 watt range. The Sony amp, good though it is only pushing out around 110 watts at full whack, which is barely enough to get the M&Ks out of second gear. They should start to come alive with something a little more substantial, preferably also THX rated.




Name Cameron Payne

Kit n/a

Problem Cameron wonders what video standard is used in Russia. He has read that VCR is quite a new technology to Russian people and hopes that PAL is the standard in Russia and England alike.


Expert Reply

VHS video recorders have been available in Russia and the former Union for almost as long as the West. Needless to say that for much of that time they were expensive luxury goods, inevitably few were sold and until the break up of the Soviet Union in 1991 servicing and spares were difficult to come by. Russia and most former Eastern bloc countries use the SECAM colour television system, the same as that used in France. The choice of system was allegedly political. The story goes that when the USSR was planning the introduction of colour TV in the mid 1960s – remember this was at the height of the Cold War -- it was thought expedient to use an existing system, rather than go to the expense of developing one of their own. However, the choice was between the NTSC system developed by the Americans, PAL, which was developed in Germany, or the French SECAM system, and since Russia had no particular gripe with the French, at least not recently, SECAM won the day. PAL and SECAM are quite closely related (allegedly they are just sufficiently different to avoid patent infringement, but that's another story…), and SECAM tapes will usually play on PAL VCRs, and vice-versa, but with a black and white picture.




Name Dorothy Jones

Kit Panasonic TV, Pace digibox, JVC S-VHS video, Sony DVD and Surround sound system

Problem Dorothy wants to know how to connect all this kit together, ideally using SCARTs where possible. A friend mentioned ‘daisy chains’ what does ‘daisy chaining’ mean and how does she connect the surround sound system (which doesn’t have a SCART socket) to the rest of the system (that does)?


Expert Reply

'Daisy Chaining' is a facility of the SCART connector system. Basically it means that AV devices  -- like VCRs and satellite receivers – with two SCART sockets can be connected together by a SCART to SCART cable, 'in line' as it were, and only one of them needs to be connected to the TV. The obvious benefit is that two devices can share one socket, which can be a distinct advantage when you may have three or more devices that plug into the TV, but only two (or even one) back panel SCART socket. It's effectively self-regulating and the AV output from the first device in the chain is displayed, or if that's switched off, the next one along takes over. As for Dorothy's system, (assuming that her TV has at least two SCART sockets), the fly in the ointment is the S-VHS VCR. Ideally that should connect to the TV using the S-Video connector, however, unless she actually watches S-VHS recordings, made on a S-VHS-C camcorder, it would be better to use it for the DVD player. However, if one of the TV's SCARTs can be configured for RGB or S-Video the DVD player can use that and the digibox can use the other SCART socket. The stereo audio outputs from the VCR and digibox connect by phono cable to the respective inputs on the surround sound system. The DVD player should connect via an optical or coaxial connector to the surround sound system (if it has a Dolby Digital/dts decoder) or another stereo phono connection, if it's a Dolby Pro Logic type. 



Name Nicolas

Kit n/a

Problem Nicolas wants to play both PAL and NTSC signals on his TV, but does not want any conversion. Most sets play NTSC as PAL-60. Nicolas wonders if there are any TV sets that play pure PAL and NTSC and if not, is it better to convert NTSC to PAL or vice versa? Also, Nicolas asks, is there any way to watch European satellite channels in America?


Expert Reply

Quite a few high-end home cinema TVs have the facility to display so-called 'raw' NTSC signals via one or more of the set's AV inputs. Obviously without knowing a lot more about Nicolas's requirements it is impossible for us to make specific any recommendations, but if he narrows his search to models made by the major players, namely Hitachi, JVC, Philips, Panasonic, Sony and Toshiba, and reads through the specifications he should find what he wants. Conversion is always a last resort as even the best 'consumer' digital standards converters produce some reduction in picture quality or picture artefacts.


Watching European satellite channels in the USA is a no-go; apart from channels that are actually re-broadcast there from local satellites. It's all down to 'footprints'; TV satellites are in a geostationary orbit 36,000km above the equator and aligned latitudinally with the countries or regions they serve. They orbit at the same rate as the Earth, so they appear to remain in a fixed position in the sky. In order to maximise their limited power outputs they generate a tightly focused beam, targeted at the specific areas where the services are to be received. This area of coverage is called the footprint and reception is almost impossible outside the area, even on the fringes you need a much larger dish.



Name David Cuss

Kit n/a

Problem David wants to build up a home cinema system, but his budget doesn’t quite stretch to specialist-store prices. He plans on buying online and through mail order, but has been put off by his specialist dealer who talked about ‘grey imports’ and how these are difficult to get repaired in the UK. Are cheap products all grey imports and is this really a big problem


Expert Reply

Let's begin by clearing up a few misconceptions about Grey Imports. It refers to any product – from trainers to cars -- that are not imported through normal channels, and distributed by a manufacturer's authorised dealer network. Grey imports are not illegal to sell or buy nor are they in any way inferior to their normally imported equivalents as they almost certainly came off the same production lines. The only technical problem with buying grey imports, at least as far as AV equipment and electrical goods are concerned, is differences in specification and power supplies. Generally speaking it's not a good idea to buy 'grey' video products (TVs, DVDs, camcorders, VCRs etc.), unless you know what you are doing as you could get lumbered with the wrong TV system, and avoid buying any mains-powered products made for the US or Japanese home market as they will probably have 110V power supplies. Products destined for Europe bearing the CE mark are usually okay to use in Britain but always check. As far as guarantees are concerned, if you buy a grey product in the UK and it goes wrong 'in a reasonable time' the retailer who sold it to you is bound by The Sales and Supply of Goods Act 1994 and Supply of Goods and Services Act 1982 to provide a refund or replacement. If you buy abroad, either personally or via the Internet you may well be on your own if it packs up. However, providing it's made by a company with a UK distribution network and the same or a very similar model is sold here you shouldn’t have any problems with spares or getting it fixed, though you will probably have to pay.



Name ‘Dok’

Kit n/a

Problem Dok is confused about Dolby Digital. Dok has heard about a system called ‘AC3’. How is this different from Dolby Digital 5.1?


Expert Reply

AC-3 and Dolby Digital are brand names and they are actually one and the same. AC-3 started out as an in-house term, coined by Dolby Laboratories in 1992. It refers to a third generation digital 'Audio Coding' system, developed for high quality digital surround sound in movie theatres. As a matter of interest AC-1 was introduced in 1985 and was used for satellite transmissions, AC-2 is a professional audio distribution system, developed in 1989. Dolby wisely decided that AC-3 sounded a bit too teccy for consumer consumption so the name was changed to the rather more glitzy Dolby Digital.


Dolby Digital is one of a number of multi-channel digital surround sound technologies known generically as '5.1' systems. The other well-known system, also used in consumer equipment, is dts or digital theatre system. Like Dolby Digital dts started life as a high quality surround sound for cinemas. In both cases the '5' refers to the number of discrete (i.e. separate) full bandwidth channels. These are used for right and left stereo, heard through speakers either side of the screen, a centre channel carrying dialogue and right and left stereo surround channels, heard through speakers to the side and behind the listening position. The '.1' channel has a narrow bandwidth and is carries low frequency bass sounds, and is mainly used for effects.


Dolby Digital, AC-3 and dts are not to be confused with Dolby Surround, which is an older analogue surround sound system.  In Dolby Surround four channels (right, left, centre and rear) can be encoded into a normal stereo soundtrack – these days it's mostly used on pre-recorded movies on VHS tape and some TV programmes. Dolby Stereo or Dolby 3 decoders extract just the front stereo and centre front channels; the fourth rear channel is extracted using a Dolby Pro-Logic decoder. 



Name Michael George

Kit Hitachi C36WF810N


Problem Michael is keen on buying a high-end DVD to match his built-in progressive scan-ready Hitachi set. He is confused about the different types of progressive scan around. Is the progressive scan system on DVD players better than the one fitted to his TV set? Do you have to use component video to get the benefits of progressive scan or will S-Video or RGB do? Finally, is it true that progressive scan is only possible on American DVDs?


Expert Reply

The technical explanation is a bit involved but the basic concept is reasonably simple. Normal TV pictures are made up of 625 lines, they're displayed in strict sequence, first the even numbered lines, then the odd ones, and the two 'fields' as they are called are meshed together or 'interlaced' on the screen to make one frame or still picture, which you see 50 times a second to create the illusion of movement. For the most part it works well with material originated on video but when movie film is transferred to the video medium the fluidity of movement suffers. That's due in part to the difference in frame rate of film and video (films are shown at 24 frames per second) and the interlace effect, which also exaggerates the line structure of the image. Progressive scan DVD players works by 'de-interlacing' the picture, so that instead of sending odd and even fields all 625 lines are read out in order and the picture is drawn in one go, as it were, and this also means the gaps between lines are smaller and the picture has a smoother, more movie-like quality. This trick is carried out by circuitry in the DVD player, on the digital data as it comes off the disc. Progressive scan is not a function of the disc, all DVD recordings are effectively interlaced, however some recordings may have 'flags' embedded in the data, which helps some PS players to decode the information.


A progressive scan video signal from a DVD player can only be shown on a progressive scan TV. The Hitachi C36WF810 is not a progressive scan TV in the absolute strictest sense understood by DVD aficionados since it works on the incoming analogue video signal and de-interlaces that moreover it lacks the necessary 'component' video inputs that allow it to work with a progressive scan DVD player. De-interlacing an analogue signal is quite a business since it involves several stages of analogue-to-digital and digital-to-analogue conversion, each of which introduces noise and processing artefacts, which some purists claim is not as good as the 'real thing'.




Ó R. Maybury 2001, 0607




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