PC audio - Now hear this

Sound is now as much a part of a PC as the mouse or keyboard but it wasn't always so. The original PC design made no provision for audio beyond a speaker the size of a 10p piece that could go 'beep' and, to be honest, that was more than enough for the applications that needed it.

What the PC design did include, however, was the capacity for expansion and it didn't take long for enterprising hardware manufacturers to come up with an expansion card that could create all manner of weird and wonderful noises. The sound card was born.

Technology has improved dramatically since those early days and many modern sound cards have features usually found only in music studios.

The last 12 months have seen ISA sound cards all but disappear, replaced by PCI models and, thanks largely to the demands of games programmers, 3D sound is now more or less the norm, as are cards that can drive four speakers.

Another interesting development is technology that allows your PC's speakers to make a noise without even using a sound card, and we don't just mean by picking up your local taxi firm's broadcasts ...

So if you're into making your own music or just want to dip yourself deeper into a virtual world, there's a sound card to suit, but which is the best? This month we audition 10 of the latest PC audio systems.

What does a sound card do?

A PC is a device that works with electrical pulses that represent two numbers - 1 and 0. Sound is a waveform that travels through a medium (air, usually) before reaching our ears. The former is digital, the latter is analogue, so how does one produce the other?

It's all down to digital to analogue conversion and essentially, that's all a sound card does. All sound cards contain a DAC (Digital/Analogue Converter) chip and it's this that's responsible for converting the streams of 1s and 0s that represent waveforms into sound we can actually hear.

So where does that waveform come from?

FM synthesis

There are two possibilities. The first is to create a waveform from scratch by 'synthesising' it and sound cards do this using FM synthesis.

FM (Frequency Modulation) synthesis mixes two sine waves (a carrier and a modulator) to produce a complex sound waveform. By varying the carrier and modulator waves, a close analogue of the waveform of virtually any sound can be produced. Unfortunately, while FM synthesis is great for such 'noises' as gunshots and explosions, it's hopeless at reproducing the natural sound of most musical instruments.

Wavetable synthesis

A better way to produce waveforms is to use a technique called wavetable synthesis (hence wavetable sound cards). Wavetable synthesis doesn't 'create' sounds at all but merely plays back and manipulates recordings of them.

The recordings are called 'samples' and anything that makes a noise can be recorded and played back by a sound card.

A sound card's wavetable performance hinges on the quality of the samples it's supplied with. Sample quality varies from excellent (the Guillemot ISIS) to appalling (all the digital speakers, of which more later) but, thankfully, all sound cards can use different sample sets to improve their performance.

Sample quality also depends on the original instrument recorded and the quality of the recording itself. All modern sound cards can make 16-bit samples at 48kHz, which is slightly higher than the recording quality of an audio CD. But the higher the sample quality, the more memory needed to store it, so all cards except the ISIS have done away with on-board memory and use main PC RAM instead.

The third way

Recent developments have resulted in yet another method of producing sound from a PC and, interestingly, it doesn't involve a sound card.

Digital speakers take advantage of the power of modern PC processors and the high-speed digital connections offered by USB - digital speakers plug directly into a USB port, bypassing the sound card completely.

The speakers still need a driver, just like a sound card but sound is actually generated using software built into Windows 98. The resulting waveforms are still in digital form by the time they leave the PC (via the USB lead) and the speakers themselves perform the necessary digital to analogue conversion.

Labtec, Microsoft, Philips and Roland offer digital speakers and these all work in the same way. The claimed advantage of digital speakers is better sound - the inside of a PC is electromagnetic chaos and this wreaks havoc with a sound card's ability to turn digital data into noise-free analogue information. But with digital speakers, audio data is still in digital form by the time it leaves the PC via the USB lead. Digital data is far less susceptible to electromagnetic interference and, better still, the data is only converted into an analogue form when it reaches the speakers - which are well away from any source of interference.

There are three points to bear in mind with digital speakers, though.

First, to play audio CDs on your PC, your CD-ROM drive needs to support digital audio extraction and only recent models do. Second, digital speakers place greater demands on a PC's processor than an ordinary sound card.

So if you use a low-end PC for playing games, you might have to do some settings tweaking to help with performance. The final point is also important for gamers - digital speakers don't provide a joystick port (unlike a sound card), which means you'll need some kind of USB controller.

Standards

All sound cards adhere to certain standards and this ensures a certain amount of compatibility with software. Essentially, programmers write code that assumes that a sound card - in this case - understands a set of common instructions. This means they don't have to worry about tweaking their software to work with every type of available sound card.

The biggest common standard used to be Sound Blaster and most cards are still Sound Blaster compatible. These days though, it's only really an issue if you want to play the ever-diminishing number of MS-DOS games.

Far more important is Microsoft DirectSound compatibility, since this determines whether a card will work with Windows. All the cards and speakers here support DirectSound and its 3D variant, DirectSound 3D.

DirectSound 3D creates 3D audio through two or four speakers. With two speakers, the 3D audio is 'pseudo-3D' and, to be honest, it's not much good. Aureal A3D Version 2 - as supported by the Diamond Monster Sound MX300 and VideoLogic SonicVortex 2 - is much better and if you're into games (the only software that uses it), you'll love it.

Environmental Audio - the standard used by the Sound Blaster Live! - isn't so impressive with two speakers but plug in another pair and you get an incredibly immersing audio experience with compatible games. Alas, the Yamaha WF192XG's Sensaura and the Guillemot ISIS's A3D Version 1 3D audio is pretty awful.

GM and GS standards are MIDI standards that are only of interest if you plan to create MIDI compositions. Suffice to say that a GM or GS MIDI file played on one compatible card should (samples permitting) play back the same on another. Yamaha's XG standard takes things a stage further for even more expressive MIDI but again, unless you're a muso, you won't miss it.

Sample quality

Wavetable sound cards all come with sets of samples for MIDI playback - one for almost every imaginable musical instrument plus a handful of special effects. With a good set of samples, you can barely tell you're listening to a sound card playing a piece of music and, in fact, some professional musicians make recordings using them.

Top of the sample list is the Guillemot ISIS, simply because its set is superb. The Yamaha WF192XG and Sound Blaster Live! are pretty close though, so a listen to all three might be useful if you're buying a card for composition purposes.

The rest of the sound card pack lag a way behind and their sample quality is merely average. Sadly, digital speakers rely on software wavetable synthesis and the samples provided with Windows 98 are of poor quality.

In other words, if you're into MIDI and you buy digital speakers, you'll need to invest in some better samples.

Memory

With the exception of the Guillemot ISIS (with 4Mb of expandable on-board RAM), all the sound cards under review here use the PC's RAM for storing samples. If you have lots of RAM, this gives plenty of flexibility with samples, since a set of high-quality ones take up lots of memory.

It's the same story with the digital speakers but you'll be pleased to hear that you don't have to use the Windows samples with them. You can buy other software wavetable synthesisers to replace Windows 98's own and Roland has a much better alternative in the shape of the VSC-88H Virtual SoundCanvas (£35).

Extras

There's quite a bit of other stuff in most sound card boxes, the most useful of which is a CD-ROM audio lead. You'll need one of these to play audio CDs on your PC through your sound card but only Creative Labs and Guillemot include one. The Sound Blaster Live! also comes with a separate blanking plate with a whole host of extra sockets, though these will appeal mostly to audiophiles.

All the sound cards also come bundled with software, usually a MIDI sequencer, some audio tools and assorted utilities. Don't be tempted by a card with a big bundle - you probably won't use most of the stuff if you're buying a card for general Windows use and games. Conversely, the digital speakers don't come with any software of note, so don't buy a pair if you're aiming to be the next Kraftwerk.

If you're after a good all-round sound card that will do justice to the latest games as well as cope with any musical aspirations you might have, then it's quite simple - buy the VideoLogic SonicVortex 2. Though essentially the same card as the Diamond MonsterSound MX300, it has the edge in terms of sound quality and has a better software bundle. It's also a touch more expensive but we feel that, overall, it's well worth the money, so the SonicVortex 2 gets the What PC? Best Buy award.

If you fancy saving yourself a fiver or so, then the Diamond MonsterSound MX300 is worth a listen but if you're feeling flush, the Sound Blaster Live! deserves serious consideration. For the money, you get a great-sounding card with enough tricks up its sleeve to keep everyone from gamers to musicians cackling with joy.

Installation

All the sound cards have a plug and play installation but some manufacturers make it easier than others. You can see from each card's ratings (in the table near the end of this article) which we thought the easiest, so we won't repeat that information here. We will mention the worst though - the Yamaha WF192XG. The card goes in easily enough but the driver installation has you install each component separately and manually, by navigating cryptic folders on the supplied CD-ROM. Shocking.

If your PC has audio built into the motherboard, this will need to be disabled before you fit a sound card, lest any hardware clashes arise.

The best way to do this is in the PC's BIOS but you can do it from Windows too. Just find the appropriate entry in Device Manager (right-click My Computer and choose Properties), right-click it, choose Properties and click the Disable button.

If you don't fancy pointing a screwdriver at your PC, stick with USB speakers. All you have to do with these is plug them into a free USB port - dead easy.

GLOSSARY

Analogue: Information that is continuously variable, such as a sound wave. Loud speakers produce analogue information.

DAC: Digital to analogue converter. A device that converts digital information to analogue form, and vice versa. Used by all sound cards.

Digital: Information represented as a sequence of numbers. PCs can only understand digital information represented by 1s and 0s.

FM synthesis: A digital synthesis system where complex sounds are created by modifying the frequency (Frequency Modulation) of two simple sound waves.

GM: General MIDI. A standard governing the set of sampled sounds used by all MIDI devices. A GM file created on one device will sound at least similar on another (the instrument samples may vary in quality but not in type).

GS: An extension to GM that offers more control over the way samples are played.

MIDI: Musical Instrument Digital Interface. A communications standard that allows musical information to be sent between digital electronic musical instruments. MIDI information can also be stored as a file and played back later.

Polyphony: The number of instruments or 'voices' that a sound card can play simultaneously. Usually 32 but 64 and 128 voices are not uncommon.

Samples: The digital recordings played by a wavetable sound card.

Any sound can be 'sampled' and played back at different pitches.

Sequencer: A program for creating MIDI compositions. The musical equivalent of a word processor.

SIMM: Single Inline Memory Module. Used by some sound cards to expand their on-board RAM.

Wavetable synthesis: A digital synthesis system that works by playing back digital recordings of actual sounds.

XG: An extension to GM developed by Yamaha that allows samples to be played with great expression.

CONNECTIONS

The part of a sound card that pokes out of the back of a PC has a number of sockets for connecting equipment. There are usually also connectors on the card itself. The most common connectors are:

1. Speakers - 3.5mm jack plug for connecting a pair of speakers.

2. Line in - 3.5mm jack for connecting an external stereo sound source for recording, such as a CD player.

3. Speakers 2/Line out - 3.5mm jack for a second pair of speakers for 3D positional sound or for an external recording device, such as a cassette deck.

4. Mic - 3.5mm jack for mono microphone input, useful for such software as voice recognition.

5. Joystick - works with any PC joystick and MIDI devices, though the D-shaped socket needs an adaptor for standard 5-pin DIN MIDI leads.

6. CD-ROM audio - links a CD-ROM drive (and other devices) to the sound card, so that audio CDs can be played through the speakers.

7. S/PDIF - allows a sound card to receive digital information direct from a source, such as a CD player, for very high-quality digital recordings.

8. SIMM slot - for expanding a card's on-board memory, no longer needed by most PCI sound cards.

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