|
[ Go to March 1997 Table of Contents ]
Features
-- by John Woram
We've come a long way from the days when the only peep out of our PCs was a beep. Today, multimedia is everywhere. And the PC version has much in common with its cinematic big brother-action video up front and Surround Sound everywhere else. We'll take a close look at the audio side of multimedia, and offer you some sound advice for getting the best results not only from what you've already got, but from what's currently available. There's probably no such thing as a CD-ROM drive that won't play audio compact discs, and the sound card is now almost as common as a hard drive controller. Although today we pretty much take the sound card's functions for granted, a quick summary of its features and interfaces to the outside world may be worthwhile if you're in the market for a new one. If you are, make sure the card has what you need-not all cards have all the features listed here (see sidebar below) Sound Blaster compatibility. Many game programs are written to run on a system whose sound card supports Sound Blaster compatibility mode settings of DMA 1, IRQ 5 and I/O port 220. Most low- to midrange sound cards offer this compatibility mode, but high-end cards may not. If you're a dedicated gamester, or you use other multimedia software that requires Sound Blaster compatibility, make sure your sound card offers it. Output jacks. In a good home music sound system, you'd expect to find an amplifier as big as-and often heavier than-a PC system unit. So how does a quality audio amplifier squeeze its way into a tiny chip on a sound card? It doesn't. The sound card's on-board amplifier may deliver a few watts to the rear-panel speaker jack, which is sufficient to drive a pair of otherwise-unpowered speakers at a moderate level for noncritical listening. The signal-to-noise ratio is usually poor, and for good reason. The inside of a PC cabinet is a hostile environment for audio. With all those clock frequencies whizzing by, the little amplifier has a tough time separating signal from noise. All things considered, it does a decent job of it, but for better sound, use the unamplified line-out jack to feed external amplifiers-either in a separate unit or built into the speakers. Input jacks. When you play a music CD, its digital bit stream is converted to analog audio within the CD-ROM drive's own on-board electronics, then routed via separate cable to the sound card. On an internal drive, the cable goes to a multipin connector on the sound card, and the CD audio fader on the on-screen mixer controls signal level. An external drive has a pair of rear-panel RCA phono jacks, which may be routed to an external amplifier or to the line-in jack on the sound card, in which case the line-in fader controls signal level. If you need the line-in jack for CD audio and also have some other external audio device, look for a sound card with both a line-in and an aux-in jack. The latter is just another line-in jack. Better yet, get an external mixer. (I'll discuss this later.) If you have a microphone-input jack, use it only for a microphone, because its internal amplifier is designed to handle such low-level signals. Any other signal fed into this jack will be severely distorted. If your sound card's mike jack supports an electret condenser microphone but you don't use it, stick a piece of tape over this jack so you don't plug something into it by accident. Such sound cards deliver 5 volts DC to the microphone, which is good (see Optimizing Windows, February, for a few more details). But the sound card will gladly send the same 5V to the right side of a pair of headphones plugged into the same jack, which is not so good. Chances are the headphones-or anything else accidentally plugged in here-won't be damaged, but why take chances? I/O connector. Most sound cards also provide a multipin D connector, which may not be labeled on the rear panel. If all else fails, count the pins. If there are nine, it's MIDI only; 15 make it a combination joystick/MIDI connector. In either case, the interface cable should lead to two round 5-pin male MIDI connectors, labeled "in" and "out" (or color coded), and used to connect to an external synthesizer. The same cable may also lead to a 15-pin plug for a joystick. SCSI or IDE CD-ROM interface. If you got your CD-ROM drive and sound card as a package deal, the sound card should have the appropriate connector on it for the drive's data cable. But if you bought the sound card separately and need an interface to your CD-ROM drive, make sure the card has the right connector. This may not be an issue if you have an existing SCSI card that will support your SCSI CD-ROM drive, but if you were depending on the sound card for a CD-ROM interface and discover too late that one is IDE and the other SCSI, you're not going to be happy. Who's in Control Here? As you become more familiar with your sound card's features, you may get less comfortable with one of them-its control system. As a playback-only device, the on-screen mixer is more than adequate to adjust the levels of various sound sources, and it's okay for recording, too, provided you can make do with a simple set-it-and-forget-it adjustment. But for anything beyond that, you should seriously consider an external mixer. (Again, see Optimizing Windows, February.) When you're out shopping, make sure you find a mixer with slide faders. A rotary-knob device saves space and a few bucks but makes it difficult to adjust more than one signal at a time. And, to do a decent fade-in, fade-out or cross-fade between two sources, slide-fader control is a must-unless you're short on cash, and have lots of time and a third hand. When you unpack your mixer, just feed its stereo output into your sound card's line-in jack and set the on-screen line-in and master faders to about 75 percent maximum. Then connect all your sound sources to the mixer. Within reason, you can control PC sources ordinarily handled by the on-screen mixer, such as the playback of MIDI files and audio CDs. If you have an external synthesizer-keyboard or otherwise-you can feed a MIDI file out to it by hooking the sound card's MIDI out connector to the synthesizer's MIDI in. Then route the synthesizer's headphone or line-level outputs (not the MIDI through port) to the external mixer. For CD audio, run a cable from the CD-ROM drive's headphone jack to a stereo input on the mixer. If there is no stereo input on the mixer, use two mono inputs instead. If the drive is external, use the RCA connectors on the back if that's more convenient. If the CD-ROM drive's front-panel controls are inoperative, it's probably because Windows 95 has taken over control of the system, as it would if you used the CD Player applet during the current session. If auto insert notification is enabled and you insert an audio disc into the drive, CD Player automatically launches and the front-panel controls remain disabled even after you close the player applet. To get around this, eject the disc, then hold down the Shift key and reinsert the disc. This prevents Windows 95 from grabbing control, and the front-panel buttons should now function properly. Sometimes pressing the Play button twice is all it takes, but check your drive documentation for specific details. Watch Out for the Phantom You can connect microphones directly to the mixer, but you won't be able to use the typical sound card electret microphone, because it depends on the sound card for its supply voltage. Professional-grade nonelectret condenser microphones require an external power source for the microphone's built-in electronics. Some accept a battery, but many modern mixers contain a built-in phantom power supply to send a DC voltage out to each microphone, whether it needs it or not. To prevent damage to microphones that don't support phantom powering, the voltage is routed to both balanced lines in the microphone cable, where a pair of matched resistors in the microphone housing deliver it to the electronics. A noncondenser microphone won't have these resistors (or the accompanying electronics) and, because there's no difference in potential on the two signal lines, it's as if the phantom power weren't there at all-hence the name. Phantom powering is generally quite safe, but you should take a few precautions. If you don't have any microphones that want it, just turn the phantom power off and forget about it. You'll find a separate switch somewhere on the mixer. If you do need phantom powering for some microphones, make sure you don't plug an unbalanced microphone into a powered microphone input on the mixer because an unbalanced microphone can be damaged by the voltage. Also, turn the power off while plugging and unplugging microphones, especially older (and priceless) ribbon microphones. If you're not sure about all this, turn the phantom power off until your local mike freak gives you the okay. Speaking of Speakers Your next concern is getting the right set of speakers. If space is tight and you wanted a new monitor anyway, you may want to look at-and listen to-one with built-in speakers on either side of the display area. Avoid this if you can, however-although there are probably worse locations for speakers, none come immediately to mind. A fair amount of creative engineering went into the peaceful coexistence of audio and video monitors within (almost) the same space. Some multimedia monitors even have a built-in microphone somewhere on the front panel-an ideal location for videoconferencing. You're better off using something else for your important audio productions, because even though sound quality will meet the demands of voice communication, Web noises and the Windows 95 arsenal of WAV-file sound effects, you shouldn't expect an awesome audio experience. And remember, if you replace the monitor later on, you'll need replacement speakers and a microphone, too. If space allows, you can always run the sound card's line output to your home audio system. Even better, get a pair of small- to medium-sized speakers to place on either side of-and slightly removed from-the video monitor. Get Wired When you're connecting all this external gear, it's easy to get tangled in the cabling, especially if a mixer is involved. Beyond taking the time to make sure the outputs go to the inputs, and vice versa, keep the following points in mind: Tip-ring-sleeve plugs. The plug, which looks like a conventional stereo headphone plug, has three components: tip ring and sleeve. The order of the signal they connect to is left audio channel, right audio channel, ground. Red is right. With apologies to Lenin's ghost, any connector colored red designates a right-channel signal line. The left channel is typically white or black, or, for that matter, any color other than red. Be adaptable. If the plug on the cable doesn't match the jack on the hardware, don't worry. Radio Shack and most musical-instrument stores will have a wall display covered with adapters. Save yourself a lot of grief and buy what you need-home-brew adapters have a way of miswiring themselves. CD audio. Remember that the audio output from a CD-ROM drive always gets to the sound card via a separate cable. That is, it never travels down the flat cable that handles everything else. Name that tone. If you need to check microphone lines and don't have an assistant, consider a tone generator. The battery-powered Shure model A15TG ($86) plugs into a mike line and produces a constant 700Hz sine wave, which is a great help in keeping a mike line active while you figure out why it isn't working. Hum a few bars. Listen to your speakers. If they're AC-powered and you hear them humming in the background, relocate the power cable to a different wall socket. If possible, plug it into the same circuit that powers the PC. Don't use a ground-lift adapter unless you need to insert a three-pronged plug into an old wall socket. If the hum persists, disconnect audio cables one at a time until you find the culprit. You should be able to eliminate the hum with routine test procedures, but if all else fails, you may need to investigate the house AC service or get some audio cables with the shields connected at one end only. Don't test your eardrums. Don't wear headphones while experimenting. An accidental signal blast can do a lot of damage which, if you're very lucky, won't be permanent. Put It All Together The sonic side of your multimedia PC need not be a budget buster, especially if you don't expect to get into serious production work. Decide which of the following categories best describes your needs and then choose your hardware accordingly. Entry level. Even if you think multimedia doesn't deserve space in your computer, you still may need some basic sound capabilities to support videoconferencing, pronouncing dictionaries and other strictly business applications. If so, MIDI is probably not an issue, so you can save a few bucks with a sound card that offers nothing more than FM synthesis capabilities. Forget about microphones and irrelevant sound card features and get a pair of small, inexpensive speakers. Battery power is okay, but if the speakers don't go anywhere, you may as well plug them into the wall and forget about changing batteries. Intermediate. If you're an audiophile in training, the microphone that comes with the sound card should be more than adequate. The sound card should support wavetable audio and a joystick port, if you need one. The same port will probably support MIDI in/out facilities, even if you don't need them. But if you do, make sure they're in there. Then figure about $100 for a nice pair of self-powered speakers. Windows 95's own sound-support software, plus whatever comes with the sound card, should meet most if not all of your needs. Advanced. If you're serious about sound, get a professional-grade microphone whose polar response suits your specific needs. (See sidebar, "Testing, 1, 2, 3 ....") Serious multimedia production work demands a serious external mixer, such as the Mackie 1402-VLZ Mic/Line mixer ($599). With a good mixer on the table, you won't need a microphone input jack on the sound card. If you can find one with two stereo line inputs instead, so much the better. Otherwise, get a line-matching transformer if you want to use the unneeded mike input as a second line-level input for a mono source. Make sure the sound card has a MIDI port for an external synthesizer, and check out one of the high-end speaker systems mentioned in the sidebar "The Skinny on Speakers." Now all you need is a good pair of ears. Senior Contributing Editor John Woram is the author of The Windows 95 Registry: A Survival Guide for Users (MIS: Press, 1996). Contact John in the "Optimizing Windows" topic of the WINDOWS Magazine areas on America Online and CompuServe, or care of the editor at the e-mail addresses here. Copyright (c) 1997 CMP Media Inc.
|