August 1, 2005

Thank you for your advice on preventing damage to my audio gear. Q: Do you have other advice you can offer?

Tony B.

A: Sudden changes in level from source to source are not only irritating; they can also cause damage by overstressing the delicate wiring in high-frequency drive-units.

By and large, most of the devices you hook together operate at "line level" and so are reasonably compatible, but this is not a real standard, and there can sometimes be substantial level differences from one source component to the next. In such cases, switching from one to another might well cause a fairly extreme jump in level (if it’s a drop instead, it’ll be a jump the next time you go in the opposite direction).

Unless your preamplifier section has individual input-level controls -- a rare breed indeed -- you have only a few options. The best is to buy source components that don’t exhibit these changes, which might well mean that you have to do a few exchanges before you get it right. Some of your components might have a choice of fixed or variable output levels, in which case you can match things up at the source. Or you might choose to insert your own trim pots prior to the preamp inputs, although that risks audible degradation.

Perhaps the only sure way to overcome such problems is to get into the habit of turning down the level before switching inputs; that can sound a lot smoother too.

Don’t jack it around. We all need to disconnect and reconnect components now and then, and if we’re in a hurry, it’s tempting just to move the cables around while everything is on. Sometimes that’s not a problem, but more often you risk a possibly damaging blast of hum as you make the reconnection. When you insert the "hot" lead of the first channel you connect, it usually makes contact with its internal counterpart before the grounded sleeve on the cable engages the sleeve of the panel-mounted jack. For that moment, you have an ungrounded connection that can create a very loud 60Hz noise; it’s much worse if the connection is to a power amplifier, because it may well use the amp’s full output, if even for a split second. The only way to avoid this is to make sure the system is shut down when you make or break any connections.

Don’t zap your tapes. Audio and videotapes are recorded by applying a varying magnetic flux to their oxide surfaces, and they are erased the same way. Sometimes it’s possible to erase them inadvertently -- not by hitting the Record button by mistake, but by storing the tapes too close to magnetic objects. Permanent-magnet door closers are a common culprit, as are the fields generated by television sets and unshielded speakers. Rarely is a tape completely erased; the effect is gradual and cumulative. By the time you notice that something’s missing -- usually the high frequencies -- it’s too late. Keep such magnetic ambushers at least a couple of feet away from your tapes.

Don’t squish the plastic. Given its tiny size and extremely slow record/playback speed, it’s a wonder the audio cassette works at all. The miniaturization that it represents means that only very small problems can cause major audible headaches. Many of these can be averted by careful storage of your tapes when they’re not being used, especially if they may be on the shelf for a long time -- years, perhaps -- before you listen to them again.

Keeping audio cassettes away from extremes of temperature and humidity and from stray magnetic fields is a good precaution. They should also always be kept in their plastic boxes, to keep dust and other airborne contaminants away from the tape and guides. It’s also a good idea to make sure the tape is wound smoothly before you store a cassette; an uneven wind can cause permanent deformation, which might disturb the tape-to-head contact when you play the tape in future years. The best way to ensure a smooth wind is to flip the cassette to its B side, rewind to the beginning, and then play the tape through at normal speed. This will prevent some layers of tape from having edges that protrude and can be bent.

Don’t scratch your discs. Compact discs are pretty hardy, but they’re not invulnerable. Still, some elementary care should help them last almost indefinitely. First, always keep them in their jewel boxes (or in the player, if you have a changer), to protect them from dust and grime. They should be stored vertically (though this is less critical than with LPs), and always handled by the edges.

If you see a buildup of dirt on a CD, you can clean it with a proprietary cleaner or just a clean, soft cloth. Always wipe directly across the disc, from center hole to edge -- never with a circular motion. If by chance you wipe a bit of grit into the surface, the player will ignore the scratch if it goes across the datastream; but if it is parallel to the data, it can be much more disruptive.

Remember, too, that it’s the label side of a CD that is most fragile, so handle it with care: never write on it with a marker (except one designed for the purpose) or place a sticker on that side -- both can dissolve the lacquer coating and let air in to oxidize the aluminum surface. If you find that the playing surfaces of your CDs are developing a consistent pattern of tiny scratches, it might be worth investigating whether or not your player has some tiny projection that is damaging the surface. Or it may simply be worthwhile to review how you handle discs -- it’s extremely easy to scratch the surface by brushing it over the spring-loaded grabber in a jewel box, for instance.

Don’t crank it across. It’s possible to produce some truly hideous -- and possibly damaging -- noises by not taking care with your FM tuner. Chances are that if you only listen to one station you won’t have a problem, but few of us are that exclusive. With older tuners or receivers -- the sort with a big tuning knob on the front panel -- the easiest way to change stations is to just give the knob a spin. But if the tuner doesn’t have an FM muting function, or if this feature is switched out, the high-level gobbledygook the tuner picks up between the station you’re leaving and the one you’re tuning in might well cause considerable damage, especially to your tweeters. Even if it doesn’t, it’s likely to annoy anyone else within earshot. The safest bet is to keep the FM muting on and turn the overall levels down until you have the new station tuned in properly. And curb the impulse to spin that knob.

...Ian G. Masters