AUDIOCLINIC (Feb. 1989)

Amplifier Buzz

Q. I have an integrated amp that worked well for quite some time, but now I hear a 60-Hz buzz in the loudspeakers. This noise is unaffected by the setting of the volume control. What needs to be done in order to eliminate this problem?

-Gary Kufchak, Downey, Cal.

A. I can think of a couple of reasons why your loudspeakers are producing a noise of the sort you have described.

Perhaps the amplifier is working fine but you added a light dimmer or some other household controller; some of these devices put tremendous spikes on the power line. These spikes force their way into the amp and can be heard as the "buzz" you described in your letter. I have not found a cure for this kind of interference, other than to remove its source-the dimmer or whatever.

Perhaps you have moved to a new location which is close to a TV broadcast station, or maybe one has begun operation near your home. This could cause TV signals to enter your amp, either via the power cord or as a result of the speaker leads acting as an antenna. If this is the case, ferrite beads placed either on the power cord or the speaker leads may help remove the noise.

It is also possible that the amplifier's power-supply diodes are becoming leaky or that the capacitors which are often shunted across the diodes-to prevent the very buzz you're experiencing-have broken down. If so, replace the diodes and their capacitors. (No, I don't mean the filter capacitors. I refer to those which are likely to be physically between each diode's cathode and anode.)

Psychoacoustic Perception With Hearing Loss

Q. I have a fairly severe hearing loss, mostly sensorineural, with a slight peak at 2 kHz and a 40-dB threshold drop at 4 kHz, plus another drop of 10 to 15 dB at 8 kHz. I do not yet have any quantization of what "recruitment" is doing to my loss at listening levels.

How can I get theoretical, physiological, and practical information on what this hearing loss means with regards to the psychoacoustic effect at high frequencies? What happens if I try to compensate by boosting highs?

-Ivan E. Cushing, Tyler, Tex.

A. Certainly some or all of the information you are interested in can be obtained from a good medical library.

It is apparent from the knowledge you already have that you have undergone extensive testing. You can probably get some of the answers you seek, and information on where to find the others, from the people who administered the tests.

I'm not at all sure this knowledge will do you much good. If you originally had "normal" hearing, you're in the best position to know how your present level of hearing compares to your previous level, even if the loss was gradual. If not, your request is similar to that of a blind person who asks for an evaluation of how his management of his affairs compares with that of someone who possesses sight.

I have a feeling, therefore, that you'd be well served by saying "Who cares?" rather than delving into something which, when understood, won't affect your hearing anyway. If that sounds cold, I don't mean it to. Believe it or not, I can put myself in your place, to some extent, because I am blind. I have not felt a need to learn all about what I don't have; I find it much better to concentrate on what I do have.

As to determining the effects of adjusting highs, try it. Use an equalizer, which "slices" the spectrum into small pieces, so you can try different portions within your various zones of high frequency loss. Try both boosting and cutting highs. Only you will know how much difference you perceive. As a backup, ask a friend who has some knowledge of sound what he perceives when you make the changes, then compare notes. With all of this, you still won't have a definitive answer.

There are many makes and models of loudspeakers, and they can sound vastly different, one to the next. Still, each brand has its adherents. If we all perceived sound in the same way, we would doubtless settle on one or two speakers as the ultimate choices.

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(Source: Audio magazine, Feb. 1989, JOSEPH GIOVANELLI)

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