AUDIOCLINIC (Q and A) (Aug. 1974)

Record Damage During Changer Cycling

Q. In your personal opinion, do you think records are damaged by using an automatic record changer of high quality instead of a manual turntable? I am thinking specifically of the short "sliding" that takes place when a record is first dropped onto another record-as well as the initial shock of the drop.

-Leonard Wiener, Chicago, Illinois

A. I do not think that the dropping of one disc onto another or the sliding of one disc onto the one below it during record changer cycling will damage your records in any way. If you examine the construction of modern phonograph records, you will note that the outer edge of the discs are thicker than the playing surface of the disc. Further, the center area around the label is also raised. This means that when two discs are stacked on each other, the two raised areas will make contact; the actual recorded area will not.

Of course, records can warp. When this happens, it is then possible for grooves to make contact. Even so, I have not noticed any signs of damage because of this. This is true even of lacquer discs, which are softer than vinyl pressings, and which do not have raised portions.

Equalizers and Warped Discs

Q. I wonder if you will help me with my problem. I use a Dual 1219 changer with a Shure V15-II cartridge. I also use an Acousta-Voicette equalizer and two Altec 1-7-500's. Since I connected the equalizer, each time I play a record, no matter how slightly warped it may be, I hear a low frequency flapping sound.

With the equalizer out of the circuit or with the low frequency filter of my receiver turned on, this sound disappears. Also, when changing records, the moment the stylus leaves the record, a low-frequency "thump" is heard. This sound is more apparent in one channel than in the other.

What can be at fault, the cartridge or the turntable?

- Val de La Guardia, Panama

A. The problem of "thumps" which occur each time the disc rotates or when the tonearm is lifted appears to have something to do with the equalizer.

When the equalizer is not in the circuit, you do not have the problem; when it is in the circuit, you do have it. I can only conclude, therefore, that the equalizer is producing some bass boost at low frequencies. Perhaps this boost occurs at frequencies which are too low to affect the sound of the program on the disc.

The fact that one channel produces more of this effect than does the other channel appears to be a problem of unequal response of the equalizers.

About the only way you can prove this is to make a frequency response run of each channel. You will probably see a bass rise on both channels, starting at perhaps 40 Hz. One channel, however, may show more of such a rise than does the other one.

The controls of an equalizer such as yours are sensitive. If you are just a bit off the true flat position of any control, you will experience a rise or fall in the response associated with that control.

Amplifier Overload

Q. I have a pair of relatively inefficient loudspeakers. My receiver is a 25 watt rms unit. Once in a while I wish to listen to my music at very high volume. When I do, the front panel lights on the receiver dim slightly, especially when low bass notes are struck. There is no exaggerated distortion until the receiver is driven to its full capabilities, but the dimming lights tend to make me think that I may be harming the amplifier.

Is this dimming a sign of amplifier overload? Am I harming my receiver by playing it this loud?

-Randy S. Parlee, Greenfield, Wisconsin

A. I suspect that, when you turn up the volume on your receiver to a point where the music is really loud, your power supply voltage falls below its normal level, thus dimming the front panel lights. This dimming is not necessarily an indicator of possible damage to the amplifier but it is obvious that you are running the equipment near its overload point.

Check your instruction manual to see if there is any mention of dimming lights as a possible warning device.

(Audio magazine, Aug. 1974, JOSEPH GIOVANELLI)

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