Audioclinic (Dec. 1980)

Noise Build-Up in Records

Q. Please explain how "popping" and "crackling" noises get onto presumably clean phonograph records.

Can this situation be prevented? As an example, a new disc was free from noise the first time it was played. The third time it was played, however, there were many crackles and a few pops.

-Mark M. Fencke, Chicago, Ill

A. It may be that your stylus is worn or perhaps you are tracking too heavily, which would be especially serious with a low-compliance cartridge. Either of these situations will cause rapid record wear.

Care should be exercised when raising and lowering the tonearm in those cases where you are doing this manually. Searching for a given band can be harmful to the record if you slide the arm across the disc. This is particularly true for low-compliance cartridges.

Another possible cause for the gradual build-up of noise has to do with the environment in which the records are kept between playings. For example, if the records are played and then not returned to their sleeves and jackets, dust will accumulate on their surfaces. This dust will produce noise.

Along these same lines, phonograph records may pick up dust as a result of accumulation of dust particles on the turntable mat. This mat should be kept clean, so remember to leave the dust cover closed whenever the turntable is not in use. Additionally, every disc should be wiped with an appropriate brush both before and after playing.

Judging from the low number of playings before the crackles developed, however, it appears that static attraction of dust is a major problem for you, and I would recommend that you try one of the systems specifically designed to reduce static.

Impact in His Compact

Q. The stereo effect from my home system is not as dramatic as that produced by my automobile stereo sys tem. Why? Can I improve my home system's stereo impact?

-Lee Talbot, Livermore, Cal.

A. I believe that the automobile environment provides enhanced stereo separation because the individual speakers are at wide angles and tend to be beamed directly at the listener.

The sound from channel A does not have the space to merge with that of channel B, as is true in your living room.

Another aspect of automotive stereo sound is that many cars are fitted with speakers in both front and rear. Thus, you are really surrounded by sound.

For added impact with your home stereo system, there are a number of things you can try, which include dynamic range expanders and add-on tweeters. The first of these won't affect the stereo image, but this may be a large part of what you're experiencing.

I would also experiment with the placement of your home speakers, moving them further apart and per haps angling them away from each other. Since much of the directional information is in the upper midrange band of frequencies, you might try using an equalizer to lift this band gent ly. I suspect, too, that much of your reaction stems from an accurate perception of the car's smaller closed environment versus your home's larger, more open listening area.

Noise During Changer Cycling

Q. I have a fully automatic turn table. Whenever a record is over and the arm is about to pick itself up, there is a "pop" sound, even on brand-new records. What is the cause of this?-

Mark M. Fencke, Chicago, Ill.

A. It may be that the muting circuit, if you have one, never does short out the cartridge. Thus, the sound you hear is the stylus as it is lifted from the surface of the disc.

Perhaps this sound is that of a "click" on the disc itself. Very often there is a click at the point where the locked groove starts up from the run-

out groove. Run-out grooves can often be noisy, but this is not true of all discs.

To determine which of these two conditions is the real cause of your problem will require that you locate a disc which you know to be free of clicks in both the run-out and the locked grooves. To make sure you do have such a disc, play it on a manual turntable so you can be certain to hear the complete run-out and locked grooves.

Play this disc on your turntable several times and note if there is a distinct click present each time the tonearm is about to lift. If it turns out that there are clicks present only occasionally, this probably indicates an intermittent condition in which the muting switch sometimes closes and sometimes does not. If the noise is heard all the time, this probably means that the muting switch never closes. If the sound never occurs, then it must be that the whole problem is the result of noisy run-out and/or locked grooves.

To Align or Not to Align

Q. I have a question about capacitors. My tuner is a comparatively old one. If I replace the capacitors in my tuner, will the tuner require realignment?

-Darrel Babin, APO N.Y.

A. If you replace all of the capacitors in your tuner, including r.f. bypass and coupling capacitors, and i.f. bypass and coupling capacitors, realignment will be required. However, unless something is obviously wrong with your tuner, I see no need to change the various capacitors.

I can see where, with age, you may find it necessary to replace some power supply electrolytics as well as electrolytic interstage-coupling capacitors, emitter or cathode bypass capacitors, etc. There is usually no need to change the disc ceramic and mica capacitors found in the r.f. and stereo decoder portions of the tuner.

Name That Tuner

Q. It is my understanding that digitally synthesized tuners always automatically tune to the exact center of a station's assigned frequency and thus eliminate drift and tuning problems.

However, is there such a thing as transmitter drift which could cause the center channel point to move away from its assigned (and tuner-synthesized) frequency, thereby foiling all listener attempts to achieve the best possible reception?

-Greg Jones, Ann Arbor, Mich.

A. Synthesized tuners tune to the true center of an FM channel, provided that the tuner is properly aligned and provided that this alignment is checked periodically for changes. The stations themselves will not drift off their assigned frequencies. Because there are strict government regulations concerning frequency stability of FM broadcast transmitters, this should not normally be a cause for concern.

(Audio magazine, Dec. 1980; Joseph Giovanelli )

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