Audioclinic (Sept. 1983)

Speaker Cable

Q. Is there any advantage in using 16-gauge wire instead of 18-gauge wire when connecting a pair of speakers that will be located approximately 100 feet from the amplifier?

-Steve Hood, Independence, Iowa

A. Considering the run of 100 feet of cable between your amplifier and your speakers, there is definitely an advantage in using 16-gauge wire over 18 gauge line. In fact, losses are great enough because of this long cable run that even the 16-gauge wire is not large enough. I suggest that you use 14-gauge wire or even heavier.

Such a wire size is too cumbersome to allow fastening it directly to the speakers. You will need to splice in a short length of No. 18 or perhaps No. 16 wire in order to make the proper connections to the speaker. Another alternative is a special connector.

It may be that you are using a "wall box" from which your speaker cables will emerge. This is often the case. In that instance, the splicing can be done within the box, using wire nuts or per haps solder and electrical tape. Of course, the heavy-gauge wire could also be brought to a connector and its mating connector could be fitted to the lighter gauge wire. If you use this latter method, Do not use standard electrical plugs and outlets! This scheme is likely to result in the accidental application of 117 volts to the loudspeakers, with disastrous results! It is also a potential fire hazard.

Receiver Fading

Q. I own an AM/FM stereo receiver. When I play it at a low volume, the sound sometimes fades in and out or the sound shifts from one speaker to the other. What could be causing this?

-David Huffman, Terre Haute, Ind.

A. I can think of two causes for the problem you have described. First, there may be a defective electrolytic capacitor in one channel. This would account for the volume sometimes fading out, causing a shift of stereo balance over to the channel not affected by the problem. The receiver will play properly when run at higher volume because the added signal feeding into the defective capacitor shocks it into more or less normal operation.

The cure for a defective capacitor is to replace it-after doing some signal tracing to locate the bad one. The offending component might be a coupling capacitor or it might be an emitter-bypass capacitor.

The second cause for erratic volume might be a dirty or oxidized control. If most of the oxidation is at the lower end of the control, the contact between the element and the slider will not be solid, leading to volume changes.

In a similar manner, oxidation of contacts in tape monitor, selector and mode switches-as well as the balance control-all can produce annoying fluctuations in volume.

In any event, the cure is to spray the offender with suitable contact cleaner and immediately exercise the knob.

This will allow the cleaning agent to spread over the innards of the element and thereby do its job.

"Formed" Electrolytic Capacitors

Q. My Dynaco PAT-5 is so wired that, even when its power switch is off, there is a small amount of power still applied to the circuitry to keep the electrolytic capacitors "formed"-to prevent deterioration.

What would be the results in this connection if I left my power amplifier on all the time? I am concerned about keeping its electrolytic capacitors "formed".

-Charles E. Cump, Denver, Col.

A. If you use a piece of equipment regularly, there is no need to keep it turned on just to "form" its electrolytic capacitors. Deterioration of the dielectric will not be a problem except where the equipment is used infrequently.

Should this be the case, turn the equipment on at regular intervals, even though you may not wish to use it.

Piezo Tweeter Termination

Q. I replace' the tweeters in my system. The originals were rated at 20 watts at 6 ohms. The replacements are piezos. I was told that I should place a 6-ohm resistor across the terminals of each tweeter to be sure that the cross over network functions properly. The tweeters sound good as they stand, without the resistors. Is my setup all right or should I use the resistors?

-Thomas J. Rose, Bradley Beach, N.J.

A. What you were told about the need for connecting a resistor across the terminals of each tweeter was correct. With this resistor in place, the crossover network will produce the proper crossover frequency. There fore, you are likely to notice an improvement in sound with the resistors installed over what you are hearing now. Without the resistors, the tweeters will be fed by frequencies which are lower than those intended to be reproduced by the tweeters. This will produce an overlap between the tweeters and midrange units, which may create audible peaks in the frequency response.

Tape Out and Preamplifier Out

Q. Is "Tape Out" or "Rec Out" on a receiver the same as "Preamplifier Out"?

-Roger Ross, Peshastin, Wash.

A. "Tape Out" and "Rec Out" are not the same as "Preamplifier Out." "Tape Out" is extracted ahead of all volume and tone controls, whereas "Preamplifier Out" is taken from a later point in the circuit in order to include these functions.

(adapted from Audio magazine, Sept. 1983; JOSEPH GIOVANELLI)

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