J. Gordon Holt

To "Test Your Hi-FiQ" Score 5 points for each correct answer, then subtract 5 points for each incorrect answer. A score of 100 or better means you're an audio genius, 80 is very good, 60 is just fair. If you scored less than 30, you'd better brush up on your audiana.

1. (a) The smaller radii, in contact with the groove walls, provide better tracing of closely-spaced groove modulations.

2. (b) When the stereo difference signal is not received, both stereo channels are combined and heard together as a mono signal.

3. (a) Watts are watts, whether they are AC, DC, or British.

4. (b) It is the mass of the radiating surface that determines its treble performance. Size actually has nothing to do with it, except that it just so happens that most large radiators are heavy. A large radiating surface can, however, be light enough to be an efficient treble reproducer, as in electrostatic speakers and the corona-discharge speaker (which uses air alone as the radiating surface).

5. (c) If it's used at all (and many listeners prefer not to), loudness compensation should be used when reproducing any sound less loudly than it would have been heard originally.

6. (b) Force is the total amount of energy applied to the groove as a result of tracking weight. Pressure is the amount of this force that is applied to each unit of contact area. Thus, while the tracking force might be only 3 grams, the very small contact areas betwen the stylus and the groove walls may produce pressures on an order of several tons per square inch.

7. Both (a) and (c) are correct. If you checked both of these, give yourself an additional 20 points. It is normally impossible to play any 4-track tape backwards, because reversing the direction of the tape simply serves to reproduce the other two remaining tracks, forwards.

8. (b) There's no inductive winding in your hand to radiate AC into the pickup's coils. Hand-induced hum is capacitive, and is picked up by any unshielded signal-bearing part of the pickup, such as its output leads.

9. (b) The input load resistor serves to damp out the high-frequency resonant peak that might normally occur between the inductance of the pickup's coils and the capacitance of the average tonearm's shielded output cables.

10. (b) Selectivity is the ability to separate stations that are close to one another in frequency. The ability to receive only the stronger of two stations of the same frequency is called capture ratio.

11. (c) The same electrostatic force that attracts dust to a disc and makes Saran Wrap adhere to a refrigerator dish is also used to vibrate the radiating panels of electrostatic loudspeakers.

12. (a) Slightly heavy is better than slightly light, because the battering forces of a stylus rattling around in the groove are more destructive than those imposed uniformly on a groove by somewhat too high a force.

13. (b) The vertically-mounted ribbon is generally open at front and back, so pickup occurs from these directions. Sounds coming from the sides don't move the ribbon, so the pickup pattern will be shaped like a figure 8.

14. (b) The signal source and the measurements are the same. Only the test conditions differ.

15. (b) The friction due to viscous damping diminishes as the arm moves more slowly; pivot friction is likely to be greatest at slow motional speeds.

16. (c) The largest pipe organs (ones in Convention Hall, Atlantic City, NJ, and in Wanamaker's Department Store, Philadelphia, for instance) have a 64' diapaison stop that put out a viscera-shaking 16Hz. It rattles windows and feels like an earthquake but it is not readily audible. The lowest frequencies ever encountered on most stereo discs is in the vicinity of a modest 36Hz.

17. (b) Tracking distortion is due to a stylus's inability to maintain contact with both groove walls. Tracing distortion is failure of the rounded playback stylus to follow the exact original path of the triangular record ing stylus, even though there may be no loss of contact with either groove wall. Tracing distortion is measurable, but since the conditions that lead to it will usually also cause tracking distortion, which is much more audible, the tracing distortion is rarely audible at all.

18. (e) The amount of amplifier power needed to make a certain amount of noise in a given room is entirely a function of the loudspeaker's sensitivity. The greater the sensitivity, the less power is needed.

19. (d) Although cymbals can put out considerable energy at high frequencies, they are generally recorded in a large auditorium where they may be conveniently located at the rear of the orchestra, well away from the mikes. The xylophone is usually the worst trouble-maker because, under its typical closer-miking conditions, the initial strike transients from the wooden mallets present the microphones with impulses far stronger than those picked up from cymbals.

20. (b) Out-of-phase loudspeakers will have thin bass and poor center-fill, but they will not be noticeably affected by the setting of the preamp's function switch. If the pickup is out of phase, however, channel blending will tend to cancel all signal that is common to both channels, and in the case of a mono disc this comprises everything recorded thereon.

21. (c) A nuvistor is a vacuum tube whose electrical characteristics make it ideal for use in RF circuits, such as tuner input stages.

22. (b) Most high-frequency tracking problems are due to excessive moving mass in the stylus rather than to inadequate compliance. Compliance is most related to bass and middle-range trackability.

23. (c) A lightning discharge produces an impulse of energy, which is an amplitude modulation. Its energy actually spans an extremely wide range of frequencies, but the intensity at any one frequency is relatively small, and it does not act to shift frequency of the transmission that's being received by the tuner. So, the frequency-shift-sensitive tuner doesn't respond to it. It is only when the tuner is off-station, or is receiving a relatively weak station, that its gating system is open to and susceptible to AM interference.

24. (b) If the arm is statically balanced in all directions by a counterweight and the tracking force is applied by a spring system, levelling is not critical. With arms that apply their tracking force through a slight unbalance of the counterweight, a slight tilt of the phono unit can make up for lack of built-in bias compensation.

25. (a) At 70° Fahrenheit, the speed of sound through air is 1130 feet per second. In order for 1130 sound waves to pass a given point in a second, each wave must be 1 foot long.