Basic Audio is a free introductory textbook to the basics of audio physics and electronics. See the editorial for more information....

Questions and Problems

Author: N.H. Crowhurst

1. Audio transformers are used to produce step-up of voltage or current, to transform impedances to different values, or to make maximum use of available power (as in a loudspeaker). Comment on the relationship among these functions,

2. What are the basic differences between primary inductance and leakage inductance in a transformer?

3. Why is an air gap used in a transformer core? What determines the optimum size of the gap?

4. Can a flat-topped waveform at low frequencies be due to saturation? Comment on the relationship between frequency response, and the limitation imposed by saturation.

5. Would distortion due to saturation be more apparent in an amplifier using triodes or in one using pentodes? Why?

6. What features must be considered in the design of a good audio transformer?

7. Explain how a transformer can help performance (a) at the input to an amplifier, (b) at its output, (c) between tube stages, (d) between transistor stages.

8. What is harmonic distortion? Show how you would identify the presence of different harmonics on the waveform.

9. Explain two methods of measuring harmonic distortion. What would be considered an acceptable figure?

10. What is intermodulation distortion? Describe two different forms it can take.

11. Why are there inconsistencies among the results obtained in different distortion measurements?

12. Write what you would consider to be a good amplifier specification, and comment on the limited validity of any figures you may quote.

13. If a harmonic analysis of a waveform showed 1.6% second, 1.5% third, and 1.2% fifth harmonics, what would you expect the total distortion to be (assuming no higher harmonics are present in measurable quantity) ?

14. Comment on the significance of a harmonic measurement when the distortion mainly takes the form of clipping.

15. Comment on the use of square waves for testing (a) as to facts not brought to light that are revealed in other tests, and (b) as to forms of distortion that square-wave testing would not reveal.

16. Discuss some aspects of transient distortion that affect amplifier performance, which are not always included in the specification.

Last Update: 2010-11-03