An amplifier is the backbone of any audio system, providing the necessary power boost to turn line-level audio signals into thrilling highs, rich mid-range and booming bass. There’s a wealth of knowledge behind the construction and tuning of an audio amplifier, with a long and complicated history since the creation of the vacuum tube in the early 20th century.

1. John Bardeen and Walter Brattain, when working at Bell Telephone Laboratories realised that by making two point contacts very close to one another, they could make a three-terminal device — the first “point contact” transistor, which lead to the development of the audio amplifier in what year?:
a. 1944
b. 1946
c. 1947
d. 1948

2. In 1906, an American inventor and physicist, Lee De Forest, made the vacuum tube triode, which he called the: *
a. Audio Tube
b. Audio Triode
c. Audion
d. Electrical Audio Tube

3. When did transistor-based amplifiers start to become widely available and rise in popularity?: *
a. 1940s
b. 1950s
c. 1960s
d. 1970s

4. What is a ‘Class T’ amplifier?: *
a. An amplifier based on a Class D design
b. An amplifier with very low background noise levels
c. An amplifier with very high gain levels
d. All of the above

5. What are the four main parameters that influence the design of audio amplifiers?: *
a. Gain, equalisation, aesthetics and frequency response
b. Size, price, power efficiency and high distortion levels
c. Frequency response, background noise, gain and distortion
d. Heat levels, flat frequency response, weight and low background noise

6. What is the most efficient class of transistor-based amplifiers?: *
a. Class D
b. Class C
c. Class AB
d. Class C and D are equally efficient

7. What are the four main classes of transistor-based audio amplifiers?: *
a. Class 1, Class 2, Class 3, Class 4
b. Class A, Class B, Class C, Class D
c. Class A, Class B, Class AB, Class D
d. Class A, Class AA, Class AB, Class B

8. Bruno Putzeys is widely regarded as the leading designer of a type of audio amplifier known as Class D. While working at Philips Applied Technologies in Leuven, Belgium, Putzeys designed a compact, versatile class D amplifier module that he called the: *
a. PcD: Philips Class D
b. UcD: Universal Class D
c. AcD: Audio Class D
d. IcD: International Class D

9. What amplifier class is most commonly used in low-power applications (such as driving high-end headphones)?: *
a. Class A
b. Class C
c. Class AB
d. Class B

10. What year was the first transistor-based radio, the Regency TR-1, sold in stores?: *
a. 1950
b. 1951
c. 1953
d. 1954