Chapter 6-Integrated Amplifiers



As mentioned earlier in the first chapter, an integrated amplifier is a preamplifier and power amplifier in one single unit. The signal that is fed to it is amplified by a minuscule amount by its internal preamplifier section then amplified again by the power amplifier section to reach audibility.

To enhance the enjoyment of entertainment and facilitate the "home theater" experience, many of today's integrated amps. including some low priced units, include some form of surround sound circuitry. The term "surround sound" is often used very loosely. Identical sounds coming from the front and rear of a listener can be described as surround sound. The same thing with slightly delayed rear sound reproduction also qualifies. Such surround sound can be used with music or any other sources but the forms of home surround sound reproduction that are specifically designed for specially processed movie soundtracks include Dolby Surround, Dolby Pro Logic Surround, Lucasfilm THX Home Theater, and Dolby Digital (formerly known as Dolby AC-3). But more on these systems later under Surround Sound.

Among the common features found on an integrated amplifier are tone controls, a loudness switch, a moving coil input switch, mute switch, balance control, and speaker selection switch. A rare feature found on an integrated amplifier is a pair of d-a converters.

Tone controls alter the frequency response (see frequency response) of the sound. There are usually two or three controls: one for bass, one for treble, and the other for midrange. The bass control only alters low frequencies. For example, turning down the bass control would de-emphasize the sound of bass guitars and bass pedals while turning it up would make it louder. The treble control only affects high frequencies. So turning up a treble control would increase the music's clarity. Cymbal clashes, for example, would sound more vibrant. The midrange control makes sounds in the middle of the audible frequency range softer or louder. Most of the vocal range of sound lies in this range so this control could make singers sound more or less distant, depending on the setting.

Loudness switches or controls are similar to tone controls because they also alter certain sounds. Their purpose is slightly different, however. When we listen to music at low levels bass and treble sounds seem to lose their impact. With a loudness switch or loudness control these sounds can be emphasized to restore the lost impact.

One of the flaws we sometimes hear with some recordings is hiss; it's the continuous "sssssss" sound that comes from primitive or mediocre recordings and noisy radio broadcasts. With a high filter, this hiss noise is reduced to make your music sound more listenable. Switching in this filter, on the other hand, compromises the clarity of the sound, particularly the highs (high frequencies). As a general rule of thumb, remember that there's no such thing as a free lunch.

For those listeners who still have LP's a low filter or subsonic filter might be useful. As a result of heat or physical mishandling, some records may become warped. When they're played the warped portions are reproduced as low tones that are so low they're inaudible. These bass tones can actually damage the speakers if they're loud enough. Therefore, it's a good idea to use a low filter to remove these frequencies.

A source selection switch allows the listener to choose a tuner, turntable (phono), cd player, tape deck, or other audio signal as a listening source. But the setting of this switch can be overridden by a tape monitor.

With a tape monitor, you can listen to the sound from a tape deck regardless of the position of the source selection switch. Also, a tape deck hooked up to the tape monitor can record from any other component. On the other hand, the tape deck option on th source selection switch can record from all other components except the tape deck connected to the tape monitor. Some integrated amps have two tape monitors, which means that one tape deck can be connected to each monitor and both tape decks can record from any source chosen on the source selection switch.