How Stereo Receivers Work

Curious about how stereo receivers work? Radios have come a long way since their inception, and today’s stereo receivers combine the function of a radio plus an amplifier and switching source for other audio components, such as tape decks, CD players and televisions.

Consider a stereo receiver as the hub of an audio system. A stereo receiver contains an AM/FM radio and an amplifier. Jacks on the back of the receiver give access to the input of the amplifier section. Switches on the front of the unit route inputs from outside sources to the amplifier section. The radio is wired to a switch internally within the receiver, but external audio devices must be connected to the jacks on the back. Once connected, it is a simple matter of turning a selector dial or switch to choose the desired audio source.

Investigating the features of stereo receivers, you’ll find that at a minimum most receivers will have input jacks for a CD player, a tape deck and an auxiliary input. These inputs are designed to accept audio signals from these devices and other similar components whose signal level is said to be at a "line level." Line level signals are not strong enough to produce sound from speakers, and so must use the stereo receiver’s amplifier section. The output of the amplifier is designed to connect to a pair of speakers positioned to the left and right of the listening area. Connections for speakers are typically made by either inserting speaker wires into push-type connectors or with screw terminals.

Playing records on a turntable also requires amplification, but audio coming from a turntable is weaker than line level signals. A turntable signal also requires special equalization before being sent to the main amplifier. For this reason, many stereo receivers have a specially marked set of jacks for a "phono input." Since CDs, DVDs, tape decks and TV line outputs all match the same electrical specifications, they can be interchanged in any of the receiver’s line inputs. For example, a tape deck can be plugged into a jack marked "CD." If you have a DVD player but your stereo receiver does not have an input marked "DVD," you can plug the DVD audio into the CD, tape or "Aux" (auxiliary) inputs.

Enhance the sound of your television viewing by connecting the audio outputs from a TV, DVD, VCR, satellite receiver or even a video game to the stereo receiver’s line inputs. TV speakers are notoriously poor in quality compared to those found with even a modest stereo receiver and speaker combination. When connecting components such as these that also have a video output, connect the video output of the device to the video input on the TV and connect the two audio outputs to a line input on the receiver.

Match the specifications of the speakers to that of the receiver’s output. The two things to look for are "impedance" and power handling capabilities. Match the power output of the receiver closely with the speakers’ power handling ability. A 100-watt power amplifier should be connected to speakers that can handle 100 watts. Speakers whose maximum power handling is less than the amplifier run the risk of being damaged. Speakers that are rated significantly higher than the output of the amplifier may result in poor sound quality, as the amplifier has to work harder to drive the speakers.

Feel the bass in the sound coming from your receiver by connecting a subwoofer if your receiver has a designated subwoofer output jack. Subwoofers are specially-designed speakers that reproduce the lowest frequencies in the audio spectrum.

Audiophiles often purchase an "equalizer" to use with their receivers. While receivers have treble and bass controls, an equalizer allows volume adjustment of much finer frequency bands, which can compensate for room acoustics. Equalizers must be inserted between the input source and the input of the amplifier. This is done by using the "Tape In" and "Tape Out" jacks on the receiver. The equalizer has jacks and a switch on it to allow tape decks to be connected, since it occupies the tape jacks on the receiver.

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