Sound advice: Defining a stereo receiver

Q: I read your recent column about receivers and amplifiers. I have a Sony Blu-ray equipped BDV-E500 Home Theater System. I don't have a receiver or amp, that is unless one is built into the Blu-ray system. Am I missing something? What is a receiver?

A: Your system has an A/V receiver with an integrated Blu-ray player. Any component with amplification, a volume control and a tuner can be called a receiver, and yours has all three.

There are different types of receivers available. I will start with a simple stereo receiver and go from there.

A stereo receiver combines three separate audio components on a single chassis with a shared power supply: an amplifier, a preamplifier and tuner. In the early days of audio, enthusiasts would purchase separate amplifiers, preamplifiers and tuners and connect them together.

Here is how they work, from the speakers backward:

The speakers are connected to the amplifier, which powers the speakers.

The amplifier is connected to a preamplifier. It switches between listening sources, changes volume and left-right balance and may incorporate bass and treble controls along with other ways to modify the signal. It then sends the signal to the amplifier. Obviously, it gets its name "preamplifier" because it comes before the amplifier.

In 1954, Harman/Kardon merged the three components and introduced the first compact stereo receiver, the Festival D1000. Today most receivers are Audio/Video, or A/V receivers because they have enough amplifier channels to drive five or more speakers in a surround sound system, as well as HDMI connections and digital decoding for surround sound formats.

Prices have not changed a great deal over the years despite these additional capabilities. In the late 1980s a high-quality, high-power receiver could easily cost $500 or more. You can now purchase high-quality A/V receivers for the same amount or less.

Notice that I said "high quality" and not "high power." To keep prices the same while adding features, the amplifier sections are typically where the manufacturers save the money. Most A/V receivers measure their power with only one or two channels in use. If you use all the channels simultaneously, power can drop significantly.

That is why when you see a separate home theater amplifier specification that says, "75 watts per channel, with all channels driven" it will be much more powerful than a receiver that also has a 75-watt rating. The manufacturer will be sure to mention that it achieves its power output to all channels to distinguish itself from a receiver's power rating.

There are other ways to combine the three essential components of amplifier, preamplifier and tuner. An amplifier and a preamplifier combined on the same chassis is an integrated amplifier. A joint preamplifier and a tuner is called a preamp/tuner, and an audio-video processor combined with a preamp is called a preamp-processor. Preamp-processors with separate amplifiers are found in the best high-end systems, rather than receivers.