Parasound Halo C1 Controller manual Technically Speaking, Preventing or Minimizing Hum and Buzz

60TECHNICALLY SPEAKING continued

the C 1 are used for connecting the C 1 to wired infrared repeater sensors or system controllers. Note that the main and remote zones each have their own IR input jacks.

The IR input jacks accept standard 1⁄8" (3.5 mm) two- conductor mini-plugs, with the positive wired to the plug’s tip and the negative to its sleeve. Your Authorized Parasound Dealer or custom installer can recommend a compatible infrared repeater system for the C 1.

Preventing or Minimizing Hum and Buzz

Audible hum and buzzing noises in a system are usually related to issues with the component grounds. Ground (sometimes called common) is a point of reference for voltages in virtually all audio and video components. Every component has its own ground reference, and the audio signal swings positive and negative in relation to that. Problems occur when components with slightly different grounds are connected together. Such “ground loops” allow unwanted voltages to flow between the components. This causes an audible hum at the fre- quency of the local power line (60 Hz in the U.S. and many other countries, 50 Hz in Europe and elsewhere). Harmonics of the power-line frequency (120, 240,

and 480 Hz in 60-Hz countries such as the U.S.A., or 100, 200, and 400 Hz in 50-Hz countries) may add buzz to the hum.

Here are three tips to avoid hum and buzz:

1.Keep the components in your system close togeth- er, with their power cords plugged into a common AC outlet or power strip, to avoid problems created by resistance in the house’s wiring.

2.Use balanced input and output lines with your Parasound C 1. (See Balanced and Unbalanced Lines in this section).

3.When rack mounting, always use insulated “shoul- der” washers. These break the ground loops caused by metal-to-metal contact between the rack, the units, and their rack-mount bolts. Washers are included in Parasound rack mount kits, and extras are available from Parasound.

Headphone Circuit

The C 1 includes a high-quality headphone amplifier. It is suitable for headphones with an impedance of 8 ohms or higher; with headphones of lower impedance (if any exist), volume may be unacceptably low.

The headphone jack accepts a standard 1⁄8" (3.5 mm) stereo mini-jack. If your headphones have a 1⁄4" jack, you will need a stereo 1⁄4" jack-to-stereo 1⁄8" mini-plug adapter.

Video Signal Formats

The C 1 can handle the three common video signal formats: composite video outputs, S-Video, and component video.

Composite video combines all the components of the video signal and passes them through a two-conduc- tor cable. It therefore offers the least vivid and detailed video images. It is, however, the most widely used home video connection standard, largely because it is the oldest. In the C 1, composite video input signals are fed only to the composite video out- puts. RCA connectors, usually yellow, are used almost universally for this format.

S-Video, which uses separate wires for luminance (pic- ture brightness – in effect, the signal portions that make a black-and-white picture) and chrominance (color information). Keeping these picture elements separate reduces interactions between them and produces a cleaner, more detailed picture than composite video. It also requires the use of connectors with four pins, two each for the luminance and chrominance circuits.

Component video, which requires three cables is capable of handling all current high-definition televi- sion (HDTV) formats, up to 1080i (1080 lines, inter- laced), and beyond.

The key to the high quality of component video con- nections are that they include separate links connec- tions for the video signal components of luminance

(Y)and color difference (Cb and Cr) rather than trans- mitting them mixed together and separating them out later. (Not every source component or video monitor labels its component video Y, Cb, and Cr; some may label their connections as be Y, B–Y, and R–Y or Y, Pb, and Pr. Refer to the owner’s manual of your video component for details.)

A growing number of video components, (including large-screen TVs, video projectors, and DVD players) have component video connections, and you’ll get the best possible picture quality if you use these connec- tions. However, you will need both a component video source (the C 1 has inputs for three such sources) and a TV or projector with component video inputs, as the

C 1’s component video board is isolated from its other video circuitry. Component-video systems commonly use RCA or twist-on BNC connectors, with BNC offering a slight edge in picture quality; the C 1 has BNC jacks, and comes with adapters for cables with RCA plugs.

In addition to these three jacks, which you’ll find on home theater components, and some professional video gear may have RGB connections, which use separate cables for red, green, and blue, plus external connections for horizontal and vertical sync signals (or, sometimes R, G and B plus a composite sync), as do the VGA video inputs and outputs on computers; the five jacks on the component video inputs and output of the C 1 can be connected to these components, too.