23TECHNICALLY SPEAKING continued

even risk overloading your speakers. You can only adjust the bass and treble controls on the front panel. However, you can compare the sound with the tone controls on or off by pressing the Tone button on the front panel or remote control.

DC Trigger Input Jack

The P 3 can be turned on automatically when a trigger voltage is received from an external source such as a system controller. The DC Trigger circuit can be activated with a DC voltage from between +9 Vdc to + 12 Vdc and requires only 0.2 mA of current to activate. Use the provided gray color cable with 2.5 mm sub- mini plugs to connect the output of the DC trigger source to the P 3’s 12 V Trigger input. Depending on the component used to trigger the P 3 on, you may need to modify the DC trigger wire differently. To trigger properly, the positive voltage must appear at the tip of the 2.5 mm plug. The wire with the red stripe corresponds to the positive connection.

Note: When a live DC source is connected to the P 3’s 12 V Trigger Input jack, you cannot turn the P 3 off with its front panel On-Off button or remote control handset Off button.

DC Trigger Output Jack

The P 3 generates its own +12 Vdc voltage at the 12 V Trigger Out jack so you can trigger on other components.

External Remote Input and Loop Out

The External Remote input is for connection to a wired infrared repeater system or system controller. This input jack accepts a standard 1/8" (3.5 mm) two- conductor mini-plug with a positive tip and a negative sleeve. Your Authorized Parasound Dealer or Custom Installer can recommend a compatible infrared repeater system for the P 3.

The External Remote circuit has a loop output so you can connect an additional IR controlled component.

Front Panel Display

The display on the front panel indicates operational status of the P 3 including:

Source Selected

Volume Level of both channels

Muting status

Eliminating Hum and Buzz Caused by Ground Loops

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. Ground is supposed to remain at zero volts while the audio signal swings positive (voltage above ground) and negative (voltage below ground). If ground isn’t at zero, there can be an

audible 60 Hz hum (or 50 Hz hum in regions with 50 Hz AC). The harmonics of these frequencies (120 Hz, 240 Hz, 480 Hz or 100 Hz, 200 Hz, 400 Hz) may add buzz in addition to the hum.

The ideal of zero voltage ground for all the components in a system is practically impossible, because some resistance between the ground points of different components is inevitable. By keeping components close together with their power cords plugged into a common AC outlet or power strip, you’ll avoid the problems created by resistance in the house’s wiring.

Hum and buzz is also caused when unwanted voltage flows through multiple component ground points called ground loops. Here are three tips to avoid ground loops:

1.Use balanced input lines with your Parasound P 3. (See Balanced and Unbalanced Lines in this section).

2.When rack mounting, always use insulated “shoulder” 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. Extras are available from rack manufacturer Middle Atlantic Products, www.middleatlantic.com.

3.Use the ground switch on your power amplifier to eliminate most ground loops. This separates the amplifier’s signal input ground from its chassis ground to isolate unwanted voltage in the shields of the unbalanced (RCA) interconnect cables. Be sure your system installation is finished before you try moving the ground switch from its “Normal” to its “Lift” position.

Headphone Circuit

The P 3 includes a high-quality headphone amplifier. It is suitable for headphones with an impedance of 8 or higher. The headphone jack accepts a standard 1/8” (3.5 mm) 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.

Tape Record and Play Circuitry

The Tape Play/In and Rec/Out jacks on the P 3 enable you to connect a cassette deck or the analog input and output of a MiniDisc or CD recorder. You can also play back analog audio outputs from your computer’s sound card or MP3 player.

If you don’t have a recording device, you can use the P 3’s Tape Play/In jacks as an input for another line level source component. The P 3 bass and treble controls function only for playback, so you can’t use them when making recordings.