Parasound Halo C1 Controller manual Technically Speaking, The Tape Monitor and its Many Uses

TECHNICALLY SPEAKING 59

Balanced and Unbalanced

Analog Audio Connections

Recording and broadcast studios use balanced connec- tions almost exclusively because of balanced lines’ inher- ent ability to reject noise and hum, even when compo- nents are far apart and connected by long cables. Certain high-quality preamplifiers, amplifiers, and sur- round controllers built for residential use include bal- anced connections with XLR jacks for the same reasons.

The C 1’s balanced outputs enable you to take full advantage of the inherent noise-rejection capability and superior sound quality of Parasound Halo power amplifiers, especially when the amplifiers are mount- ed far away, near the speakers. The balanced input on the C 1 also ensures the best possible analog connec- tion to a source component having balanced output. And, for the purest possible sound, the C 1 has a Bypass mode that feeds the balanced audio input signal directly to the front left and right balanced outputs, with no processing except volume control.

The balanced jacks on the C 1 are wired according to the AES standard (shield on pin 1, positive on pin 2, return on pin 3). Should it ever be necessary for some reason to connect any of the C 1’s balanced jacks to unbalanced jacks on another component, you can make an adapter cable by wiring an unbalanced cable’s shield to pin 1 on an XLR connector, wiring the unbalanced cable’s center conductor to pin 2, and leaving pin 3 unconnected.

Unbalanced connections with RCA jacks are found on all home audio equipment. RCA jacks and two-conductor wires are less costly than the additional circuitry, higher priced XLR connectors and three-conductor wiring required for balanced connections. In an unbalanced line, the positive audio signal appears at the center pin of the RCA jack and the negative signal on the outer shield wire, which also functions as the ground connection. Unbalanced interconnect cables are vulnerable to hum from an AC line, or other noise, such as RFI (Radio Frequency Interference), which can be reproduced through your loudspeakers. Since the unbalanced line’s ground also carries the audio signal, there is no way for the connected amplifier or preamplifier to distinguish between the audio signals you want and unwanted noise emanating from external sources.

In balanced lines, the positive and negative audio signals are carried on separate conductors within a separately grounded shield that provides equal inter- ference-protection to each signal. The positive and negative audio each have opposite polarity with respect to ground, making them equal but 180° out of phase with each other. The input uses differential circuitry, which amplifies only the difference between the audio signals but not the elements they have in

common. For example, when a 1-volt signal arrives at a balanced input stage, the differential input “sees” a positive 1 volt minus a negative 1 volt, or 2 volts total. Any external hum and noise that somehow does get into a balanced line appears on both conductors but with opposite polarities. As a result, the input circuit simply cancels the noise out, a process known as common-mode rejection. One of the most important specifications for a differential circuit is its ability to reject signals common to both conductors. This is measured in dB and is called the common mode rejection ratio or CMRR.

The Tape Monitor and its Many Uses

The Tape Monitor Play/In and Rec/Out jacks on the

C 1 are designed for easy integration of a stereo ana- log recorder (tape, CD, MiniDisc, or even the inputs and outputs of your computer’s sound card). It is espe- cially useful with recorders that permit simultaneous playback of the just-recorded tape, enabling you to quickly compare the recorded output to the signal you’re recording, simply by pressing the “Tape” key on Page One of the Master remote’s C1/C2 menu.

The Tape Monitor jacks can also be used with equaliz- ers and other two-channel signal processors. If you connect the Rec/Out jack to the processor’s input, and connect the processor’s output to the Play/In jacks, you will be able to switch between the direct output of the C 1 and the output of the processor.

If you have so many components that you’re short of input jacks, the Play/In jack can also be used as an extra unbalanced analog stereo input. However, the signal from this input will not be available through any of the recording outputs or Zone.

Bass and Treble Controls

The bass and treble controls offer adjustment of overall tonal balance in the front left, center, and right channels. The Bass controls allow you to boost or cut low frequen- cies ±12 dB at 20 Hz, in 1-dB increments. The Treble controls allow you to boost or cut high frequencies ±12 dB at 20 kHz in 1-dB increments. To preserve sonic clarity, use these controls sparingly and only for record- ings that actually sound better with tonal correction. You will find that very slight adjustments can add a degree of warmth, richness, clarity and airiness. However, greater adjustments may obscure musical detail, and even risk overloading your speakers. You can only adjust the bass and treble controls via Page 3 of the C1/C2 menu on the Master remote.

Bass and treble controls do not affect the Rec/Out, Record 1, Record 2, or Zone outputs, but their effect can be heard when playing back through the Play/In input.

IR Repeater Input Jacks

The IR inputs (one for each zone) on the rear panel of