Nad 925-THX Owners Manual

925THX

• OWNER’S MANUAL

• MANUEL D’INSTALLATION

• BEDIENUNGSANLEITUNG

• MANUAL DEL USUARIO

• MANUALE DELLE ISTR UZIONI

• BRUKSANVISNING

• MANUAL DO PROPRIETÁRIO

THE FOLLOWING PRECAUTIONS AND SAFETY INSTRUCTIONS ARE REQUIREMENTS OF UL AND CSA SAFETY REGULATIONS

ATTENTION:

RISQUE DE CHOC ELECTRIQUE

NE PAS OUVRIR

CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE COVER OR BACK)

ATTENTION: AFIN DEVITER UN CHOC ELECTRIQUE ET LES CONEQUENCES GRAVES OUI

POURRAIENT EN RESULTER, TENTEZ PAS D’OUVRIR L’APPAREL ET DE TOUCHER AUX

COMPOSANTS INTERNES SANS LA PRESENCE D’UNE SERVICE PERSONNEL

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC

SHOCK, DO NOT EXPOSE THIS UNIT TO RAIN OR MOISTURE.

The graphic symbol of a lightning flash with arrow point within a triangle signifies

that there is dangerous voltage within the unit and it poses a hazard to anyone

removing the cover to gain access to the interior of the unit. Only qualified

personnel should make any such attempt.

The graphic symbol of an exclamation point within an equilateral triangle warns

the user of the device that it is necessary to refer to the instruction manual and

its warnings for proper operation of the unit.

Do not place this unit on an unstable cart, stand or tripod, bracket or table. The unit may fall, causing serious injury to a child or adult and serious damage to the unit. Use only with a cart, stand, tripod, bracket or table

recommended by the manufacturer or sold with the unit. Any mounting of

and should use a mounting accessory recommended by the manufacturer. An appliance and cart combination should be moved with care. Quick stops, excessive

force and uneven surfaces may cause the appliance and cart combination to overturn.

this unit. Retain this notice and the owner’s manual for future reference.

laundry tub, in a wet basement or near a swimming pool.

proper ventilation. For example, it should not be situated on a bed, sofa, rug or similar surface that may block the ventilation openings; or placed in a built-in installation, such as a bookcase or cabinet, that may impede the flow of air through its ventilation openings.

stoves or other devices (including amplifiers) that produce heat

quency marked on its rear panel.

pinched, especially near the plug, convenience receptacles, or where the cord exits from the unit

other solvents for cleaning. Use only a soft damp cloth.

be unused for a long period of time.

enclosure through any openings.

the device on a wall or ceiling should follow the manufacturer’s instructions

Read and follow all the safety and operating instructions before connecting or using

All warnings on the unit and its operating instructions should be adhered to. Do not use this unit near water: for example, near a bath tub, washbowl, kitchen sink,

The unit should be installed so that its location or position does not interfere with its

The unit should be situated away from heat sources such as radiators, heat registers,

The unit should be connected to a power supply outlet only of the voltage and fre-

The power supply cord should be routed so that it is not likely to be walked on or

Unplug the unit from the wall outlet before cleaning. Never use benzine, thinner or

The power supply cord of the unit should be unplugged from the wall outlet when it is to

Care should be taken so that objects do not fall, and liquids are not spilled, into the

This unit should be serviced by qualified service personnel when: (1) The power cord or the plug has been damaged; or (2) Objects have fallen, or liquid has been spilled into the unit; or (3) The unit has been exposed to rain or liquids of any kind; or (4) The Unit does not appear to operate normally or exhibits a marked change

in performance; or

(5) The device has been dropped or the enclosure damaged.

DO NOT ATTEMPT SERVICING OF THIS UNIT YOURSELF. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.

Upon compIetion of any servicing or repairs, request the service shop’s assurance that only Factory Authorized Replacement Parts with the same characteristics as the original parts have been used, and that the routine safety checks have been performed to guarantee that the equipment is in safe operating condition.

REPLACEMENT WITH UNAUTHORIZED PARTS MAY RESULT IN FIRE. ELECTRIC SHOCK OR OTHER HAZARDS.

CAUTION: TO PREVENT ELECTRIC SHOCK, MATCH WIDE BLADE OF PLUG TO WIDE SLOT, FULLY INSERT.

ATTENTION: POUR EVITER LES CHOCS ÉLECTRIQUES, INTRODUIRE LA LAME LA PLUS LARGE DE LA FlCHE DANS LA BORNE CORRESPONDANTE DE LA PRISE ET POUSSER JUSQU’AU FOND.

If an indoor antenna is used (either built into the set or installed separately), never allow any part of the antenna to touch the metal parts or other electrical appliances such as a lamp, TV set etc.

CAUTION - POWER LINES: ANY OUTDOOR ANTENNA MUST BE LOCATED AWAY FROM ALL POWER LINES.

OUTDOOR ANTENNA GROUNDING

If an outside antenna is connected to your tuner or tuner-preamplifier, be sure the antenna system is grounded so as to provide some protection against voltage surges and built-up, static charges. Section 810 or the National Electrical Code ANSl/NFPA NO. 70-1984, provides information with respect to proper grounding of the mast and supporting structure, ing conductors, location of antenna discharge unit, connection to grounding electrodes and requirements for the grounding electrode.

(1.Omm

from 4-6 feet (1.22 - 1.83m) apart.

when a separate antenna-grounding electrode is used. See NEC Section 810-21 (j).

grounding of the lead-in wire to an antenna discharge unit, size of ground-

(1) Use No.10 AWG (5.3mm

) copper-clad-steel or bronze wire, or larger, as a ground wire.

(2) Secure antenna lead-in and ground wires to house with stand-off insulators spaced

(3) Mount antenna discharge unit as close as possible to where lead-in enters house.

(4) Use jumper wire not smaller than No.6 A WG (13.3mm

) copper, No. 8 AWG (8.4mm2) aluminium. No. 17 A WG

) copper, or the equivalent

EXAMPLE OF ANTENNA GROUNDING AS PER NATIONAL ELECTRICAL CODE INSTRUCTIONS CONTAINED IN ARTICLE 810 RADIO AND TELEVISION EQUIPMENT .

GROUND CLAMP

POWER LINES

SERVICE ENTRANCE CONDUCTORS

SERVICE ENTRANCE EQUIPMENT

POWER SERVICE GROUNDING ELECTRODE SYSTEM (e.g. Interior metal water pipe)

NOTE TO CATV SYSTEM INSTALLER: This reminder is provided to call the CATV

installer’s attention to Article 820-22 of the National Electrical Code that provides guidelines for proper grounding and, in particular, specifies that the ground cable ground shall be connected to the grounding system of the building, as close as possible to the point of cable entry as practical.

GROUND CLAMPS

GROUND WIRE

BONDING JUMPER

a, b

GROUND CLAMPS

OPTIONAL ANTENNA GROUNDING ELECTRODE. DRIVEN 8 FEET (2.44M) INTO THE EARTH IF REQUIRED BY LOCAL CODES. SEE NEC SECTION 810.21(f).

GROUND WIRE

STAND-OFF INSULATORS

MAST

ANTENNA LEAD-IN WIRE

ANTENNA DISCHARGE

UNIT

a, b

TO EXTERNAL ANTENNA TERMINALS OF PRODUCT

Owner’s Manual 5 - 7

Manuel d’Installation 8 - 10

Bedienungsanleitung 11 - 13

Manual del Usuario 14 - 16

Manuale delle Istruzioni 17 - 19

Bruksanvisning 20 - 22

Manual do Proprietário 23 - 25

Rear Panel Connections

2 4 53

Front Panel Controls

1 2

Figure 1

120V version only

About the 925THX

Designed specifically for home theater and custom installation set-ups, the NAD 925THX Power Amplifier delivers uncompromising performance. It combines supreme reliability, flexibility, and performance with outstanding value.

Flexibility has always been an important part of NAD components. Such flexibility is particularly important in home theater and other multi-channel systems. That’s because it is common for a multi-channel system to incorporate different brands and models of loudspeakers. Often these speakers have different levels of efficiency . The individual input level controls for the five channels of the NAD 925THX make it easy to compensate for such differences in efficiency, and achieve the ideal system balance.

Ample dynamic headroom of the 925THX ensures that the very wide dynamic range of modern cinema soundtracks and digital music sources will be preserved. In addition, the 925THX will handle low impedance speakers with ease.

The 925THX incorporates NAD’s unique Soft-Clipping circuitry in all five channels. Any amplifier can be overdriven if it is played too loud, exceeding the maximum output power. Under such circumstances, amplifiers produce extreme high levels of distortion which, besides sounding very unpleasant, can damage your loudspeakers. The Soft Clipping circuit suppresses such distortion and minimizes the risk of damage to speakers. This is particularly important with movie soundtracks which often contain very dynamic outbursts in which, unlike music, it is difficult to hear this potentially damaging distortion. Five status LED’s on the front panel illuminate when the Soft Clipping circuit is engaged. Soft Clipping can be defeated with a rear panel switch.

The design:

The NAD 925THX houses five individual amplifiers, each on separate circuit board. Each amplifier channel acts as a “mono block” within the chassis. Each input connector, and set of loudspeaker output terminals, is directly connected to that channel’s circuit board. This design eliminates extra wiring and keeps signal paths short. Furthermore, this modular design increases reliability and thermal efficiency.

The input circuit uses a totally new dual differential

input topology that operates in true Class-A mode.

The special Holmgren™ toroidal transformer has less hum and magnetic leakage than conventional toroidal transformers, but retains the usual benefits of high efficiency and high power-to-weight ratio.

Ruggedness and reliability are critical in custominstalled systems. The 925THX uses a combination of fuses and non-intrusive electronic protection. This provides highly effective protection that does not effect audio performance. Each channel is protected against excess temperature, DC fault and loudspeaker short-circuit. The 925THX’s inherently conservative, high-voltage/high-current output stage has been designed for years of trouble-free service.

NAD was the first company to introduce a THX certified power amplifier . In that tradition, the 925THX easily passes Lucas Films’ stringent THX performance requirements. As a result the NAD 925THX will handle the most demanding signals with ease, and yet preserve every subtle audio detail in the most demanding THX and Dolby Surround systems.

Installation Precautions

WARNING – To reduce the risk of fire or electrical

shock, do not expose the amplifier to rain or moisture.

CAUTION – For units factory-set at 115 volts AC match the wide blade of the power plug to the wide slot of the power outlet, to prevent electrical shock. Be sure the plug is completely inserted into the receptacle.

Turn off all the components in the system whenever connecting or disconnecting any audio signal wiring. Once all signal connections have been completed, turn down all the system’s main volume control before turning the system components on. Then increase the volume control setting carefully to avoid damage to the system components.

Notes on Installation Location

Read and follow all the safety instructions on the

first page of this manual.

To prevent a fire or shock hazard, do not place the amplifier where it will be exposed to any water or moisture. If liquid is accidentally gets into the amplifier, immediately unplug the AC power cord. Do not operate the amplifier again until it has been examined by a service technician.

The amplifier generates a moderate amount of heat, requiring ventilation. Do not obstruct the air outlet grilles on the top or bottom covers. There should be at least 3 inches (7.5 cm) of clearance above the amplifier and 1 inch (2.5 cm) to the sides. Do not place the amplifier in an enclosed area, such as in a bookcase or in a cabinet, unless it is very well ventilated. Be sure there is adequate room behind the amplifier for signal input and speaker output connections. If you want to locate the amplifier on a carpeted floor, place a board under it in order to prevent it from sinking into the carpet, blocking the air inlets on the bottom.

Do not place the amplifier where it will be exposed to direct sun light for prolonged periods of time.

This unit may be installed on any sturdy, level surface. NOTE: The amplifier’s weight must always rest on its bottom feet. Never put the amp down on its rear panel, with its front panel facing up. Doing so risks damage to the input/output connectors.

Rear Panel Connections/Controls

1. AC Line Cord

Plug the AC line cord into a nearby wall outlet that provides the correct AC power line voltage, as indicated on the back panel of the unit. Do not plug the amplifier into a convenience outlet on your preamp. The amplifier requires more power than these outlets typically can provide.

2. Inputs

Each of the five independent power amplifiers within the 925THX has its own signal input connector. Before making any connections to the amplifier, make sure the POWER is switched OFF.

Connect the signal cables from the preamplifier, surround sound decoder or other signal source to these inputs.

3. Input Level Controls

The amplifier is equipped with separate input level controls for each channel. Before turning on the 925THX for the first time, make sure all level controls are in their normal full-clockwise position.

Under some circumstances, other settings may be useful for:

(1). Level-matching – In systems that incorporate speakers of varying efficiencies, it may be necessary to reduce the settings of some controls to achieve proper channel-to-channel balance.

The power transformer in the 925 generates a magnetic hum field of moderate strength. Turntables (especially those with a moving-coil pickup cartridge) should not be located near the amplifier. Magnetic media, such as audio or video tapes and computer diskettes, should not be stored near the amplifier.

(2). Extended volume-control range – Many stereo systems have so much voltage gain that the speakers (or your ears) are over-driven at any volume-control setting higher than 1 1 or 12 o’clock position of the volume control. As a result you can use only the lower half of the volume control’s range, where adjustments are imprecise and channel-balance errors tend to be greater . If all input level controls are reduced, you can turn up your preamplifier’s volume control, making effective use of most of its range. (Suggestion: adjust the input level controls so that your preferred maximum sound levels occur at about 2 or 3 o’clock on the volume control.)

As an added benefit, this procedure suppresses any noise produced by the preamp’s high-level circuitry (e.g. any residual hum or hiss that does not go away when the Volume is turned down).

4. Speaker Connections

This amplifier is equipped with special high-current binding-post speaker terminals. Connect the loudspeakers with heavy-duty (16-gauge or thicker) braided wire. Connections may be made in either of two ways. [See Figure 1.*]

(1) Strip off a half-inch (1 cm) of insulation from each speaker wire. In each conductor, twist the thin strands of wire together. Unscrew the knob, insert the bare wire into the opening at the base of the binding post, and tighten the knob until it grasps the wire securely . Check to be sure that there are no loose strands of wire touching the chassis or an adjacent terminal.

(2) Install banana plugs on your speaker wires, and plug them into the end of each binding post. The terminals are separated by 3/4 inch (l9mm), so they will accept dual-banana plugs.*

NOTE - Speakers must operate in phase with each other in order to produce a proper stereo image and to reinforce rather than cancel each other’s output at low frequencies. When connecting speakers, take care that the red (positive) terminal on each loudspeaker is connected to the corresponding red (positive) terminal on the amplifier.

Front Panel Controls

1. Power Switch

Press this button to switch the amplifier on or off. A green LED next to the power button illuminates when the power is on.

2. Soft Clipping Lights

When the Soft Clipping circuit of the 925THX is activated the indicator LED’s on the front panel will light.

5. SOFT CLIPPING

When an amplifier is driven beyond its specified power output it normally produces “hard clipping” or distortion of the signal. Such hard clipping, in addition to sounding unpleasant, can damage the speakers in the system. The NAD Soft Clipping circuit gently limits the output waveform, minimizing audible distortion and reducing the change of speaker damage when the amplifier is overdriven.

We recommend that the Soft Clipping switch on the back panel of the 925THX be left in the ON position when system is being operated at levels that might exceed the amplifier’s power capacity.

A propos du 925 THX

Spécialement conçu pour les chaînes sur mesure et pour les auditoriums à domicile, l’Amplificateur de Puissance NAD 925THX délivre des performances sans égal. A un rapport qualité/prix exceptionnel il associe une fiabilité, une souplesse et des performances incomparables.

La souplesse a toujours été un critère essentiel pour les composants NAD. Une telle souplesse est particulièrement importante pour les chaînes de type auditorium à domicile et les autres chaînes multi-voies, car une chaîne multi-voies comporte souvent des haut parleurs de marques et de modèles différents. Ces haut parleurs sont souvent caractérisés par des rendements différents. Les commandes individuelles de niveau d’entrée pour les cinq voies du NAD 925THX permettent de compenser sans problème ces différences de rendement et d’amener le système à l’équilibre idéal.

La vaste échappée dynamique du 925THX garantit un rendu parfait de la totalité de la plage dynamique très étendue des bandes son du cinéma moderne et des sources de musique numériques. De plus, le 925THX n’a aucun problème pour s’adapter à des haut parleurs basse impédance.

Le circuit d’écrêtage doux (Soft Clipping), unique à NAD, équipe les cinq voies du 925THX. T out amplificateur peut être poussé au-delà de ses limites et de sa puissance maximale si le volume est trop fort. Dans ces cas là, les amplificateurs produisent des niveaux extrêmes de distorsion qui, outre le fait qu’ils sont très désagréables à entendre, peuvent endommager les haut parleurs. Le dispositif d’écrêtage doux (Soft Clipping) supprime ces distorsions et réduit les risques de détérioration des haut parleurs. Cette fonctionnalité s’avère plus particulièrement utile pour les bandes sons des films qui comportent souvent des éclats très dynamiques pour lesquels, contrairement à la musique, la distorsion potentiellement préjudiciable pour les haut parleurs est difficilement audible. Cinq diodes électroluminescentes sont prévues sur la face parlante de l’amplificateur, et s’allument lorsque le dispositif d’écrêtage doux est actif. Il est possible de couper l’écrêtage doux grâce à un interrupteur sur la face arrière.

La conception :

Le NAD 925THX comporte cinq amplificateurs individuels, chacun étant implanté sur sa propre carte à circuit imprimé. Chaque voie d’amplificateur constitue un ensemble distinct à l’intérieur du châssis. Chaque connecteur d’entrée et chaque jeu de bornes de sortie haut parleurs est relié directement à la carte correspondant à sa propre voie. Cette configuration évite les câblages superflus et garantit que le chemin parcouru par les signaux est le plus court possible. En outre, cette conception modulaire augmente la fiabilité et le rendement thermique.

Le circuit d’entrée est basé sur une topologie d’entrée double-différentielle entièrement nouvelle, qui fonctionne en véritable mode de Classe A.

Grâce au transformateur toroïdal Holmgren™ spécialement conçu, l’amplificateur bénéficie d’une réduction du bourdonnement et des fuites magnétiques par rapport aux transformateurs toroïdaux traditionnels, tout en conservant les avantages classiques de ce type de transformateur, c’est à dire un très bon rendement et un rapport puissance/poids élevé.

La robustesse et la fiabilité sont des facteurs critiques quand il s’agit de chaînes installées sur mesure. Le 925THX utilise une série de fusibles et une protection électronique sans intrusion. Cela permet d’assurer une protection très efficace sans affecter les performances audio. Chaque voie est protégée contre les surtempératures, les pannes de courant continu et les courts-circuits. L’étage d’entrée haute tension / haute intensité du 925THX, conservateur de par sa conception, est prévu pour fonctionner des années sans aucun problème.

NAD a été la première société à mettre sur le marché un amplificateur de puissance certifié THX. En accord avec cette tradition, le 925THX respecte sans aucune difficulté les exigences de performances THX très rigoureuses de Lucas Films. Par conséquent, le NAD 925THX est capable de traiter les signaux les plus exigeants sans aucune difficulté, mais permet néanmoins de reproduire chaque subtilité audiophonique au sein des systèmes THX et Dolby Surround les plus exigeants.

Précautions d’installation

ATTENTION DANGER - Afin de réduire le risque

d’incendie ou de choc électrique, ne pas exposer l’amplificateur à la pluie ou à l’ humidité.

ATTENTION - Pour les ensembles réglés sur 1 15 V olts CA à l’origine, faire attention d’insérer la fiche plate large de la prise d’alimentation dans la fente large de la prise de secteur murale, ceci afin d’éviter les chocs électriques. Veiller à ce que la prise d’alimentation soit bien enfoncée dans la prise de secteur murale.

Avant de procéder à un quelconque branchement ou débranchement des câbles de signaux audio, il faut impérativement mettre hors tension tous les éléments de la chaîne. Après avoir effectué tous les branchements des signaux, régler au minimum toutes les commandes principales de volume sonore de la chaîne avant de mettre les différents modules sous tension. Augmenter alors progressivement le volume sonore afin d’éviter toute détérioration des éléments de la chaîne.

+ 18 hidden pages