Audio Research Reference 750 Manuel du propriétaire télécharger pdf (Page 6)

of your support system to be sure it is rated to

handle this weight.

If the unit is to be operated in an enclosure such as

an equipment rack, make certain that adequate

air flow above and to each side of the unit is

provided. The “ambient” operating temperature

should never exceed 120º F or 49º C. Additional

ventilation can be provided by fan-cooled,

perforated tube covers available for purchase

through your Audio Research dealer. If these

covers are used, do not place paper, wood, or any

other objects on top of the cover that could

obstruct cooling or create a fire hazard. Improper

installation will cause premature tube failure and

will affect your warranty, as well as the service life of

the unit. Keep children and pets away from

exposed tubes at all times to prevent possible burns

or injury.

It is normal for a vacuum tube power amplifier to

run quite “warm”, and if used for prolonged

periods, “hot” to the touch. All components within

are, however, operated at safe, conservative levels

and will not be improperly affected thereby,

providing the requirements outlined above are

adhered to.

Warnings

1. To prevent fire or shock hazard, do

not expose this product to rain or

moisture.

2. This unit operates on voltages which can cause

serious injury or death. Do not operate with top

cover or side panels removed. Any necessary

servicing should be carried out by your authorized

Audio Research dealer or other qualified

electronics technician.

3. Use only the plastic insulated screwdriver

included with this unit when making front panel

bias adjustments.

4. The power cord on this unit is safety-tested and is

equipped with a proper grounding plug. If used

normally, it will provide a safe earth ground

connection of the chassis. Defeat of the

grounding plug, or any unauthorized modification

of the active circuitry or controls of this unit,

automatically voids warranty coverage,

5. For safe operation and protection against fire

hazard, replace fuses only with those of the same

type and rating as those supplied with this unit.

6. At 170 lbs. (77.2 Kg) net weight per chassis, the

Reference 750 amplifier is too heavy for one

person to lift. To avoid injury, do not attempt to

unpack, lift or move the unit without the help of at

least one other person.

7. Always mute the preamplifier when cueing a

phono cartridge stylus up or down.

Due to the immense power supply reserves, high

power output, and wide bandwidth of the

Reference 750, added emphasis must be placed

on use of your preamplifier's mute switch from a

safety standpoint. A transient signal burst or “pop”

such as caused by tonearm cueing, accidental

dropping or brushing of the phono cartridge stylus–

even at a normal listening level–could cause an

instantaneous peak power demand on the

amplifier of up to 1000 watts (which the Reference

750 will try to deliver). The importance of lowering

the preamplifier volume level to a minimum setting

and activating the mute switch whenever cueing

the tonearm or making contact with the phono

cartridge stylus cannot be overemphasized.

Adhering to this precautionary muting procedure is

equally important when turning your system on or

off, and when connecting or disconnecting any

cables in the system. Carefully following this

recommendation will minimize the chance of

causing undue stress and potential damage to your

amplifiers and loudspeakers. (See your preamplifier

Owner's Manual for more detailed instructions on

use of muting provisions.)

Description of Controls

POWER: Press the POWER switch to turn the unit on,

indicated by a lit green LED directly above the

switch. When turned on, there is an automatic

warm-up sequence which lasts for approximately

45 seconds before the unit is operational.

FAN: Press the FAN switch to select low (dim Power

LED) or high (bright Power LED) for fan speed

setting. Only applicable to installed optional top

cover with ventilation fans.

LIGHT: Press the LIGHT switch to select high, low, or

no meter illumination.

BIAS (Adjustment Procedure):

NOTE: Amplifier should be turned on and operating

for at least 30 minutes prior to adjusting bias of the

output tubes.

Press BIAS switch once and the V1 output tube LED

is illuminated with its bias level indicated on the

front panel meter. Adjust V1 tube bias level with

the plastic flat-bladed bias tool (provided), inserted

in the V1 SET hole in the front panel so the meter

reading is in the center of the labeled bias range.

Press BIAS switch again to check V3 tube bias level

which should be within the bias range arc. Press

the BIAS switch repeatedly and check the V5, V7,

V9, V11, V13 and V15 tube bias levels in the same

way. Note that each of the odd V number the

tube bias levels are controlled by the V1 bias

setting.

Press the BIAS switch once more to read and adjust

V2 tube bias level with the bias tool in the V2 SET

1 2 3 4 5 6 7 8 9 10

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Audio Research Reference 750 Manuel du propriétaire Page 6

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