Hafler 0915P manual Additional Information

HEADPHONE AMPLIFIER

Internal signal grounding has been carefully routed to follow the signal path from the input jacks, through the Selector System, through the Volume and Balance Controls, and finally to the line amplifier. All power supply ground paths are returned to a single “star” ground point at the power supply to minimize ground modulations. Extensive use of ground planes and interchannel shields maximize inter-channel separation.

For units wired for 100-120 VAC, the power supply is kept “on” at all times so that all circuitry is maintained at optimum operating temperature, for maximum fidelity as soon as the system is used. The front panel Power Switch operates the Switched Outlets only, to turn on associated system components.

For

units wired

for

200-240

VAC,

the

Power Switch controls the preamplifier’s power supply. This

switch

may

be

left “on” at all times, if

desired,

to

maintain

optimum

operating

temperature.

The

Headphone

Amplifier utilizes

a

separate high-slew

rate

operational

amplifier

to

drive

the

high

current

demands

of

headphone operation.

This relieves the Line Amplifier

from the additional

burden

of driving difficult headphone loads, and

leaves the

main signal path

uncompromised

for signals

to

power

amplifiers.

The

Output

Off

Switch turns

off

both

line

outputs,

to

be

used

when

listening to

headphones

only, or

as

a

system muting

switch.

ADDITIONAL INFORMATION

INSTALLING PHONO OPTION

If the 915 Preamplifier was purchased without the Phono Option, the							Phono/Aux 1 input is a	line level
input, and	cannot be used with a	turntable.	To	convert this input			for use with a turntable, purchase
the 915 Phono Option Accessory from your			Hafler Dealer. Review the installation instructions before
attempting this procedure. If any doubts exist			about		one’s	ability	to install the Phono	Option, it is
advisable	that the procedure be	conducted	by	a	qualified	technician.

WARNING! UNPLUG THE UNIT FROM AC POWER BEFORE ATTEMPTING THIS PROCEDURE. FAILURE TO DO SO CAN RESULT IN SEVERE ELECTRICAL SHOCK AS WELL AS DAMAGE TO THE PREAMPLIFIER AND/OR PHONO BOARD.

1)

Place

the

preamplifier

on a soft, protective surface. Remove

the

eight allen

head

screws

(four

on each

side),

and

six phillips head screws

(three

each

on top

and

bottom), securing

the

top

and

bottom covers. Remove covers. Carefully remove

the

plastic

plug

covering

the

MC/MM

switch

hole

by

squeezing the prongs inside the chassis

and prying out the plug.

2)

Find

the

three wire jumpers on the main printed circuit board, located near the Phono/Aux

input

jacks,

labelled

RJ5,

RJ7, and RJ8. Remove the

three

jumper wires as

shown.

These

jumpers

may

be

de-soldered

or

clipped

out.

3)

Refer

to

the

diagram

“Installation

Of

Optional Phono

Printed

Circuit

Board”.

Push

the

MC/MM

switch to

the “in” position to ease installation of the phono board. Carefully

guide

the phono

board

onto

the

main

board,

checking to make sure that all the electrical connector pins are aligned

with

their

mating

parts

before

completely

seating

the

phono

board

onto

the

three plastic standoffs.

It should snap into place with no free play. Double check that all four pins of each of three

connectors

have

been

inserted

completely.

If some

of

the

pins

have not properly seated, squeeze the prongs

of the

three

plastic

stand-

offs

to

release

the

phono board. Straighten any bent pins before

re-attempting

installation.

4)

Add

the

button to the shaft of the MC/MM switch. Unless modifying

the

cartridge

loads

at

this

time,

replace

the

covers. (See

Installing Cartridge

Loads).

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