Hafler 915, 0915P User Manual

Haflee

HOME AUDIO COMPONENTS

I E R

Series 915 Preamp

Series

P R E A M P L I F

0915

NOTICE - IMPORTANT SAFETY INFORMATION

The lightning flash with arrowhead symbol within
an equilateral triangle is intended to alert the

user to the presence of uninsulated “dangerous

RISK OF ELECTRIC SHOCK

00 NOT OPEN

A

voltage” within the product’s enclosure, that may
be of sufficient magnitude to constitute a risk of

electric shock to persons.

WARNING: TO PREVENT FIRE OR

SHOCK HAZARD, DO NOT EXPOSE THIS

EQUIPMENT TO RAIN OR MOISTURE.

1.

READ INSTRUCTIONS

All the safety and operating instructions of your Hafler equipment should be read before power is applied to the
equipment.

2.

RETAIN OWNERS MANUAL

These safety and operating instructions should be retained for future reference.

HEED WARNINGS

3.
All warnings on the equipment and in the operating instructions are important and should be followed.

FOLLOW INSTRUCTIONS

4.
All operating and use instructions are important and should be followed.

HEAT

5.
The equipment should be kept away from areas of high temperature, such as heater vents, radiators, stoves/ovens,
fireplaces, etc.

6.

VENTILATION

The equipment should be used in an area suitable for proper ventilation. Care should be taken not to impede airflow
in and around the cabinet. Do not mount on a carpeted shelf or in a sealed enclosure. Allow for proper clearance above

the equipment.

A

I

0

The exclamation point within an equilateral
triangle is intended to alert the user of the

presence of important operating and mainte­nance (servicing) instructions in the literature
accompanying the appliance.

WATER AND MOISTURE

7.
The equipment should not be used in or around water, such as a bathtub, sink, or swimming area. Also, the equipment
should not be used in areas prone to flooding, such as a basement.

POWER SOURCES

8.
The equipment should be connected only to a power source of the same voltage and frequency as that listed on the

rear panel above the power cord entry point.

9.

POWER CORD PROTECTION

Power cords should be arranged so that they do not interfere with the movement of objects in the room: people, fan
blades, utility carts, etc. Also, care should be taken that the cord is not pinched or cut, and placed so that it is not in
danger of being pinched or cut, as in under a rug, around a tight corner, etc.

10. POWER CORD GROUNDING

The power supply cord is of a three wire grounded type, designed to reduce the risk of electric shock sustained from

a live cabinet. It is assumed to be of suitable length for most uses of the equipment. The use of extension cords and
power strips is discouraged unless they are of suitable rating to deliver the required total current for safe operation of
all connected equipment. Furthermore, extension cords or power strips must provide the same three wire grounded

connection. It is important that the blades of the equipment’s plug be able to fully insert into the mating receptacle.

Never remove the round grounding pin on the plug in an attempt to mate to a two wire ungrounded receptacle: use
a grounding adaptor with the grounding tab or wire suitably connected to earth ground.

-l-

11. NON-USE PERIODS

-2-

During periods of extended non-use, the power cord should be unplugged from the power source.

12. CLEANING

The equipment should be cleaned only as detailed in the operating instructions.

13. OBJECT AND LIQUID ENTRY

Care should be taken so that objects and/or liquids, such as cleaning fluids or beverages, are not spilled into the
enclosure of the equipment.

14. DAMAGE REQUIRING SERVICE
Hafler equipment should be serviced by qualified service personnel when:

A. The power supply cord or plug has been damaged, or

Objects have fallen, or liquid has been spilled into the equipment, or

B.

C. The equipment has been exposed to rain, or

D.

The equipment does not appear to operate normally or exhibits a marked change in performance, or

E.

The equipment has been dropped, or the enclosure has been damaged.

15. SERVICING

The user should not attempt to service the equipment beyond that which is described in the operating instructions. All
other service should be referred to qualified service personnel.

16. CARTS AND STANDS

The equipment should be used with carts or stands only of sufficient strength and stability for the use intended.
An equipment and cart combination should be moved with care. Quick stops and starts, excessive force, and

uneven surfaces may cause the equipment and cart combination to topple.

TABLE OF CONTENTS

PERFORMANCE SPECIFICATIONS

............................................................................................

General Information ...............................................................................................................

INSTALLATION

Rackmounting ........................................................................................................................

Ventilation/Placement ............................................................................................................

Line Voltage ...........................................................................................................................

OPERATION/CONNECTIONS

Power Cord Connection

Initial Power-Up/Muting

Convenience Outlets

........................................................................................................

System ............................................................................................

.............................................................................................................

Line Level Inputs ...................................................................................................................

Phono Section .......................................................................................................................

Front Panel View Diagram .....................................................................................................

Rear Panel View Diagram

Input/Record Output .....................................................................................................

Tape

Controls/Tone Switch ...................................................................................................

Tone

1,

Out

Control

Control

......................................................................................................................

.....................................................................................................................

2,

And Output Switch .........................................................................................

Output ..............................................................................................................

Section

Level

......................................................................................................................

Inpu?

Selector System

Buffer And Record Output Driver.. ............................................................................

Monitor Switching

And Balance Controls..

.....................................................................................................................

Control System

System .....................................................................................................................

.......................................................................................................................

Amplifier ...........................................................................................................

Volume

Balance

Out

Headphone

CIRCUIT DESCRIPTION

Phono
Line
J-FET
Tape
Volume
Line Amplifier..

Tone

Muting
Power Supply
Headphone

.....................................................................................................

.........................................................................................

........................................................................................................

............................................................................................

............................................................................................................

4

5

5
5

5

5

5
6
6
6
7
8
9
9
9

9
10
10

10
10

11

11
11

11

11
11

11

12

ADDITIONAL INFORMATION

Installing
Phono
Installing
Changing
Cartridge

Phono Option .......................................................................................................

Board Installation Diagram .......................................................................................

Cartridge Loads ....................................................................................................

Line Voltage Rating .............................................................................................

Loads Installation Diagram ..................................................................................

General Troubleshooting Hints ............................................................................................

Ground Loops

......................................................................................................................

Cleaning/Maintenance .........................................................................................................

Functional

Block Diagram ....................................................................................................

Main Board Parts List ..........................................................................................................

Main Board Component Layout Diagram
Main Board Circuit Schematic Diagram

............................................................................

...............................................................................

Phono Board Parts List ........................................................................................................

Phono Board Component Layout Diagram

..........................................................................

Phono Board Circuit Schematic Diagram ............................................................................

SERVICE POLICY AND LIMITED WARRANTY

.........................................................................

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.17
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.19
.20
.21
.22

.23

.24

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PERFORMANCE SPECIFICATIONS

PHONO SECTION

(Measured At

REC OUT)

All specifications are for 20 Hz - 20

FREQUENCY RESPONSE: +/-0.1
MAXIMUM OUTPUT: 5 volts RMS

TOTAL HARMONIC DISTORTION AND NOISE:

Moving Magnet:
Moving Coil:

SENSITIVITY (For 0.5 volts RMS at REC OUT, @ 1 kHz):
Moving Magnet: 6.0 mV RMS
Moving Coil: 600 uV RMS

SIGNAL TO NOISE RATIO (A-weighted, relative to 0.5 V RMS at REC OUT):
Moving Magnet: -87
Moving Coil: -80

MAXIMUM INPUT SIGNAL (@ 1
Moving Magnet: 65 mV RMS
Moving Coil: 6.5 mV RMS

INPUT IMPEDANCE:
Nominal: 47,000 ohms
Moving Magnet: 220 pF as supplied, user adjustable
Moving Coil: 100 ohms as supplied, user adjustable

.002%

.009%

dB

dB

dB

kHz):

kHz

unless specified otherwise.

LINE AMPLIFIER

(Measured at

OUT 1

or OUT 2)

HEADPHONE

AMPLIFIER

GAIN (@ 1
Moving Magnet: +38.5
Moving Coil: +58.5

FREQUENCY RESPONSE: +/- 0.1 dB (into 33,000 ohms)
BANDWIDTH: 8 Hz
MAXIMUM OUTPUT: 6 volts RMS

TOTAL HARMONIC DISTORTION AND NOISE:

SENSITIVITY (For 0.5 volts RMS Output): 45 mV RMS
SIGNAL TO NOISE RATIO (A-Weighted, relative to 2 volts RMS output): -100

INPUT IMPEDANCE: 20k ohms (including
OUTPUT IMPEDANCE: 316 ohms
TONE CONTROLS> Bass: +/- 16

MAXIMUM OUTPUT: 4 volts RMS into 150 ohm load
OUTPUT IMPEDANCE: 150 ohms

kHz):

dB

dB

-

170 kHz, -3 dB, into

Treble: +/- 14

10k

ohm load

.008% @

PHONO/AUX1

dB

@ 20 Hz, moving inflection, variable turnover

dB @

20 kHz, shelving @ 5 kHz, fixed turnover

2 volts RMS

dB

when phono option not installed)

-4-

GENERALjINPUTS: Tuner, Video, CD, Phono/Aux 1, Aux 2, Tape Monitor

IEC Type 320, 3-wire, 18 gauge

INFORMATION

INSTALLATION

OUTPUTS: Out 1, Out 2, Record Out, Headphone
CONTROLS: input Selector, Volume, Tape Monitor , Tone Control In, Balance, Bass, Treble,

Output Off, Power, Phono MM/MC

INDICATORS: Mute/Standby, Power

CONVENIENCE OUTLETS: 1 Unswitched, 4 Switched (Polarized)

(Convenience Outlets are not included on 200-240 VAC units)

PHYSICAL DIMENSIONS:
17”

(W) x 7-5/8” (D) x

43.2cm (W) x 19.4cm (D) x 4.5cm (H) (excluding feet); Faceplate 43.2cm or
POWER CONSUMPTION (Excluding Convenience Outlets): 9 watts Max.

AC LINE VOLTAGE OPERATING RANGE: (exceeding lower limit will activate muting circuit;
exceeding upper limit will result in overheating and/or component damage)

100

-

120 Volt 50/80 Hz Models: 85 - 130 volts

200

-

240 Volt 50/80 Hz Models: 170 - 280 volts

l-3/4”

(H) (excluding feet); Faceplate 17” or 19” (W).

483cm

(W).

RACKMOUNTING

VENTllATlON/

PLACEMENT

LINE VOLTAGE

The 915 Preamplifier is supplied in either a 17” Black Version, or a 19” Silver Version. The 19
model has rackmounting holes provided for installation in equipment racks. The holes are on
standard EIA spacings.

The 915 produces very little heat during operation, and therefore requires no special consider­ations for ventilation. The preamplifier should be located at least several inches away from
components that contain large power transformers (such as power amplifiers), due to the
possibility of audible hum or buzz from magnetic radiation.

The 915 Preamplifier is configurable for either 100
is accomplished by changing internal jumpers on the printed circuit board. The procedure is
detailed in the section “CHANGING LINE VOLTAGE RATING”. Make sure that the unit is
configured for your local AC line voltage before attempted use. The configuration is labelled
directly above the power cord connector.

OPERATION/CONNECTIONS

POWER CORD

CONNECTION

Units wired for200-240 VACare supplied without power cords. Local agents will supply cords with

male connectors appropriate to the local standard.

Units wired for

connector plugs into the receptacle provided on the rear panel. This power cord is a standard

IEC Type 320, 3-wire, 18 gauge assembly. Should replacement ever be necessary, be sure to

replace it with an identical cord.

100-120

-

120 volt, or 200 - 240 volt operation. This

VAC are supplied with a detachable AC power cord. The female

Never remove the grounding pin from the male end of the cord.

wall outlet is not available, a ground adaptor should be employed, with the ground tab or wire of
the adaptor connected to a suitable earth ground.

INITIAL POWER-

UP/MUTING

SYSTEM

For units wired for 200-240 VAC, the front panel Power Switch controls the power to the
Preamplifier’s circuitry. If desired, this switch may be left “on” at all times to allow circuits to be

thermally stabilized for maximum fidelity as soon as the system is used.

In applications where a grounded

-5-

For units wired for

-6-

100-

120 VAC, the Power Switch controls the Switched Convenience Outlets only.
As soon as the 915 is plugged into the AC line, power is applied to the circuitry (regardless of the
position of the front panel Power Switch). Therefore, all connections should be performed with the unit

unplugged.

For all units, when power is applied, the Ready Light will glow red for several seconds, indicating that
the Audio and Headphone Outputs are muted. Once the delay period has passed and the power
supply has stabilized, the light will turn green. The preamplifier is now ready to enjoy.

The muting will reactivate immediately (and the Ready Light turn red) upon loss of AC line voltage,
(or operating the Power Switch on 200-240 VAC units), or if line voltage falls below a level which
precludes proper operation of the preamplifier’s circuitry.

CONVENIENCE

OUTLETS

Safety requirements.

The remaining four Switched Outlets are powered when the front panel Power Switch is engaged, as
indicated by the switch’s green pilot light.

The maximum power available from these outlets is 1200 watts total. This total power may be drawn
from a single outlet, or a combination of outlets. Since some power amplifiers consume more than

convenience outlets.

LINE LEVEL

INPUTS

The inputs labelled CD, Tuner, Video, Aux 2, and Phono/Aux 1 (when the Phono Option is not
installed), are identical line level inputs. The names chosen for these inputs are for convenience only,
and may be used interchangeably, or for any other type of line level source. These inputs are selected
via the rotary front panel Selector Switch.

The Phono/Aux 1 input is converted from a line level input to a high gain RIAA phono input when the

The 915 Preamplifier is available with an optional Phono Amplifier section. This option may be

will be filled by a plastic cover.

Units wired for 200-240 VAC are supplied without convenience outlets to conform to Regulatory

700-

Units wired for

720 VAC have a total of five outlets for connection of associated components. The

Unswitched Outlet is powered at all times, which should generally be used for a turntable or tape deck.

1200 watts at maximum output, check the power amplifier’s rating before connecting to these

Phono Option is installed. See Phono Section.

installed at time of purchase, or at a later date. Inclusion of this option is indicated by the presence

of a switch button protruding from the rear panel opening marked MC/MM. Otherwise, this opening

PHONO SECTION

(When Installed)

-

The MC/MM switch should be set to MC for low output (typically 0.2

-

and set to MM for high output (2

5 mV) moving coil cartridges or moving magnet cartridges.

0.5 mV) moving coil cartridges,

NEVER OPERATE THE MC/MM SWITCH UNLESS THE VOLUME CONTROL IS TURNED FULLY

DOWN. The very high gain present in the Phono Amplifier can result in switching transients capable

of blowing amplifier or speaker fuses, and possibly damaging some loudspeakers.

The ground terminal near the MC/MM switch is provided for turntable frame grounding via the extra

ground wire provided on most turntables.

As supplied from the factory, the phono cartridge input termination is 47,000 ohms in parallel with 220

pF

in the Moving Magnet mode, and 100 ohms in the Moving Coil mode. The value of capacitance
and resistance is user selectable via plug-in components. See “Installing Cartridge Loads” for further
information and instructions.

INPUT SELECTOR

0

VOLUME CONTROL BASS CONTROL

BALANCE CONTROL TREBLE CONTROL

HEADPHONE JACK

POWER SWITCH
UP TO TURN ON

SWITCHED OUTLETS*

I

-l
I

0

.

RACKMOUNT HOLES

(19”

VERSION ONLY)

w

TAPE MONITOR SWITCH

UP TO MONITOR TAPE INPUT UP TO ACTIVATE BASS & TREBLE UP TO TURN OFF RED FOR MUTE ACTIVATED

TONE IN SWITCH OUTPUT OFF SWITCH READY LIGHT

OUT1 &OUT2

GREEN FOR OPERATE

A

CJ

915 PREAMPLIFIER FRONT PANEL VIEW

*lOO-120

200-240 VAC UNITS ARE WITHOUT CONVENIENCE OUTLETS:

POWER SWITCH CONTROLS PREAMPLIFIER POWER.

VAC UNITS ONLY.

0

GROUND

PHONO CHASSIS

1

PHONO/AUX

TUNER

VIDEO CD

AUX 2

TAPE

REC OUT

OUT 2

1

OUT

MOVING MAGNET

-

MC/MM SWITCH

IN-MOVING COIL

(PHONO OPTION ONLY)

OUT

INPUTS

LEFT CHANNEL

-

RIGHT CHANNEL

-

BOTTOM ROW

TOP ROW

OUTPUTS

20 VAC UNITS ONLY.

*100-l

OUTLET*

UNSWITCHED

RATING

AC LINE VOLTAGE

SWITCHED OUTLETS

LINE CORD CONNECTOR

200-240 VAC UNITS ARE WITHOUT CONVENIENCE OUTLETS.

915 PREAMPLIFIER REAR PANEL VIEW

TAPE INPUT/

RECORD OUTPUT

The 915 incorporates one monitoring loop for use with tape decks, or other input/output signal

processors.

The

Ret

Out jack feeds a signal to a tape recorder’s input. The signal present at this output is

the same as indicated by the Selector Switch. This output may alternately be used to feed the

input of a signal processing device, such as an equalizer.

Rec

Though rare, it is possible that some external devices connected to

distortion to the main signal path when that device is turned off. This is due to possible
semiconductor junction rectification in unpowered circuits. If this is suspected, leave power

Rec

applied to any device connected to

The Tape Input is electrically the same as the other line level inputs, but is selected via the Tape

Monitor Switch. Activating this switch (UP position) breaks the main signal path after the Input
Selector System and allows monitoring of the tape decks output, during recording or playback.

Activating this switch does not affect the signal at the
The Tape Input may alternately be used for the return signal from a signal processing device, such

as an equalizer. The Tape Input may also be used for an additional line level input, although this
signal cannot be made available to the

A common system “malfunction” can often be traced to inadvertently leaving the Tape Monitor

Switch engaged: in case of no sound from a selected line level input, check that the Tape Monitor
Switch is de-activated (DOWN position).

Out during critical listening.

Rec

Out jacks.

Rec

Out jacks.

Out may cause slight

TONE CONTROLS/

TONE SWITCH

VOLUME

CONTROL

See the Functional Block Diagram for a better understanding of the Tape Monitor Signal routing.

The Tone In Switch activates the Bass and Treble Controls when moved to the UP position.
the DOWN position, the Tone Controls are completely removed from the signal path, regardless

of Bass and Treble knob position.

The Bass Control has a variable inflection, or “hinge” point so that only the very low frequencies
are affected by small amounts of knob rotation on either side of center. This facilitates small
amounts of low frequency corrections without noticeably altering the musical balance at upper

bass frequencies. As the knob rotation is increased further from center, frequencies closer to 500
Hz are affected.

kHz

The Treble Control has a fixed “hinge” point at 1
This affords proper high frequency corrections without irritation from excessive boost at extreme

high frequencies.

Activating the Tone Control Switch may cause a slight change in tonal balance even when both

Bass and Treble controls are in their center
should be disabled via the switch when no tone control action is desired. The tone controls also
limit the total

This precision
clockwise from the 12 o’clock position. Counterclockwise from the 12 o’clock position, each step

is progressively greater until full attenuation is achieved at maximum counterclockwise position.

This arrangement allows the most natural and useful volume control action for a wide variety of

listening levels.

bandpass of the line amplifier.

detented

potentiometer increases output level in approximately 1 dB steps

detented position, and therefore the Tone System

and has a “shelving” action above 5

In

kHz.

BALANCE

CONTROL

This control alters the proportion between right and left output volumes. In the full counterclockwise

position, only the left channel will be heard. In the full clockwise position, only the right channel

will be heard. The Balance Control is useful for balancing the acoustic output of the system

between left and right speakers, as well as being useful for system troubleshooting.

-9-

OUT 1, OUT 2

-lO-

AND OUTPUT OFF

SWITCH

HEADPHONE

OUTPUT

Activating this switch (UP position) turns off both Out 1 and Out 2. It does not affect the headphone
output. This control is useful for turning off the signal to the power amplifier(s) during headphone
listening, or for general system muting purposes.

When activated, the output switch disconnects the line amplifier from the output jacks, and grounds
the jacks to prevent possible system noise due to open amplifier inputs.

Out 1 and Out 2 are connected in parallel, to provide two equal outputs to amplifiers. This feature is
useful for bi-amplified speaker systems, or for running two amplifier/speaker systems.

A common system “malfunction” can often be traced to inadvertently leaving the Output Off Switch

engaged. In case of no sound from the speakers, check that the Output Switch is de-activated (DOWN
position).

1/4”

The headphone receptacle is a standard
channel, the ring the right channel, and the barrel ground.

The headphone driver circuit is separate from the main line amplifier, and therefore, driving

headphones will not cause distortion on the main outputs.
Unless simultaneously operating loudspeakers during headphone use, the Output Off Switch should

be used to disable the outputs. Remember to reduce the Volume Control setting before turning on the
outputs again, since a normal listening level for headphones may correspond to a surprisingly high

volume for loudspeakers.

stereo phone jack, with the tip of the plug as the left

CIRCUIT DESCRIPTION

PHONO SECTION

(When Installed)

Each Phono channel consists of six low-noise JFET's connected in a complementary-symmetry, non-

differential configuration. Shorted-input moving coil equivalent-input noise measures about -137 dB

(140 nV) wide band.
Only two stages are used to yield an open-RIAA-loop gain of about 110 dB in moving coil mode and

90 dB in moving magnet mode. RIAA loop closure yields 58.5 dB and 38.5 dB respectively, at 1 kHz.

The first stage employs an active load technique in which the load JFET’s are connected as gyrators,

acting as if they were very large inductors. This arrangement allows very high gain at low frequencies
and a natural roll-off of high frequencies in the amplifier loop, before the RIAA negative feedback loop
is closed.

DC operating point stability is obtained by long time constant DC negative feedback applied from
output to intermediate points in the gain structure.

AC gain is set by the RIAA network feeding back output signals to the sources of the input JFET pair.
Switching to moving coil (MC) from moving magnet (MM) results in three operational changes: 1)
open-loop gain is increased by 20 dB, 2) closed-loop gain is increased by 20 dB, and 3) user adjustable
cartridge loading is changed from capacitive to resistive.

The phono outputs are capacitively connected to the high level Input Selector System.

LINE LEVEL

INPUT SELECTOR

SYSTEM

The front panel rotary input Selector Switch creates digital codes fed to a CMOS-FET electronic

switch. This arrangement eliminates signal degradation due to mechanical switch contacts, and
allows the electronic switches to be located close to the rear panel inputs for minimum signal path
lengths and reduced interchannel crosstalk. The output of the Selector System is grounded between
positions of the rotary knob to minimize switching noise.

JFET

BUFFER AND

RECORD OUTPUT

DRIVER

The output of the Selector System is followed by a very high input-impedance JFET buffer pair
to establish negligible CMOS switch loading (for low distortion) and to provide a low-impedance
source for the Record Output and the Volume and Balance controls.

TAPE MONITOR

SWITCHING

VOLUME AND

BALANCE CONTROLS

LINE AMPLIFIER

TONE CONTROL

SYSTEM

The Tape Monitor Switch drives a relay to break the line input path to insert tape input signals.
The relay employs gold plated contacts, and allows optimum signal routing by placing the relay
close to the Tape Input jacks and the Input Selector System.

The Volume Control is a precision detented potentiometer employing laser-trimmed elements for
precise channel-balance tracking and a multi-finger wiper for smooth action, prolonged life, and
minimum contact noise. The center-detented Balance Control yields channel balance within 0.1
dB in its center position.

The 915 Line Amplifier is a Class-A JFET design employing a differential input stage, driving a
complementary high gain output stage, symmetrically driven for balanced slew-rate and low
harmonic distortion. This topology uses only four active devices per channel and extremely short
loop feedback, yielding high bandwidth and excellent stability.

The feedback loop contains two user selectable paths: one conventional path for flat response,
and another path allowing insertion of a tone control network. This arrangement allows maximally

flat response and the shortest, cleanest signal path when tone control action is not required.

The output of the Line Amplifier is capacitor coupled to the outputs of the preamplifier.
The Tone In Switch allows complete removal of the tone controls from the signal path. This

switching is accomplished with the same type of CMOS-FET electronic switch used for the Input
Selector. This switching arrangement eliminates signal degradation due to mechanical switch
contacts, and allows the electronic switch to be located very close to the Line Amplifier circuitry.

MUTING

SYSTEM

POWER SUPPLY

The Bass Control is of a moving inflection, variable turnover type, and the Treble Control is of a

shelving, variable turnover type. These types of tone controls offer the best “tools” for modifying

tonal balance without introducing unwanted side effects.
The Muting System monitors the difference between the raw (unregulated) power supply voltage

and the regulated power supply voltage. During the power-up cycle, the Audio and Headphone
Outputs are muted until the difference between the unregulated and regulated voltages reaches
a predetermined level, and then remain muted for several seconds to allow all circuitry to stabilize.
During power-down, or in cases of excessively low AC line voltage, the Audio and Headphone
Outputs are instantly muted to avoid extraneous noises.

The muting is accomplished by grounding the output of the Line Amplifier, using a relay with gold
contacts.

The printed circuit board mounted power transformer utilizes dual primaries for worldwide
operation. Internal jumpers configure the power supply for rated operation from 100 to 120 VAC,
or 200 to 240 VAC, at 50 or 60 Hz. A generous amount of power supply headroom allows actual
operation over much wider ranges of 85 to 130 VAC, or 170 to 260 VAC.

The power transformer feeds a conventional split full wave bridge rectifier system.
capacitance is 4700
provided by three-terminal heatsink-mounted regulators. Further local power supply filtering of

UF per rail is provided for each channel of the Line and Phono Amplifiers. All electrolytic filter

470

capacitors are bypassed by high quality film capacitors.

pF per rail. Stable and consistent

± l5

volt power for the amplifier circuits is

Power supply

-ll-

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.

HEADPHONE

AMPLIFIER

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.

Place the preamplifier on a soft, protective surface.

1)

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.

Remove the eight allen head screws (four

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

2)

jacks, labelled RJ5, RJ7, and RJ8. Remove the three jumper wires as shown. These jumpers

may be de-soldered or clipped out.
Refer to the diagram “Installation Of Optional Phono Printed Circuit Board”. Push the MC/MM

3)

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.
Add the button to the shaft of the MC/MM switch. Unless modifying the cartridge loads at this

4)

time, replace the covers. (See Installing Cartridge Loads).

-12-

-T

PLASTIC BUTTON

PHONO PC BOARD

MAIN PC BOARD

4 PIN CONNECTORS

PLASTIC STANDOFFS

INSTALLATION OF OPTIONAL PHONO PRINTED CIRCUIT BOARD

INSTALLING

Resistors

Capacitors

100 ohm resistors

220

CARTRIDGE LOADS

Optional cartridge loading is a “fine tuning” matter. Many cartridges are not sensitive to loading
and work well without it. Only a cartridge’s manufacturer can provide recommended loading, as
every cartridge is different. And only the user can say for sure whether or not it produces
meaningful sonic improvement.

Components suitable for cartridge loads may be obtained from electronic parts or specialty audio

l/4

component suppliers. Resistors should be 1% tolerance, metal-film,

watt types. Capacitors

should be axial lead, 10% (or better) tolerance, miniature polypropylene or polystyrene types.
As supplied from the factory, the 915 Preamplifier has been fitted with 100 ohm resistors and 220

pF capacitors installed in the appropriate sockets. While these values are suitable for most
cartridges, the procedure described below may be used to alter these values. Review the
installation instructions before attempting this procedure. If any doubts exist about one’s ability
to install the cartridge loads, it is advisable that the procedure be conducted by a qualified
technician.

CHANGING UNE

VOLTAGE RATlNG

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 four allen head screws (two

on each side), and three phillips head screws, securing the bottom cover. Remove cover.

2)

Refer to the diagram “Installation Of Optional Cartridge Loads” for the location of the
appropriate sockets, and how to form the component leads. Make sure that the component
leads are only long enough to securely mate to the sockets. Be sure not to stress the
component lead where it enters the body of the part. Observe carefully which sockets are
for MM (capacitors) and for MC (resistors).

3) Replace cover.

NOTE:

Even while experimenting with different optional loads, the cover must be replaced before
re-applying AC power, not only for safety reasons, but to shield hum and interference which can
totally invalidate any attempts at sonic evaluation.

CAUTION:

When low value resistors are installed and selected by the MC switch position,
accidentally using this setup for a high output moving coil cartridge can result in deceptively normal
output levels, but with improper cartridge frequency response.

-

The 915 Preamplifier can be internally wired for two different AC line voltage ranges: 100

-

VAC, or 200

240 VAC, 50/60 Hz. The configuration is labelled above the power cord connector.

120

If the preamplifier will be used in a location that requires a different line voltage, it is possible to

change the configuration. Review the modification instructions before attempting this procedure.

If any doubts exist about one’s ability to change the line voltage, it is advisable that the procedure

be conducted by a qualified technician.

NOTE:

As supplied from the factory, units wired for 100-l 20 VAC have five Convenience Outlets,
and the Power Switch controls the Switched Convenience Outlets only. (Power is applied to the
preamplifier’s circuitry as soon as the unit is plugged in.) For units factory wired for 200-240 VAC,

no Convenience Outlets are supplied, and the Power Switch controls application of power to the

preamplifier’s circuitry. Note that changing the Line Voltage affects only the operating line voltage:
the above described switching arrangements will remain the same.

WARNING!

UNPLUG THE UNIT FROM AC POWER BEFORE ATTEMPTING THIS PROCE-

DURE. FAILURE TO DO SO CAN RESULT IN SEVERE ELECTRICAL SHOCK.

-14-

MAX.

3181'3181'

PHONO LOAD SOCKETS

DETAIL OF COMPONENT INSERTION INTO

(INSERT LEADS INTO OUTER TWO HOLES)

\

(CAPACITORS)

MOVING MAGNET LOADS

1

(RESISTORS)

MOVING COIL LOADS

-

PHONO BOARD

INSTALLATION OF OPTIONAL CARTRIDGE LOADS

Place the preamplifier on a soft, protective surface. Remove the eight allen head screws (four

-16-

on each side), and six phillips head screws (three each on top and bottom), securing the top and
bottom covers. Remove covers.

Referring to the diagram “Main Printed Circuit Board Component Layout”, locate the three wire

2)

jumper locations labelled “A”, “B”, and "C", in front of the power transformer. These jumpers

control the series/parallel connections of the power transformer’s primary.
Remove the old jumper(s) by desoldering and replace with new jumper(s) as indicated:

3)
100 - 120 VAC: Jumpers A & B installed

-

240 VAC: Jumper C installed

200
Be sure to clip off excess wire length on the solder (non-component) side of the printed circuit

board.
Referring again to the diagram, locate the clip-mounted fuse. Replace this fuse with a new slow-

4)

blow fuse as indicated:

-

120 VAC:

100

-

240 VAC: 1 /16 AMP

200
Referring again to the diagram, locate the wire jumper location labelled “Remove For 240

5)

1/10

AMP

VAC”, behind the transformer. This jumper controls the voltage supplied to the Power Switch
indicator lamp. Remove or install this jumper as indicated:

-

120 VAC: Jumper Installed

100

-

240 VAC: Jumper Removed

200

GENERAL

TROUBLESHOOTING

HINTS

Replace the covers.

6)

Obtain a new voltage configuration label from the factory, and affix over the original markings.

7)

Alternately, prepare a small self adhesive label and indicate the new voltage range with
permanent ink. Relabelling the unit is a vital safety requirement, particularly if the preamplifier
is sold to a new owner.

The 915 Preamplifier is configured for normal operation when all toggle switches are in the “down”
position. That is, Tape Monitor is NOT selected, Tone Controls are OFF, and the outputs are ON. If

no sound is heard from the system, first check the position of the Tape Monitor and Output switches.
If altered tonal balance is detected (even with the Bass and Treble controls centered), check the

position of the Tone switch.

If the Ready light is off or glowing red, the preamplifier’s outputs are muted and no sound will be heard.
If rated AC power is present and the light is glowing red, then the delay circuit will un-mute the outputs

within several seconds. If the delay circuit does not un-mute within a few seconds and the light
continues to glow red, check for low AC line voltage, and that the unit is configured for the local line
voltage. If the Ready light is off, check the AC power connections.

If all controls are in the intended position and the Ready light is green, check all system power

connections, interconnecting and speaker cables, and fuses. The 915 does contain one internal

power fuse, but this fuse should not generally blow unless a malfunction has occurred. This fuse

should be replaced only with the exact type and rating of fuse originally supplied. If this fuse is replaced
and blows again within a short time, disconnect all power immediately and return for service.

If all controls, fuses, cables, etc. seem to be functioning properly, a process of one-at-a-time

component substitution should be employed until the defective unit is identified. If only one channel

is not functioning properly, a one-at-a-time reversal of interconnect and speaker cables from left to
right should reveal the malfunctioning component.

GROUND

LOOPS

Ground loops are characterized by a low level hum or buzz in the system. Loops are caused by
a voltage potential difference between two points in a ground circuit, and aggravated when multiple
paths for a given circuit exist. Noise-free audio performance is dependent upon all grounds being
at the same potential, with a single path for each ground connection. Ground loops can exist in

two forms: 1) loops created in audio interconnects, and 2) loops created between earth grounded

chassis.
Mounting components to a rack with metallic rails may introduce ground loops between associated

equipment, because the rails can introduce a second ground path. The extent of this problem will
depend on the grounding arrangements of associated equipment. Ground loops can occur in non­rackmounted equipment, though it is less common.

If ground loops occur, and any other component in the system has a three wire grounded power
cord, the first step should be to use a ground adaptor (with the ground tab or wire of the adaptor
not connected) on the power cord plug of the preamplifier. DO NOT cut off the grounding pin on
the plug! It may be necessary to use additional adaptors on other grounded components if more
than two components are earth grounded. (In other words, only one earth ground per system
should exist.) Another potential source of multiple earth grounds is from coaxial antenna or cable
service feeds for FM or video sources, which usually are (and should be) earth grounded. The
ground adaptor(s) should cure this grounding problem as well.

WARNING: The use of ground adaptors (with the ground tab or wire of the adaptor
disconnected) will eliminate the safety feature of the grounded power cord. This safety
feature is intended to reduce the risk of electric shock should an internal fault in the
equipment result in an electrically “live” chassis. Therefore, this method of ground
isolation should be employed only when absolutely necessary, rather than as a general
practice. When using a ground adaptor for isolation, make sure that the power cord plug
is inserted into the receptacle in the same orientation as if no adaptor were present, to
maintain the same hot/neutral polarity.

CLEANING/

MAINTENANCE

SPECIAL NOTE ON VIDEO CABLE “GROUNDS”:

of cable service and antenna feeds should be connected to earth ground. Often, however, due
to long feed lengths, especially in apartment distribution systems, this ground will be of poor quality
and could be a source of noise. This interference is usually characterized by a high frequency
noise, rather than a hum or a buzz. If such interference is experienced, a separate earth ground
connection should be made from the cable outlet nearest the audio/video equipment to a known
good earth ground.

If ground loops exist due to potential differences in the interconnects in rack mounted systems,
then it is advisable to isolate the preamplifier chassis from the rack rails. This may be
accomplished by sandwiching a thin sheet of insulating material (i.e., plastic washers or several

layers of electrical tape, etc.) between the rack and the preamplifier, and securing the unit with non­metallic (i.e., nylon, etc.) hardware. It may be necessary to insulate other components so that only
one component is directly connected to the rack rails.

If the faceplate should become soiled, it may be cleaned with a slightly damp, soft cloth, and, if

necessary, a mild detergent. Do not use any abrasive cleaners or solvents. Unplug the power cord

before attempting any cleaning operations.

Except as specifically detailed in the owners manual, there are no user serviceable parts or

adjustments inside the 915 Preamplifier, and all servicing should be referred to qualified,
authorized personnel. The only user access to the inside of the chassis should be for changing
the optional loading for the phono inputs (when installed). See “Phono Section”.

As mentioned above, the ground conductor

-17-

ONE CHANNEL SHOWN, PHONO OPTION INSTALLED

915 PREAMPLIFIER FUNCTIONAL BLOCK DIAGRAM

I

I

t

PARTS LIST - MAIN CIRCUIT BOARD

PARTS LIST

DESIGNATORS l-99: FOR COMMON AND RIGHT CHANNEL PARTS 100-199: FOR LEFT CHANNEL

DESIGNATOR VALUE

ALL RESISTORS
R1, R101
R2, R102
R3
R4
R5
R6, R106
R7, R107
R8, R106
R9, R109
R10, R110
R11, R111
R12
R13, R113
R14
R15, R115
R16, R116
R17, R117
R16, R116
R19
R20
R21
R22
R23
R24
R25
R26
R27
R26
R29, R129
R30, R130
R31, R131
R32, R132
R33, R133
R34, R134
R35, R135
R36, R136
R37, R137
R36, R136
R39, R139
R40, R140
R41, R141
R42, R142
R43, R143
R44, R144
R45, R145
R46, R146
R47. R147
R46, R146
R49, R149
R50, R150
R51, R151
R52
R53

DIODES

D1
D2

D3
D4
D5
D6
D7
D6
D9
D10
D11
D12
D13
D14
D15

1/4

WATT, 1% METAL FILM

2.15K
20K

100K
100K
100K

20K

1K
1K

33.2

33.2
20K
221
20K
100K

182K
100K

150

274K

10K
162K
100K
100K

4.75K

47.5K

1.5K

2.21K
150K
1K

499

11K

1.1K
11K
11K
11K

1.1K

1.1K

316
316
20K
316

100
100

4.99K
10K

4.7M

20K

1

.0M
100
100
100K

316

10K
10K

1N4003
1N5239B
1N5239B
1N4003
1N4736A 6.8V
1N4148
1N5226B
1N4003
1N4003
1N4148
1N4148
1N4148
1N4148
1N4003
1N4003

9.1V

9.1V

3.3V

PART NUMBER

RMP/4-2151
RMP/4-2002
RMP/4-1003
RMP/4-1003
RMP/4-1003
RMP/4-2002
RMP/4-1001
RMP/4-1001
RMP/4-0332
RMP/4-0332
RMP/4-2092
RMP/4-2210
RMP/4-2002
RMP/4-1003
RMP/4-1623
RMP/4-1003
RMP/4-1500
RMP/4-2743
RMP/4-1002
RMP/4-1623
RMP/4-1003
RMP/4-1003
RMP/4-4751
RMP/4-4752
RMP/4-1501
RMP/4-2211
RMP/4-1503
RMP/4-1001
RMP14-4990
RMP/4-1102
RMP/4-1101
RMP/4-1102
RMP/4-1102
RMP/4-1102
RMP/4-1101
RMP/4-1101
RMP/4-3160
RMP/l4-3160
RMP/4-2002
RMP/4-3160
RMP/4-1000
RMP/4-1000
RMP/4-4991
RMP/4-1002
RMP/4-4754
RMP/4-2002
RMP/4-1004
RMP/4-1000
RMP/4-1000
RMP/4-1003
RMP/4-3160
RMP/4-1002
RMP/4-1002

SS-161
SSH-652
SSH-652
SS-161
ss-171
SS-162
SSH-653
SS-161
SS-161
SS-162
SS-162
SS-162
SS-162
SS-161
SS-161

DESIGNATOR VALUE

U1 U101 4051
U2 4053

U3 NE5532
U4 7815
U5 7915

Q1,Q101
Q2,Q102
Q3,Q103
Q4,Q104
Q5, Q105
Q6,Q106
Q7
Q8

::0

SW1
SW2

SW3
SW4

SW5, SW1 05 Toggle Switch

RLY1
RLY2

VR1, VR101
VR2, VR102
VR3, VR103
VR4, VR104

LED1 Tri-Color LED
J1-J3

J4
J5-J9

J10

F1

F1 (EXPORT)
T1
BR1
All Capacitors In Microfarads Unless Specified Otherwise

C1
C2
C3
C4
C5
C6
C7
C8
C9,C109
C10, C110
C11,C111
C12,C112
C13,C113
C14,C114
C15
C16.

C116
C17
C18, C118
C19, C119
C20, C120
C21, 121C121

C22, C122
C23, C123
C24, C124
C25, C125
C26
C27
C28
C29

2SK163, Graded
2SK163. Graded

2SK163
2SK163

2SK163
2SJ74
BC560C
BC560C
BC560C
BC550C
Rotary Switch
Toggle Switch
Toggle Switch
Power Switch

Relay
Relay

Volume Control
Balance Control
Bass Control
Treble Control

4-Pin Header
IEC Connector
Convenience Outlet
Headphone Jack

1110 Amp Slow Fuse
1 /1 6 Amp Slow Fuse

Transformer
Bridge Rectifier

4.7 25V Tant.

4.7 25V Tant.
.O1

1 KV Ceramic Disc

0.11 OOV Pofycarbonate

0.11 WV Polycarbonate

4700 35V Electrolytic
4700 35V Electrolytic

.01

Ceramic Disc, UL
.015 160V Polycarbonate
.0015 160V Polypropylene
.47 63V Polycarbonate
.047 63V Polycarbonate

470 Non Polar Electrolytic

0.1 100V Polypropylene

4.7 25V Tant.
47p Polystyrene

4.7 25V Tant.

0.1 1 OOV Polypropylene
68p

Polystyrene
470 25V Electrolytic
470 25V Electrolytic

0.1 1 WV Polypropylene

0.1 1 OOV Polypropylene

2.2 250V Polypropylene

.47

63V

PoLycarbonate
47 25V Electrolytic
470 25V Electrolytic
470 25V Electrolytic

.01

1KV Ceramic Disc

0.1 1 OOV Pofycarbonate

-19-

PART NUMBER

SSH-656
SSH-657
SSH-667
SSH-625
SSH-628

SSH-614T
SSH-614T
SSH-614
SSH-614
SSH-614
SSH-617D
SSH-651
SSH-651
SSH-651
SSH-650
SWH-153
SWH-151
SWH-151
SWH-152G (Gray)
SWH-152B (Black)
SWH-151

SWH-146
SWH-146

RVH-503C
RVH-104A
RVH-104B

RVH-1048
SSH-739
CCH-203

CCH-233
CCH-150
CCH-208

FS-111 OSB

FS-1/16SB
l-r-915
ss-222

CTR-475A

CTR-475A
CD-103/20
CPC-104
CPC-104
CER-478B

CER-478B
CD-103A

CPC-153
CPP-152
CPC-474
CPC-473
CERNP-477
CPP-104MC
CTR-475A
CPS-470
CTR-475A

CPP-104MC
CPS-680
CER-477A
CER-477A
CPP-104MC
CPP-104MC
CPP-225MC

CPC-474
CER-476A
CER-477A
CER-477A
CD-1

3/20

CPC-104

1

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10

us

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CY,.tl”P r 21”nqy

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LIOA

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lN3NOdW03

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NIVW

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-----

-1

i

+---

-L

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PWNOOPllONJUMPERS

’

A&B=100-12OVW:

c - 200-240

.di

PHONOPWER

1

+15V

VAE:

1

N5226B

D7

RlQ
1OK

+15V-

Bci

D6

lN4145

1

i

4

K

hL

Rl

-15V

CH

+15V

L CH

MUTE

RUAY

Rlb
274K

JlO

R17

BOARD CIRCUIT SCHEMATIC

ENANCE

UNLESS SPECIFIED OTHERWISE

1. RIGHT CHANNEL ONLY

2.

COMPONENT DESIGNATORS 1-99 FOR

RIGHT CHANNEL

5. ML RESISTORS IN

4.TCNE5WllCHSHWNINBYPASSPO5RlCN

5. TAPE

6.MUERW.AY5lUWNINUNMUTEDPDSnlDN

MONITOR SWITCH

SHOWN

COMMON AND

PARTS. 100-199 FUR

OHMS, CAPACITORS

SHOWN IN WE

LEFT

IN

POSITION

CHANNEL

MICROFARADS

PARTS LIST - PHONO BOARD

PARTS LIST

DESIGNATORS

DESIGNATOR VALUE
PART NUMBER

All Resistors

R1, R101
R2,

R102

R3,

R103 33.2 Low Noise
R104 681

R4,
R5, R105
R6, R106 332K
R7,

R107 47.5K

R108

R8,

R109 100

R9,

R110

R10,
R11, R111
R12,

R112
R13, R113 22.1M
R14.

R114 10M

R115 316

R15,
R16,

R116 3.32M

R117

R17,
R18,

R118

R119 10M

R19,
R20, R120 316

1-

99: FOR RIGHT CHANNEL PARTS

100-l 99: FOR LEFT CHANNEL

1/4

Watt, 1% Metal Film

681

33.2 Low Noise

26.7K

316

33.2 Low Noise

3.32M
1 .OK

1 .OK

22.1M

RMP/4-6810
RMP/8-0332LN
RMP/8-0332LN
RMP/4-6810
RMP/4-2672
RMP/4-3323
RMP/4-4752
RMP/4-3160
RMP/4-1000
RMP/8-0332LN
RMP/4-3324
RMP/4-1001
RMP/4-2215
RMP/4-1005
RMP/4-3160
RMP/4-3324
RMP/4-1001
RMP/4-2215
RMP/4-1005
RMP/4-3160

Q1, Q101
Q2,

Q102

Q3, Q103

Q104 2SJ72

Q4,
Q5,

Q105
Q106

Q6,
SW1 , SW1 01 4PDT Switch
J1-J3
All Capacitors In Microfarads Unless Specified Otherwise.
C3

C4
C5, C105
C6, C106
C7, C107
C8, C108
C9, C109

C10, C110

2SK147
2SK147
2SJ72

2SJ74
2SK163

4-Pin Receptacle

0.1 1 OOV Polypropylene

0.1 1 OOV Polypropylene

1% Polystyrene

.0027
.01

1% Polystyrene

2.2 Polyester

2.2 Polyester

2.2 250V Polypropylene

220pf Polystrene

SSH-674
SSH-674
SSH-617C
SSH-617C
SSH-617D
SSH-614

SWH-125

CCH-240

CPP-104MC
CPP-104MC
CPS-272
CPS-103
CP-225
CP-225
CPP-225MC
CPS-221

-22-

l-l

I

I I

11

44

R3nR3n

RlORlO 4-k4-k

R2 R2

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aa

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Rl9Rl9

R6 R6

EnEn

f;oRllf;oRll

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Rl4Rl4

01040104

Rl18 Rl18 "OS"OS

Rfli

Rl150Rl150 BfWOd'BfWOd'

Rll9Rll9

-fxb-fxb

33

R108R108

R103 R103

RllORllO <<

R102 R102

ii::ii::

Rl13 Rl13

00

>>

Rl14Rl14

11

[I[I

44

J3J3

5252

44

PHONO BOARD COMPONENT LAYOUT DIAGRAM

-23-

PHONO INPUT

R15

316

L CH

IMC/MM SWrrCH

PHONO

POWER

1. RIGHT CHANNEL ONLY SHOWN.

I

RlO

a2

D,‘)

,

I.,#.

1Mp

=

1 .OK

Rl

RR1

-.

I

+

II
I,

B

R18

22.1M

-%+

f

05

2sJ74

06
2SK163

R20

316

Q

J2

PHONO OUTPUT

2. COMPONENT DESIGNATORS 1-99 FOR RIGHT CHANNEL PARTS. 1 W-199 FOR LEFT CHANNEL.

3. ALL RESISTORS IN OHMS, CAPACITORS IN MICROFARADS.

4. MC/MM SWITCH SHOWN IN MOVING MAGNET POSITION.

PHONO BOARD CIRCUIT SCHEMATIC DIAGRAM

SERVICE POLICY AND LIMITED WARRANTY

If you encounter any difficulty or have any question concerning your 915 Preamplifier, please call

our Customer Service Department weekdays, 8 am to

967-3565.

Should you have any doubts as to whether the preamplifier is malfunctioning and requires
service, please call us before sending in for repair.
warranty status) must receive a Return Authorization (RA) number. In addition, we can offer
troubleshooting assistance that may simplify or even eliminate the need for factory service.

The Hafler 915 Preamplifier is warranted to the original owner (non-transferrable) for seven years
from the date of purchase, including parts, labor, and return shipping costs within the Continental
United States. This warranty applies only to products sold in the United States Of America. For
warranties outside the USA, please contact your local agent.

It is the owner’s responsibility to pay shipping (preferably United Parcel Service, UPS) to the

factory: collect shipments will not be accepted. Units under warranty should be accompanied by

a copy of the dated Bill Of Sale. Use the original carton and all packing material, with the RA
number clearly marked on the outside of the package. Be sure to include a return address, the
RA number, a daytime telephone number, and a brief description of the difficulty, including
whether it occurs continuously or intermittently.

This warranty gives you specific legal rights. You may also have other rights which vary from state
to state.

3:30

pm, Mountain Standard Time, at 602-

All units being returned (regardless of

-25-