Hafler DH 120 Service Manual

Page 1

THE

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POWER AMPLIFIER

INSTRUCTIONS
for OPERATION
and KIT ASSEMBLY

NOTE:

, » 7 . IF THE. SPEAKER FUSES BLOW. NO SOUND
gr , WILL BE HEARD. ALWAYS CHECK FOR
BLOWN FUSES FIRST.

LM 124 Please reler Io this
serial number in all communications
$3.00 regarding (his equipment

THE DAVID HAFLER COMPANY A
5910 Crescent Boulevard, Pennsauken, New Jersey 08109

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Page 2

SPECIFICATIONS

Power Rating:

Less than 0.009% total harmonic distortion at any power
level up to 60 watts continuous average power per
channel into 8 ohms at any frequency between 20 Hz and
20 kHz with both channels driven.

[M Distortion (SMPTE):
Less than 0.005% from 1 watt to 60 watts, each
channel, into 8 ohms.

Typical THD at 60 watts into 8 ohms:

20 HZ: 0.002%
1 kz: 0.002%
20 kHz: 0.006%

Frequency Response into 8 ohms:

- 3 db, 4 Hz to 200 kHz at 1 watt.

+0 db, A05 db, 10 Hz to 40 kHz at 60 watts.
Typical Channel Separation:

20 Hz: > 75 db
l kHz: > 85 db

20 kHz: > 65 db
Signal to Noise Ratio, unweighted:

Exceeds 100 db referred to 60 watts into 8 ohms.
Input Impedance:

22,000 ohms.
Input Sensitivity:

1.1 volts ms for 60 watts into 8 ohms.
Damping Factor:

[00 to 1 kHz into 8 ohms

50 to 10 kHz into 8 ohms
Rise Time:

10 kHz, 45 volts peak to peak square wave, 10% to

90%: 2 us.
Slew Rate:

10 kHz, 45 volts peak to peak square wave: 30V/us.

Semiconductor Complement:

22 Transistors, 4 Power MOSFETs, 23 Diodes, 8
Zener Diodes, l Diode Bridge.

Power Consumption:

60 watts both channels into 8 ohms: 300 VA
Quiescent: 60 VA

Size:
3-1/4 high plus 1/2" feet, 15-3/4 wide, 9 deep.

Net Weight:
18 lbs.

Shipping Weight:
20 lbs.

All specifications are subject to change without notice.

© Copyright 1985. All rights reserved.

INTRODUCTION

The Hafler DH-l20 is a two channel medium power audio
amplifier which has been engineered to the very highest
performance standards. With conservative design and
commensurate reliability, it follows in the Hafler tradition of
exceptional value. Plus, its availability as an easily completed
kit with specifications identical to those which are factory built,
provides additional savings for a few hours time.

As a direct descendant of the DH-220 amplifier, the DH»120
employs the latest MOSFET technology with all silicon devices
in a direct coupled configuration (except at the input). With its
own unique circuit, the DH-lZO utilizes the latest circuit
topology and capacitor interfacing for superior sound quality in
either stereo, or in the bridged mono mode. The MOSFET
output devices provide exceptional reliability and resistance to
abusive operating conditions, and avoid the need for special
protective circuits which compromise audio performance. Their
ruggedness and self-protective capability enables the DH- 1 20 to
deliver very high currents into very low impedances - even
into a short circuit 7 affording audible benefits when driving
difficult loudspeaker loads. This unique Hafler design gives you
the three primary benefits: circuit simplicity, added reliability,
and better sound, all at reasonable costr

This design includes basic protective systems to provide
maximum security against malfunction damage to either the
amplifier or to the speaker: an AC line fuse, B + and B- fuses
and thermal breakers on each channel, and fuses to protect the
loudspeakers. Only the loudspeaker fuses are accessible on the
back panel, since these should be chosen with the loudspeakers
power limits in mind. When they are appropriately sized to
protect the speakers, they may blow on occasion. Thus it is
advisable to keep replacements on hand. However, the failure of
an internal fuse should be cause for a complete inspection by a
competent technician.

An exclusive adjunct in this design is the provision for
connecting a second set of loudspeakers in such a way that they
can reproduce the ambience information which is not accessible
with a single pair of stereo loudspeakers. Many disc and video
recordings, and most live broadcasts include reverberant audio
information which can provide a sense of the surrounding space,
yet this is not perceived with two speaker reproduction. The
Hafler Ambience Recovery System will not interfere with the
customary stereo sound reproduction, but it can provide added
realism and pleasure to users who have a second pair of speakers
available for this use.

Those who use these instructions to assemble the DH-IZO kit
will find that the left and right audio modules (printed circuit
and heat sink assemblies) are fully assembled. This greatly
simplifies the completion of the kit, so it can be done in a few
hours without special skills. It also assures the audio integrity of
the finished product, since all the active circuitry has been tested
to meet specified performance criteria which are the same as for
factory assembled amplifiers. This modular design also makes it
possible to operate only one channel if the other requires
service, and avoids the need to retum the entire heavy amplifier
when only one channel is at fault.

Accessories for special applications include a panel to
facilitate standard 19" rack mounting, and an alternative power
transformer to accomodate international AC line voltages.

Welcome to Hafler affordable high technology high fidelity!