Hafler DH 102 Service Manual

Page 1

Operating and Installation Instructions for
THE HAFLER DH-102 PRE-PREAMPLIFIER.

Moving coil phonograph cartridges have extremely low output

levels, and thus require more gain than the standard phono
preamplifier can provide. A pre-preamplifier, or head amplifier, is
thus required. To preserve the subtle sonic benefits of which mov-
ing coil designs are capable demands not only low noise. but stan»
dards of low distortion, low phase shift, and accurate transient
response commensurate with the very finest preamplifiers.

The DH-lOZ is a discrete transistor design which is a direct out-
growth of the fully complementary mirror-image circuitry which
has earned for the DH-l 01 control preamplifier the accolades of so
many reviewers whose listening judgement is widely regarded. The
DH-l02 installs inside the DH-lOl , and converts the Phone 2 in-
put to moving coil suitability. It boasts exceptional signal handling
capabilities outside, as well as within the audio band, with un-
measureable levels of ultra-sonic intermodulation distortion
(USlM). High frequency high level signals, where record pre-
emphasis makes the task the hardest, are handled with exceptional
ease. The DH-lOZ has a 500% safety margin at 20 kHz iwhere the
demands are greatest, and 10 times that in the mid-band, where the
requirements are more modest. Pulse tests and the reproduction of
high frequency RlAA preemphasized square Waves confirm its
superior transient response capability.

Each DH-lO2 is fully assembled and individually tested to
assure its performance meets the high standards indicated by the
specifications. The heavy steel case provides exemplary shielding
from magnetic fields. To maintain its low noise level, 'the DH-IOZ

z-is not selfvpowered, but instead draws power from the main

camp's supply. To accommodate this, the DH«l 0] power supply

was deliberately designed with sufficient filtering and adequate

reserve. A special muting circuit in the DH-102 minimizes turn-on

transients. To provide for past, present and future moving coil

designs, an externally accessible switch provides either 20 or 34 dB
of gain. It is located on the bottom of the DH~l0L

OPERATION

Plug the output cables from a turntable which uses a moving
coil cartridge into the Phono 2 input. The output cables from con-
ventional magnetic cartridges should be connected to Phone 1. if
you interchange these canridge types in the tone arm, remember to
shift the cable connections to the appropriate input.

The pre-preamplifier provides a maximum gain of 34 dB when
the switch is toward its outer edge, or toward the nearer left side of
the bottom of the preamp, when it is installed in the DH-lOl. 20
dB of gain is provided in the other switch position. Choose the one
which suits your cartridge best, in terms of normal operation of the
preamp volume control. It is suggested that the lower gain position
be used in most instances, enabling the volume control to be oper-
ated in the upper part of its range where interchannel balance is
more closely controlled. Also, the overall signal-to-noise ratio of
the system will be highest if the preamp volume control is operated
at higher settings. Using the highvgain position when it is not
necessary will not overload the pre-preamp, but nothing is
achieved, since the noise level is proportional to the gain.

The input load impedance of the DH-l 02 is 600 ohms, which is
suitable for most moving coil cartridges. if a lower load impedance
is recommended for your cartridge, an appropriate value resistor

fimay be connected in parallel across each channel input jack on the
WH-lOl. For instance, a 120 ohm resistor across the input will
,ield an overall load of 100 ohms.

Since the DH-l02 draws its power from the low voltage sec-
ondary side of the preamp power supply, there is no concern with
differing line voltages in various countries. That has been taken
care of in the preamp power supply wiring.

SERVICE AND LIMITED WARRANTY

The DH-l 02 is warranted for a full year from the purchase date
against defects in material and workmanship. This includes pans,
labor and return shipment from the factory to the owner within the
continental U.S.A. The owner is responsible for returning the unit
to the factory, and must submit a copy of the original dated bill of
sale. Ship prepaid, preferably via United Parcel Service, and be
sure to include your return shipping street address (preferably not
a Post Office Box number),

If the DH-l02 is installed in a DH-lOl which is returned for
service, both units will be serviced under the terms and charges of
the DH-lOl warranty.

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

INSTALLATION IN THE DH-lOl
CONTROL PREAMPLIFIER

The step by step instructions detail normal installation inside
the DH-lOl, which will take less than an hour. The usual kit-
building tools are needed: 60/40 ROSIN CORE solder, a small tip
soldering iron, wire cutters and strippers, screwdriver and narrow-
nose pliers. The only skill required is knowing how to make a good
solder connection in electronic equipment. Your DH covers this in detail. If you did not build your DH-lO] from a kit,
and a review of these instructions makes you doubt installing it
yourself, your dealer or alocal Serviceman can cgmpletemc task
for a modest fee.

These instructions retain the Phone l input for conventional
magnetic cartridges, and convert only the Phone 2 position for
moving coil use.

Although the DH<102 could be used with other preamplifiers
which can provide the necessary power, the David Hafler Com-
pany cannot be responsible for the proper operation or perfor-
mance of such non-standard combinations, other than to warrant
the integrity of the DH~102 atone. All such alternative use is at the
customers risk.

INSTALLATION INSTRUCTIONS FOR THE DH-IOI

The wire colors given in parentheses ( ) conform to the
diagram for kitvbuilt DH-lOl preamplifiers, which use only red,
green and black wires This diagram, partially reproduced here in
lighter tones, with the new wiring shown full weight. represents red
wires as white, green as grey, and black as a solid tone.

if yours is a factoryassembled preamplifier, the wire colors will
be different. Just be certain that you follow the connection loca-
tions exactly.

SPECIFICATIONS

Rated Output: 300mV
THD at Rated Output: less than 0.005%
Maxi-um Output@ 0.1% THD: More than 3 V rms
Frequency Response(- 3 dB poiuu):2 Hz-l MHz
Gain (switch selected): 34 dB or 20 dB
Input Impetknce: 600 ohms in parallel with .01 [if
Output lmpethnce: 50 ohms
Minimum Load Impedance: 10K ohms
Slew Rate: 40 Was
Rise Time(10%-90%): 300 ns
Typical Equivalent Input Noise, shorted input,

20 -20 Kill: l 15 nV

A weighted: 85 nV
Power Requirements: :l: l8 VDC, 30 ma
Sin; 6.5" x 2.5" x15"
Net Weight: 30 ounces (0.9 kg.)

Page 2

Unplug the pmmps AC power cord from the wall
socket! Remove the four side screws that secure the cover.
and set these aside. Observe the (green) and (red) wires that
connect input sockets 9 and 20 to eyelets 9L and 9R on the
main circuit board. Check to see that there is sufficient
clearance for the pro-preamplifier under this pair by tem-
porarily placing it behind the main board. with the switch
handle projecting through the left side mounting hole. If
necessary, replace these wires with a longer twisted pair.
0n early production preamps. these wires were grouped
under the plastic ties alongside the braw. If yours are thus.
unsolder them at the input sockets, and pull them out of
the tics. These wires should be twisted together, shortened
as necessary. and reconnected directly to the input sockets,
leaving enough room for the pre-preamplifier to fit under-
neath. Be sure the #9 socket is connected to eyelet #9L in
the corner of the board.

2 El Remove the six screws securing the bottom plate. and set
these parts aside. Remove the U" shaped links from the
External Patch sockets, if these were installed.

3 E1 Unsolder the (red) wire from input socket #13, and un~

solder it at the other end also, where it is connected to lug

#13 of the Phono 2 switch SB. This wire will no longer be

uwd. You may choose to unwind it from the twisted group

of three. or you can simply cut it off at each end of the
group. Make sure that the bare tip cannot contact any cir-
cuitry. or the chassis or bottom.

Unsoldcr the (green) wire from input socket #2, and also

unsolder it at the other end, where it is connected to lug #1

of Phono 2 switch SB. This wire. no longer needed. may

also be removed or cut, so it cannot make any contact.

There are two short bare wire jumpers on the input socket

strips. One connects the short lugs of sockets #1 and #2.

and the other connects the short lugs of sockets #12 and

#13. Remove both of these short wires.

6 Cl Trim the DH-102 leads as follows, and bare 1/4" on each:

Right input twisted pair - 3

Left input twisted pair - 4"

Brown and Violet leads - 3"

Orange lead - 7"

Blue lead - 6-1/2"

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Black Ind - 4"
Red lead - 4-1/2"
Green lead - 5"

When installing the DH-102 in the open preamp chassis, do not
allow its weight to strain connections that have been soldered.
Since it is necessary to have both the top and bottom of the unit ac~
wssible for soldering. the DH-102 has to "float" for the present,
although it will later be fastened to the bottom plate.

7 U Place the DH-102 inside the chassis on its narrow side. so
that the switch is at the left. projecting forward. Be sure the
(red) and (green) wires to input sockets 9 and 20 are above
the DH-102. Feed the black, red and green power supply
wires through the grommet in the preamp brace. The black
wire, which will later require careful positioning, should be
inserted first. and kept towards the front and bottom of the
preamp as it coma through the grommet. If you have
difficulty getting these wires through, a bit of soap on them
will make the job easier.

Place the DH-102 against the back of the large circuit

board to give you room for soldering. Select the red and

black twisted right input pair, and solder the black wire to

the short lug between input sockets #12 and #13. Solder

the red wire to socket #13.

9 1:) Select the green and black twisted left input pair. and
solder the black wire to the short lug between input sockets
#1 and #2. Solder the green wire to socket #2.

10 Cl Select the brown wire and solder it to input socket #21. A
(grwn) wire is already connected to this socket. Be sure
both wires are soldered.

8C1

moans haflemm

5910 Crescent Boulevard. Pennsauken. New Jersey 08109

1 1 D Select the violet wire and solder it to input socket #10. Be
sure both it and the existing (red) wire are soldered.

12 El Select the blue wire and solder it to Phono 2 switch 53 lug
# 1. '

13 [1 Select the orange wire and solder it to Phono 2 switch SB
lug #13.

14 E1 1n order to solder from the bottom of the board while the
wire is inserted from the top, place the preamp upright on
the left side, with the DH-102 on its end, against the side
panel. Place the black power supply wire under (behind)

y , ,m all of the existing (black) wires connecting to the eyelets
07;, 7 #1 1 on the power supply board. and solder it to one of the
62: .,.7 remaining eyelets #1 1. Since the eyelets on this board are

filled with solder, you may wish to clear them first with a
wooden toothpick. + 9

Connect the red wire to eyelet #12 near the front of the
board. An adjacent eyelet #12 has a (red) wire connected
to it. Make sure both wires are firmly soldered ~ 3
Connect the green wire to eyelet # t e rear corner of
the board. A (green) wire is presently connected to the ad-
jacent eyelet #3. Be sure both wires are firmly soldered.
Partially install .the bottom plate with two of the screws in
the sides.

Place the preamp flat. and position the DH-102 correctly,
with the switch protruding through the left hole in the bot-
tom plate. Makc sure no wires are either strained or trap-
ped. With the two screws supplied with the DH-102, fasten
it to the bottom plate. See that the wires stay clear of the
center bottom hole in the back panel.

install the remaining bottom plate screws. Insert the U"
shaped links in the External Patch sockets. unless these are
to be connected to other equipment. Do not push these
links in too far, or they may interfere with socket wiring.
Position the black power supply wire close behind the
other (black) wires to eyelets #1 1. against the board to the
front 1C, and then sharply bend it up to the grommet. Any
excess black wire should be pulled through to the other
side of the brace. once placement is correct. See sketch.
This positioning is essential for lowest hum and noise.

[51:1

16D

17D

18D

19B

200

21 1:1 The orange and blue wire to the Phono 2 switch can be
placed near the bottom alongside the circuit board. Make
sure all wires are clear of the top of the brace. and away
from the cover screw mounting holes, and install the cover.

22 El Place the self-adhesive label on the bottom so that it indi-
cates the higher gain position of the switch is towards the
left outside edge.

The switch handle may extend slightly beyond the feet on some
units. 1f this is a problem, you may obtain higher rubber feet from
the Haflcr Company for $1 to cover postage. Or. you may simply
choose to install washers under the present feet.

G951? 57.51

with:

(609) 662-6355