Hafler DH-200 Assembly And Operating Instructions Manual page 4

tance cables enable even greater distance between preanip
and amplifier. It is desirable to keep the left and right input
cables close together throughout their length to minimize the
likelihood of hum pickup. Also, you should avoid running
them parallel to AC cords — these should be crossed at right
angles.
Output
The loudspeakers (or headphones) connect to the red
and black terminals in the center of the back panel. These
binding posts provide several convenient alternative con­
necting methods. The screw cap may clamp the bared wire
end, or a "spade lug" attached to it, but a better connection
will be made by locating the hole drilled through the shaft of
the terminal when the cap is unscrewed. Insert the twisted
end of the bared wire so that the cap will clamp it in place.
Always be sure that no strands of wire are unsecured, and
that the bared end is not too long to risk contacting other ele­
ments. A soldered end or fitting is the safest solution.
These terminals also accept standard plug-in "banana pin
connectors," including the double ones with standard 3/4"
spacing, available from electronic supply houses. These are
the most convenient, especially if you may wish to in­
terchange speakers occasionally.
It is important to maintain correct phasing of the
speakers when making their connections. Some speaker ter­
minals are coded red and black, or + and —, etc. It is im­
portant that the "sense" of one speaker's connections match
the others. If one is reversed, you will find that the sonic im­
age has a "hole in the middle," and that it is deficient in bass.
Speaker wire always identifies one conductor to make this
easy. There may be a molded ridge in one lead, or the color
of the insulation on one wire is different, or the wire itself
may be color coded. If pin plugs are used, be sure they are
There are three basic rules for success in electronic kit
building:
1. Read the instructions carefully, and follow them in
order.
2. Make secure solder connections which are bright and
smooth.
3. Check your work carefully after each step.
The DH-200 preamplifier is a versatile component with
sophisticated circuitry which has been made remarkably easy
to build by individuals with many years of experience in the
design and engineering of the finest performing audio kits,
and in the preparation of their manuals.
Kit building should be fun, and we are certain you will
find this to be so. Assembly will be faster, easier, and more
enjoyable if you have someone help you by reading the steps
aloud, selecting the required parts, and preparing the neces­
sary wire lengths in advance as you proceed. Fatigue in­
creases the risk of error, so take a break rather than push to
early completion. There are relatively few separate compo­
nents in this design, to make it easy to pack everything away,
if need be.
color coded, or that you follow the indexing mark on one
side of the double connectors.
Select speaker wire of sufficient size to preserve the high
damping factor (and excellent speaker control) of your
amplifier. Standard 18 gauge lamp cord ("zipcord") is
satisfactory for distances up to 30 feet for an 8 ohm speaker.
As the distance increases, larger wire sizes are recom­
mended. The next larger wire size is #16, and it is often
preferred by perfectionists. If you have 4 ohm speakers, the
maximum cable length for best results is halved.
The black output terminals are electrically connected to
the chassis internally. Be certain that when the amplifier is
operated in its normal stereo mode that the red output ter­
minals are never connected together. In the special case when
the amplifier has been internally modified for monophonic
bridged operation, the output is taken from the two red ter­
minals only. Then, the black terminals are left unconnected.
Headphones are normally operated from the loudspeaker
outputs, but are usually connected through a junction box
which provides switching from phones to speakers. Such a
box usually provides some added resistance to reduce the
sensitivity of the phones, and thus minimize the likelihood of
hearing component noise, because of the low setting re­
quired at the volume control. Some headphone boxes utilize
a "common ground" system which makes it particularly im­
portant that you carefully observe the proper connections.
While the black ground terminals can be connected together,
the red ones must not be.
Some headphones, such as electrostatic types, are less
sensitive and may need little or no resistance in series for
normal operation. These could be easily interchanged with
the speakers through the use of double banana plugs.
ASSEMBLY INSTRUCTIONS
Your work area should have good lighting, the proper
toots, and a place where the large pictorial diagram can be
tacked to the wall within easy reach for checking. The tools
should include:
1.
2.
3.
4.
5.
6.
7.
8.
9.
4
A 40 to 100 watt soldering iron with a 1/4" or smaller
tip which reaches at least 600°F.
60/40 (60% tin) ROSIN CORE solder, 1/16" diameter
or smaller.
A damp sponge or cloth to wipe the hot tip of the iron.
A wire stripping tool for removing insulation. This can
be a single-edge razor blade, but inexpensive stripping
tools are safer, faster and easier.
A medium-blade screwdriver (about 1/4" wide).
Needle-nose pliers (a long, narrow tip).
Diagonal or side-cutting small pliers.
Large "gas" or "slip-joint" pliers.
A 1/4" "Spin-tite" nut driver may be helpful, but is not
necessary.