INSTRUCTIONS FOR
THE HAFLER
DH-222
AMPLIFIER BRIDGING KIT
FOR THE DH-220
The DH-222 may be installed in a Hafler DH-220 power
amplifier to enable easy conversion to a high power
monophonic amplifier, bridging the two conventional chan-
nels to a single floating output which can deliver in excess of
400 watts into an 8 ohm load. Its rated power output is 350
watts across the audio band.
When switched to monophonic operation (UP), signal input
should be provided to the LEFT input jack only, and the output
should be connected only to the two center BED
( +)
terminals.
No connection of the load is to be made to the black output
terminals. Because of the floating output, neither side of the
load may be grounded. Thus it is unlikely that stereo speaker
switching boxes, or headphone adapters may be used, as these
often have a common ground between the left and right chan-
nels.
The speaker fuses may be replaced with higher values than
the 2-5 ampere range suggested for stereo operation, if de-
sired, depending on the degree of protection for the speaker
which is intended. The graph shows the nominal sustained
power output limit of a 7 ampere standard fuse, which is the
maximum recommended value. Smaller values will provide
more protection for the speakers; larger ratings are at the
user’s risk.
fuse blows in mono operation, both should be replaced, for it is
likely that the second has been weakened. For equivalent load
impedance, each speaker fuse provides the same power output
protection as in stereo operation.
With the internal conversion switch DOWN, the amplifier
functions as a conventional stereo amplifier, with normal
input and output connections. The minimum recommended
load impedance, which is limited only by thermal factors (abil-
ity of the heat sinks to dissipate high energy levels), is 6 ohms
in mono; the usual 3 ohms in stereo. The amplifier circuit can
safely accommodate lower impedance loads, of course.
The conversion, which takes less than an hour, involves
only changes to the input wiring, and installation of the switch
with its mounting bracket and one resistor. These instructions
assume familiarity with the usual kit building descriptions,
and reminders. For more details in this regard, see the con-
struction section of your DH-220 amplifier manual. You must
be certain you have made a good solder connection wherever
one is called for, not only to the wire you have attached, but to
any others already connected to that point. The notation (
S)
indicates a soldered connection; (S-2) denotes that there are
two wires to be soldered. Use only 60/40 rosin core solder. Be
careful not to let the soldering iron touch adjacent components
on the circuit board: excessive heat could change their opera-
Both speaker fuses should be the same value. If one speaker tion, with the possibility of damage to the amplifier.
KIT PARTS LIST
Switch, DPDT
Mounting bracket
Indexing washer
Lockwasher
Nut, switch mounting
Nut, 6-32 KEP
Screw, machine, 6-32
Resistor, 3000 ohms
Wire, red, 22 gauge
Wire, green, 22 gauge
Wire, black, 22 gauge
sz114
MS183
HW123
HW122
HK125
HK112
HA116
12 16
RESISTIVE LOAD IMPEDANCE
LIMITED WARRANTY
The
parts in the DH-222 are guaranteed against defects for one year from the date of purchase. Installation in a DH-220
amplifier is the owner’s responsibility. In the event of difficulty with the completed unit, charges for service, if any, will be in
accordance with the warranty provisions for the amplifier, if it was purchased as a kit. If it was purchased as a factory
assembled unit, there is the further stipulation that faults incurred as a result of improper installation of the DH-222 are the
owner’s responsibility, but in other respects the original warranty applies. This warranty gives you specific legal rights. You
may also have other rights which vary from state to state.
5910 CRESCENT BOULEVARD, PENNSAUKEN, NJ 08109.609/662-6355
LM056
