Hafler DH-220, Xono Instructions For Assembly And Operation Manual

THE
POWER
AMPLIFIER
INSTRUCTIONS
for OPERATION
and KIT ASSEMBLY
CAUTION: IF THE SPEAKER FUSES BLOW, SOME DISTORTED SOUND CAN BE HEARD. THEREFORE
IF AMPLIFIER
MALFUNCTIONS, ALWAYS CHECK FOR BLOWN FUSES FIRST.
serial
number in all
communications
THE DAVID HAFLER COMPANY
5910 Crescent Boulevard, Pennsauken, New Jersey 08109
INTRODUCTION
The Hafler DH-220 is a two channel audio power amplifier designed to the very highest performance standards. It is available either as a kit, or fully assembled. Its 115 watt per channel power rating is sufficient for driving all loudspeakers in home applications, and its design assures extremely low distor­tion of all types. A combination of high performance, depend­ability, reliability, and moderate price is in the Hafler tradition of using the very latest technology to provide outstanding value.
The DH-220 circuit is a refinement of the DH-200 design, a
Hafler landmark which has achieved worldwide recognition,
and has elicited glowing reviews since its 1979 introduction. As in the DH-110 preamplifier, particular attention has been paid to component quality, using polypropylene or film capacitors wherever feasible, for example, for superior sound.
Combining the latest power MOSFET technology with uni­quely simple and effective circuit topology reduces distortion of all types, and at all power levels, over the full audio frequency spectrum, to the vanishing point. In addition to its pace-setting performance achievements, the conservative mode of opera­tion accomplishes a new high in long term reliability and
excep­tional resistance to abusive operating conditions. This is one of the direct benefits of MOSFET utilization in overcoming a serious limitation of conventional transistors
-
their tendency to self-destruct under other than normal operating conditions. So rugged is the DH-220 that it can deliver more than ten amperes into a short circuit!
The speed
-
measured as the slew rate - of this design
delivers unmatched transient linearity, revealing the most
delicate shadings, textures and nuances of the music, surpassing the capabilities of the most revealing loudspeakers and cart­ridges by a wide margin. Coupled with its unconditional stabili­ty, and ability to deliver adequate power into any loudspeaker load, the result is absolute freedom from listening fatigue. The longer you listen to this phenomenal amplifier, the more certain you will be that you could not have made a better choice.
The oversized power transformer and bridge rectifier; the massive heat sinks; the conservative operating levels of the MOSFET output devices
-
all are evidence of the design efforts to achieve exceptional reliability simultaneously with state of the art sonics and specifications. And this circuit is convertible to a high power monophonic amplifier with comparable stability and specifications.
The fully complementary, symmetrical push-pull circuit, which is direct coupled throughout (except at the input), incor­porates all silicon devices in a format which is directly related to the highly acclaimed DH-110 preamplifier. Its unique
self­protecting output stage prevents the thermal runaway which is a common threat to solid state amplifiers. The ruggedness and conservative operation of the output stage allows the DH-220 to avoid the need for special protective circuits which could com­promise audio performance. Basic protective systems provide maximum security against malfunction damage to the amplifier or the speaker: the AC line fuse, B + fuses, thermal breakers, and loudspeaker fuses. Nothing hinders the essential purity of the audio signal.
Those who use these instructions to assemble the DH-220 kit will find that the left and right audio modules (printed circuit and heat sink assemblies) are preassembled and pretested. This greatly simplifies the kit assembly so that it can be done in only a few hours without special skills or know-how. Because of
the modular arrangement, it is possible to operate on one channel if the other requires service, and avoids the need to return the en­tire amplifier in cases where only one channel is at fault.
Accessories for special applications include provision for monophonic use; a panel for standard 19” rack mounting; and an alternative power transformer for international AC line voltages.
Through advanced engineering geared to the audio perfec­tionist, and an efficient no-frills approach, Hafler is making high technology high fidelity affordable.
CONTENTS
Operation........................
Page 3
Assembly Instructions
..................
4
Wiring the Kit
......................
6
If Problems Arise.
.....................
10
Service and Warranty
..................
11
AC Line Connections for Overseas Use.
...
12
Kit Parts List
.........................
13
Schematic Diagram
...................
14
Component Value Listing.
..............
15
Pictorial Diagram.
..................
Insert
Copyright 1984, All rights reserved.
INSTALLATION
The
DH-220
is most likely to be installed out of sight in most applications, since its power may be controlled by the AC switching of most audio preamplifiers, like the Hafler DH-110. If your control unit does not provide switching capacity sufficient for the amplifier’s 7 amp needs (plus other equipment it is also switching), you should use the amplifier’s own power switch. In that case, turn on the preamplifier first; then turn the amplifier on a few seconds
after
the preamp has been turned on, to avoid any unnecessary turn-on transients from some preamplifiers. Likewise, switch the power amplifier off first.
If the amplifier is to be installed close to a record player, you should first check its position for freedom from hum pickup by the cartridge from the field radiated by the power transformer of the DH-220. Although the design of the transformer minimizes such radiation, certain cartridges are more sensitive
than others, and require separation from the amplifier. Check at
a comparatively high volume setting, and while swinging the
tone arm throughout its arc. Often a few inches additional spac­ing will eliminate the problem.
Be sure to provide sufficient
ventilation
for the amplifier.
Unobstructed
air circulation
around the finned heat sinks and
above
the amplifier is important for long, trouble-free life. Never put anything on top of the cover perforations. It is normal for the top and the heat sinks to become warm in use.
It is expected that the amplifier will always be resting on its feet, which should be on a hard enough surface that air flow underneath is not obstructed. If it is mounted in a rack, or through a panel, the feet may be removed so long as adequate ventilation is provided through the bottom openings.
OPERATION
The red pilot lamp which is integral with the power switch glows whenever the amplifier is turned on. A blown AC line fuse is the most likely cause if it is not illuminated when the amplifier is switched on.
The pilot lamp also provides a high temperature indication. In the unlikely event that the amplifier ceases to function, and the
amp blinks on and off steadily, it indicates that one of the ther­mal breakers has shut down the amplifier because of excessive temperature rise in a heat sink. When the heat has dissipated in a few minutes, the amplifier should return to normal operation. If the lamp again blinks, check for insufficient ventilation, or an excessive input signal, or an input which may have dangerous signal content (such as oscillation). Failing evidence of this, the amplifier may have malfunctioned. Because of the very large heat sinks, it is highly unlikely that any normal signal will cause the amplifier to overheat.
Loudspeaker Fuse Selection
The DH-220 power amplifier is supplied with 2 amp fuses in the speaker lines. Experience has shown that since an overload must exist for a few seconds for a fuse to blow, a 2 amp fuse will protect most speaker systems, and only blow when overload oc­curs. Smaller fuses tend to blow too easily, and larger fuses do not adequately protect most speaker systems.
A pair of 5 amp fuses are also supplied as alternatives for the speaker fuse holders. These should be substituted if the power output of the amplifier is to be tested, and these or intermediate values may be used if the amplifier is to be operated at very high power levels into 4 ohm loads.
If the manufacturer of your speakers recommends a specific
value of fuse for their protection, we suggest that you obtain
AC
fuses of that value and install them in the back panel.
Loudspeaker Power Ratings
There are no U.S. standards for rating the power handling of loudspeakers. As a result, the manufacturers’ usual “music power”ratings, or suggested amplifier limits, are of only minimal help in determining safe operating levels with amplifiers which can deliver substantial amounts of power. You must take into consideration the type of music, and the levels you like, to provide long term trouble-free operation of your speaker choice, when you have a sizeable amplifier like the DH-220.
Connections
AC
The AC power cord should be plugged into 120 volts, 60 Hz, on the switched outlet of a preamplifier which can provide at least 7 amps, or 840 watts. Then the amplifier power switch may be left on, and it will be controlled by the rest of the system. Or. it may be plugged into a 120 volt wall outlet, and switched on and off independently.
If your line (mains) voltage is different, be sure you have the
alternate power transformer which can accommodate several line voltages, and be sure it is wired for your mains voltage as described later in this manual
before you pIug in the amplifier.
Input
Conventional shielded cables, such as those supplied with your preamplifier, provide the input signal to the sockets on the back panel of the DH-220. Be sure that the outer shield connec­tion is secure, to avoid hum. The length of these cables (so as to permit remote location of the amplifier, if desired) is limited only by the output impedance of the preamplifier. If it is 600 ohms or less, as with the DH-101 and DH-110 Hafler preamps, for in­stance, cable lengths up to 50 feet are premissible without loss of
performance. Special low capacitance cables enable even greater distance between preamp 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 on the back panel. These binding posts provide several convenient alternative connecting 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 elements. A soldered end or fitting is the safest solu­tion.
These terminals also accept standard plug-in “banana pin con-
nectors,” 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 interchange speakers occasionally.
It is important to maintain correct phasing of the speakers when making their connections. Some speaker terminals are coded red and black, or + and
-,
etc. It is important that the “sense” of one speaker’s connections match the others. If one is reversed, you will find that the sonic image 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 suretheyare color coded, or that you follow
the indexing mark ononeside 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 recommended. 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 terminals 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 terminals
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 required at the volume
control. Some headphone boxes utilize a “common ground” system which makes it particularly important 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.
KIT ASSEMBLY INSTRUCTIONS
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-220 amplifier 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 necessary wire lengths in advance as you proceed. Fatigue increases the risk of error, so take a break rather than push to early completion. There are relatively few separate components in this design, to make it easy to pack everything away, if need be.
Your work area should have good lighting, the proper tools, and a place where the large pictorial diagram can be positioned within easy reach for checking. The tools should include:
1,
2.
3.
4.
5.
6.
7.
8.
9.
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. (Smaller diameters are easier to work with.) A damp sponge or cloth to wipe the hot top 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.
A soldering “gun” is
not
recommended. The unfamiliar user is more likely to damage the etched circuit boards with its higher heat potential and unbalanced weight. Also, because he may not wait long enough for it to reach operating temperature each
time it is switched on, poor solder connections are more likely.
Pencil irons are much lighter and easier to use, and there is no waiting time when solder connections follow in sequence, as in kit building. Make sure you have a holder for it, though, and
always unplug it when you take a break.
Proper Soldering
There are four steps to making a good solder connection:
Make a good mechanical connection to hold the wire in posi­tion while heat and solder is applied.
Heat
thejunction
of the wire and lug, or hole, with the bright,
shiny top of the iron. After heating for a couple seconds, apply solder to the junc-
tion. It should melt immediately and flow smoothly around both surfaces.
Allow the connection to cool undisturbed.
Remember that the connection is made by the solder, not by mechanically attaching the wire to the terminal. Usually the wire is looped through the lug and crimped in place, but some prefer to just place it through the hole and rely on the stiffness of the wire to hold it while soldering. Connections to numbered holes on the circuit board are handled this way.
Good solder connections are
essential
for trouble-free
noise-
free operation. A good solder joint does not require much solder
around the conductors. Never “butter” partially melted solder on the joint, as it is useless. A good connection looks smooth and bright because the solder flows into every crevice when the parts are hot enough. The iron must have a bright, shiny tip to transfer heat easily to the junction. That’s why the damp sponge should be used frequently to wipe the tip, and occasionally you must add a small amount of solder to the tip, too. If a connection is difficult to heat, “wet” the tip with a small blob of solder to pro­vide a bigger contact surface to the joint. Once the solder flows around the conductors, any movement must be avoided for a
few seconds to allow a good bond. When cool, check the con­nection by wiggling the wire. If in doubt, or if the connection is
not shiny, re-heat the joint. Excess solder may be removed from a connection by heating it and allowing the solder to flow onto the iron, which is then wiped on the sponge.
ALL SOLDER USED MUST BE ROSIN CORE.
Never use acid core solder or any separate flux in electronic work. Silver solder is also not suitable. If in doubt about unmark­ed solder, always obtain a fresh supply of rosin core solder. We recommend 60/40 for easiest use. Do not confuse it with 40/60, which is harder to melt.
The general procedure is to use a hot iron for a short time to heat a connection, then add solder with the iron still in contact. Remove the solder once it flows, and then remove the iron. A cooler iron applied for a longer time is more likely to damage components, or lift the copper circuit pattern from the boards. A break in the etched circuit can be mended by simply soldering a small piece of wire across it. Do not allow much build-up of solder on the tip of the iron, or it may fall into adjacent circuitry.
When soldering to a numbered hole on the board, insert the wire from the components side, and apply the iron, leaving some bare wire exposed so that you can see that the hole is then filled with solder for a secure bond. A round wooden toothpick is suggested so that you can heat and clear the hole of solder if it hinders your inserting the wire. Some builders prefer to clear every hole first with a touch of the iron and toothpick. If the wire has first been “tinned,” no additional solder may be necessary if
solder fills the hole, but it is good practice to push the wire through, and then back it up a bit, to be sure solder fills the hole
from both sides. Make certain a bright, shiny flow is evident from the wire, across the hole, onto the circuit pattern on the
board.
“Tinning” refers to the process of applying a light coating of
solder to the bared wire end. This keeps all the strands secured, and also makes a good connection easier. Simply touch the wire with the iron for a couple of seconds, and apply solder. Allow the excess to flow away onto the iron. When properly done, the wire is uniformly bright, and no larger than before. The hookup wire supplied with this kit does not normally need tinning, for it is pre-tinned.
5
Wiring the Kit
If any components are unfamiliar to you, checking the pic­torial diagram should quickly identify them. Or, the quantities, and the process of elimination as you check the parts list, will help. The pictorial diagram is necessarily distorted to some ex­tent for clarity, so that you can trace every wire in a single overall view for verification as you work. You may wish to check off on the diagram as you solder each location.
To “prepare” a wire means to cut the designated length from
the coil of that color, and strip about
1/4"
of insulation from each
end. The wire supplied in the kit is
#18,
so you can set adjustable
wire-strippers accordingly. The transformer leads are
#16
or
#18
and the line cord is
#16.
Be careful that you do not nick the wire when you strip it (that can happen more easily if you do not use wire strippers) for that weakens it. The wire supplied in this kit is “bonded stranded,” which provides exceptional flexibility with resistance to breakage for easier use, and it is pre-tinned.
Whenever a connection is to be soldered, the instructions will so state, or indicate by the symbol (S). If more than one wire is to be soldered to
the
same terminal,
they
will be indicated by (S-2),
(S3),
etc. If soldering is not called for, other connections have yet to be made to that terminal. They would be more difficult if the connection was already soldered. Every connection in the kit will be soldered when it is complete. After soldering a con­nection, it is best to clip off any excess lead length to minimize the possibility of a short circuit (as on switch lugs, where ter­minals are very close together), and for a neat appearance.
Be sure that uninsulated wires cannot touch adjacent ter-
minals or the chassis metalwork.
The symbol
(#)
indicates a connection is to be made to that point. When a lug number is specified without (#) it is simply a locating reference.
When the instructions call for twisting two or three wires together, the length of wire indicated anticipates a fairly tight, uniform twist by hand, of three full turns every two inches. If
you find the wires too short, loosening the twist will gain some
needed length.
Handle the circuit boards carefully. They represent a major
part of the kit cost. Stand-up components, such as transistors,
should be checked when you install the module, to be sure all
leads are separated.
All of the active circuitry is contained on the PC-19 board,
which has been carefully tested to assure that it meets every
specification. Only the interconnection of power supply
elements is left to the builder. Take the time to be accurate and neat, and you can be sure that your completed amplifier will meet the performance of a factory assembled unit, and can con­tinue to perform properly for years to come. Check your work, and make sure the entire step has been completed before plac­ing a check mark in the space provided, and continuing on to the next step.
KEP nuts have been supplied as a convenience. These have lockwashers attached, and the lockwasher always goes onto the screw first. If the sheet metal screws have hex heads, you may
find it easier to first start them with a regular screwdriver, to set the thread, and then use the more convenient nut driver, if one is available.
Mechanical Assembly
1 r When you unpack your kit, you will find that the
transformer, large capacitors, and the output assemblies have been temporarily fastened to the chassis for safe shipment. Disengage these, and include this hardware with the rest when you check off the components against the parts list in the back of the manual. We recommend this check-off to be sure you have everything, and to enable you to identify any unfamiliar items by comparing them with the pictorial diagram. An egg carton is ideal for keeping hardware items separated.
A “set” of hardware includes one screw and one KEP nut (with its attached lockwasher). Always install the lockwasher side of the nut first. If the size of the hardware is not specified, use the
#6
size. The smallest size is
#4
and
#lO
the largest. Always insert
the screw from the outside of the chassis. It will simplify matters if you first separate the
#4
nuts from the
#6
nuts, which have the same outside dimensions. A #4 screw
will pass through a
#6
nut, aiding identification.
2
L
Select the four rubber feet, four sets of #6 hardware, and
the chassis. Insert each screw through a foot so that the head is recessed, and install the feet on the outside at each corner hole.
3
1
Select th
e wo red output terminals. Install them in the
t sequence shown below, in the two center holes LR and RR marked
'
+’
at the rear of the chassis. Before you fully tighten the first nut, unscrew the cap to expose the hole drilled through the threaded shaft. Connection of loud­speaker wires will be easier if these holes are positioned vertically. A nail through the hole will keep it positioned while the hardware is tightened. Each connecting lug should point downward before the last nut is secured. Be sure both nuts on each terminal are
tight,
as they are dif-
ficult to reach when the amplifier is completed.
4 Select the two black output terminals and install them or
either side of the red ones, at LB and RR. Be sure the shaft holes are vertical, the lugs point downward. and each nut is tight.
6
5 n Select the two round fuse holders, and two each
1/2”
rub­ber washers, lockwashers and nuts. First install the rub­ber washer on the holder, so it will be outside the chassis, and then fasten the fuse holders at LF and RF, with the tip lugs pointing towards each other, toward the center of the chassis.
6
U Select the two input sockets and 4 sets of #4 hardware.
Install the sockets
inside
the chassis at LS and RS so that the short lug of each socket is near the hole between the two sockets.
7
0
Select the single ground lug (with lockwasher teeth) and
one set of #4 hardware. Install it between the input sockets, pointing toward the bottom. Bend it out for ac­cess, and twist it
90°
for easier insertion of a wire later.
Be sure this lug is
tight,
as the locking teeth must cut
through the chassis paint for a good ground connection.
8
ri
Select the four-lug diode block DB, the long #6 screw,
and a nut. Install the rectifier in the center hole near the rear of the chassis, with the plus
(+)
terminal located over the tiny indexing hole at position four. Correct orientation of this rectifier is
essential
for proper wir-
ing.
9 n Select the single fuse clip, and one set of #4 hardware. In-
stall the clip in the right front chassis hole FC, closest to the foot.
10
0
Select the two dual fuse clips and four sets of #4 hard-
ware. Install these in the pairs of holes FL and FR on either side of the center of the chassis.
11 0
Select the
5-lug
terminal strip and two sets of #4 hard­ware. Install it in the front holes TS, next to the single fuse clip. Note the position of the mounting lugs (to the right) in the pictorial diagram.
NOTE: Kits provided with the multiple voltage power transformer
for use in locations outside the United States having a line (mains) voltage other than 120 VAC are also supplied with an additional two­lug terminal strip which is to be installed using an additional set of
#4
hardware on the other side of the chassis, below the dual fuse clip FL.
12 0 Select the power switch. Install it with the red window to
your right as viewed from the front. The switch snaps into chassis hole PS from the outside.
13
q
Select the AC line cord and the plastic strain relief. Separate the two conductors for 2”. Cut 1” off one of the two leads, and strip
1/4"
of insulation from each lead.
Twist the strands tightly, and tin each end. Make a sharp
'V'
in the cord
8 1/2"
from the longest cut end by bending it
back on itself. Install the relief with the small end nearest
the cut end of the cord. Crimp the two halves of the relief
around the wire at the
'V'
with heavy pliers, to partially
form it before insertion into back panel hole AC. Then
grip the larger diameter with the plier tips, squeeze it tightly, and insert the cord and the relief from the out­side. A flat side of the relief mates with the hole shape, and it snaps into position when fully inserted.
14
15
16
170
18
0
Connect the shorter lead to FC lug
#l.
(S). Connect the
longer lead to the
lower
hole of TS lug
#2.
(S). Note that
lug 2 is the second protruding lug on the terminal strip. It
is
not
the mounting bracket for the terminal strip. Soldering this lead to the lower hole now will make later connections to the top portion of the lug easier. Be sure no stray strands of either line cord conductor are left unsoldered.
Prepare a
6 1/2"
green wire. Connect one end to dual fuse
clip FL lug
#l.
Connect the other end to the other dual
clip FR lug
#l.
(S).
Prepare a
6 1/2"
white wire, Connect one end to FR lug
#3.
Connect the other end to FL lug
#3.
(S).
Prepare two 7” white wires. Start with one wire project­ing
3/4"
beyond the other, and twist them uniformly
together throughout their length. Connect the project-
ing end to RF lug
#l.
(S). Connect the corresponding end
of the other wire to
RFlug #2.
(S). Place this pair over the
right edge of the chassis.
Prepare two more 7” white wires. Start as before with one wire
3/4"
longer, and twist them together. Connect the longer end to LF lug #2 (S). Connect the other wire to LF lug
#l.
(S). Place these wires off to the left.
Prepare an 8” green wire and a 10” white wire. Start with the white wire
3/4”
longer than the green wire, and twist them uniformly together. Connect one end of the green wire to the lug on black output terminal LB. Con­nect the corresponding end of the white wire to red terminal LR. (S). Place these wires off to the left.
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