Hafler DH-200 manual KIT Assembly Instructions, Output

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 drill- ed 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 contac- ting other elements. A soldered end or fitting is the safest solu- tion.

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 sure they are 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 satisfac- tory 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 perfec- tionists. 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 com- ponent 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 ter- minals can be connected together, the red ones must not be.

Some headphones, such as electrostatic types, are less sen- sitive 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, selec- ting 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, A 40 to 100 watt soldering iron with a 1/4" or smaller tip which reaches at least 600°F.

2.60/40 (60% tin) ROSIN CORE solder, 1/16" diameter or smaller. (Smaller diameters are easier to work with.)

3.A damp sponge or cloth to wipe the hot top of the iron.

4.A wire stripping tool for removing insulation. This can be a single-edge razor blade, but inexpensive stripping tools are safer, faster and easier.

5.A medium-blade screwdriver (about 1/4" wide).

6.Needle-nose pliers (a long, narrow tip).

7.Diagonal or side-cutting small pliers.

8.Large “gas” or “slip-joint” pliers.

9.A 1/4" “Spin-tite” nut driver may be helpful, but is not necessary.