Published:2011/8/4 1:42:00 Author:Amy From:SeekIC
Ton Giesberts
Assembly
For our prototype, we chose the ’not so quick-and-dirty’ method and fabricated our own enclosure from a sheet of aluminium. This results in an unconventional design, whose shape and proportions are determined by the dimensions of the heat sink, toroidal transformer, power-supply capacitors and power supply board (Figure 2). The heat sink forms the front of the unit. The mains entry, input sockets and speaker connectors are fitted at the rear. Of course, you are free to package everything into another type of (standard) enclosure.
In our design, we tried to keep the power supply connections as short as possible, and we fitted the power supply board above the large toroidal transformer. The four fastening holes for this board are far enough apart to allow it to be secured to the base with ample clearance from the transformer. The two rows of four electrolytic capacitors each are placed next to each other in a single group. Their terminals are connected together using small 2-mm aluminium plates. Be sure to provide adequate separation between the plates for the +, 0 and - polarities. We recommend fitting screw-mounted flat connectors to the plates, to simplify wiring and maintenance.
The capacitors can be adequately secured using four mounting clamps. Where necessary, one mounting tab must be broken off of each clamp.
The wiring diagram is shown in Figure 3, which also shows the filter boards. These still have to be described.
The two centre taps of the transformer (neutral/ground) are connected to one side of the common ground plate for the electrolytic capacitors, between the plus and minus leads from the bridge rectifier. In our design, the bridge rectifier is fitted to the side panel, which provides it with an adequate cooling surface.
On the opposite side of the electrolytic capacitors, the three power supply terminals (including neutral) are connected to the terminals on the power supply board marked with ’input’ arrows. The four terminals for the supply voltages are thus available on the power supply board. The path to the amplifier board must be as short as possible. This also applies to the 10-V auxiliary voltage!
For the main supply voltage, stranded wire with a cross section of at least 4 mm2 must be used. The mute signal for the amplifier is generated on the power supply board. It is connected to the amplifier board using a twisted pair of small-diameter stranded wires. The analogue supply voltage is connected to the amplifier board using a twisted pair of stranded wires (1.5 mm2).
The mains voltage output from the power supply board is connected directly to the large toroidal transformer.
There is room to fit a small fan on the rear panel for internal cooling, if so desired. Try to route the cables for the input signals as far away from the transformers as possible. The loudspeaker leads must be wired as a twisted pair for each channel to counter the effects of interference fields.
Reprinted Url Of This Article: http://www.seekic.com/blog/project_solutions/2011/08/04/ClariTy_2x300W_Class_T_Amplifier_Part_3__power_supply_assembly_and_alignment_(4).html
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