For the purposes of this article, we’ll generally assume that you’re building the unit from a kit and that the case comes with all the holes pre-drilled. If not, then you will have to drill the holes yourself using the photographs and the layout shown in Fig.12 to guide you.
As previously stated, if you have to buy a case separately, then we recommend the Altronics H-5035 rack case.
Basically, you will have to drill/cut holes in the front panel for the mains switch, the earth point (4mm), the three pushbutton switches (10mm) and the two LEDs (5mm). You will also need a 5mm hole for the IR receiver plus four 3mm mounting holes for the Switch Board. Note that the Switch Board is directly attached to the front panel and not mounted on a sub-panel as in the prototype.
Make sure that the cut-out for the mains switch is the correct size, so that it snaps securely into place and is retained by its plastic locking tabs. This involves drilling a series of holes inside the marked cut-out and then carefully (and tediously) filing it to shape. Alternatively, you can use a toggle switch that requires a round mounting hole but make sure that the switch is mains rated.
On the rear panel, you will need clearance holes for the various input and output sockets, holes for the fuseholder and rear-panel earth point (4mm) and a cut-out for the IEC socket. An alternative here is to use an IEC socket with an integral fuse, in which case the external fuseholder is no longer necessary.
Drilling the bottom of the case is straightforward. First, use the PC boards as templates to mark out their mounting holes. Note that the Input and DAC boards sit right at the rear of the chassis and their sockets must be correctly aligned with their rear panel holes to avoid shorts. Drill these holes to 3mm, then drill two 4mm holes for the earth points plus a mounting hole for the transformer. Having done that, fit four feet to the bottom of the case if it doesn’t already have them. These can be either a self-adhesive type or you can use bolt-on feet in which case you will have to drill the necessary holes.