Do you want to make a one-off, or multiple copies? This is the main factor controlling the enclosure design.
When you know whether you just want to build one, or produce a design for manufacture, many choices are simplified.
What displays, controls and I/O sockets are required, including power inlet and fusing?
How much money do you want to spend?
If you just want to build a single item, you can proceed with an unmodified working prototype. Simply buy a large enough (oversize) off-the-shelf (rackmount?) enclosure with a sufficiently large fascia to accommodate the display, controls and sockets. Do a rough sketch of your intended layout and proceed with the handwork, i.e. drill and pierce the case and install the individual components, run the connectivity.
If your intention is to produce a design that will appeal to other builders, it may be sufficient to leave it in the form already described, but depending on the exact intent, some consideration can be given to style, cost and ergonomics. Very often the best procedure is to try to imagine the the device in use.
Inputs and outputs are sometimes arranged with a general sense of flow from left to right. Sometimes it is more convenient to have inputs on the back, but sometimes they are more conveniently or conventionally placed on the front. This can influence the final layout of any PCB. Most modern designs use modern manufacturing practices and pots, switches or sockets are PCB mounted, sometimes with support provided by the chassis or enclosure structure.
As a general rule the ON/OFF switch is placed at the extreme left- or right-hand position, and is the largest of the switches, regardless of the actual power carried. The opportunity can be taken to make this switch illuminated, and thereby indicate status.
Look at a piece of equipment you use regularly and attempt to learn from its layout.
Hi counterCulture, mickeymoose.
Thanks for the questions.
Here is the overall plan:
1. I would like to build only one unit.
2. Don't want to spend more , willing to use wood wherever possible.
3. The front panel probably will be aluminium :
- a. It would have one power button (illuminated with blue LED) at left end
- b. A 20-channel spectrum display.
4. On the back panel:
- a. Input L+R audio channels.
- b. Output L+R audio channels (internally connected to input).
I recommend building it using glass blocks (or the plastic equivalent) with high-power LEDs behind each block. This will be rather large, but will look freaking awesome.
OK, maybe that's not so practical, but... consider leaving an option to plug in an external display. Perhaps not as big and bulky as glass blocks, but a display that hangs on the wall: how about LEDs behind frosted plastic, or the kind of diffuser panel that's used with fluorescent fixtures in dropped ceilings?
The usual suppliers (Mouser, Digikey, etc.) sell general purpose plastic/aluminum "Instrument cases" .
There's even some with a transparent red front panel, so display LED segments show through without cutting a window.