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Housing your unit
The PCB has been designed to fit into a standard 1U high 19" rack unit. Your local parts
distributor will probably have these. Good rack units are quite expensive, and will contribute
heavily to the final cost of your completed Filtrex. Expect to pay around 35GBP or so.
In the UK the ones I recommend are made by Bryant Broadcasting or Holt Broadcasting
Services. You can use the Schaeffer Frontplatten database provided on the project webpage as
a template for any drilling of holes in the front panel.
The Bryant and Holt ones are superbly made, but they do not allow you to use a 3mm thick
Schaeffer front panel in place of their own. Their cases actually utilise the front panel as part
of the enclosure. Simply swapping the Bryant or Holt panel with one obtained from Schaeffer
will not work as the case would no longer be able to held together. Bryant and Holt do
custom metal work, so it may be possible to try their services. This is one area I would like to
try in the near future.
Schaeffer, and their US franchise Front Panel Express, are also able to engrave panels that are
sent to them. One could send them the blank Bryant panel and they could engrave this with the
Frontplatten database found on the Filtrex website. I have heard from one person who has
tried this and he was very pleased with the result. Remember if you do decide to do this, you
must remove the four mounting holes from the Frontplatten database before sending it to
Schaeffer or Front Panel Express as these are already present on the Bryant panel. I am not
sure whether this could be successfully done with the grey painted finish of the Holt panels.
A Schaeffer FPD file can be found on the Filtrex's project webpage which can be downloaded
and edited. If printed out at 100% size and in 'wire mode' with reference points, you can then
use it as a template for drilling your own front panel holes.
My current favourite method of labelling a front panel on one of these empty rack cases is to
use a thin (1.5mm) engraved black anodised aluminium 'overlay' panel from Schaeffer. This is
held onto the main case's front panel by three or more 3mm screws at suitable points along
overlay and the components simply stick out the holes in the overlay. The pot nuts are secured
to the front panel of the rack case which hold the board in place. Once the PCB is fitted and
tested the overlay can then be secured into place. The pot holes in the overlay will need to be
sufficiently large enough not to snag on the pot nuts and washers and the FPD should be
edited accordingly. I use 14mm diameter holes in the overlay which are big enough to not foul
the pot nuts but are small enough to be nicely covered up by the control knobs. The LED
holes need to be 3.2mm and the switch hole 7mm.
If you buy the rack cases made by Vero, you will find that the height of the unit internally is
quite restricting. The bottom and lower panels have 6mm folds in them at the front. This
affects the amount of space available for the pots and circuit board at the front panel. It is
possible to use these cases as I have done in the past but you will need to mount the board
high enough on the front panel to prevent the pot pins shorting with the case.
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