Mechanics (Updated march 2018)


The ideal enclosure for a Pre amplifier is a Faraday cage or closed metal box. Since that is not the most elegant solution I looked for a mid-way alternative.
The hight of the Pre amplifier enclosure is pretty much determined by the display plus openings for the IR and visible light sensors and came out at 100mm.
The width and depth were determined by the Pre amplifier main board plus power supply boards and came out at a little under 400mm wide and 260mm deep.
That were the outer dimensions of the metal box with a 1.5mm oversize of the front and back plates to make it a bit more attractive.
I decided to make my life easy and had all the holes and outer dimensions of the front, back and side plates of 4mm thick aluminium cut out by a company specialized in water cutting. They also cut out the top and bottom plates of 1.5mm thick aluminium.
To assmble all the parts of this box I used 10mm square aluminium rods that I milled at the correct lengths on a small metal milling machine.
I tapped threads in the front, back and side plates and secured the rods with screws and added 2 additional rods to mount the Pre amplifier board. The display board was mounted on the rods of the front plate with spacers.
Two holes were drilled in the front plate of 3mm diameter and acryllic rods were mounted in the holes as light guides for the IR and visible light receivers.
The front side opening for the display and all the backside openings for the connectors were chamfered on my milling machine with a 45 degree metal chamfer mill to give it a professional look.

After I completed all metal work I had all the aluminium anodized in a black color but kept the front transparent anodized.
In order to keep my "Faraday cage" concept I removed the anodization layer at the places where the screws are located. The top and bottom plates were mounted with spring rings to connect them electrically to the rods. In this way the whole casing is electrically conducting and resembles closely to a Faraday cage.
This helps a lot to shield especially the Phono amplifier section against external mains noise.
I finished the enclosure with text labels on the back plate indicating the different inputs and outputs, power inlet and USB power outlet.