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Design of a Korg Nutube Amplifier Part 5: Finishing Touches

Adding a custom laser cut enclosure, dials and a protective case.

This post picks up where Karl previously left off and we look at the design of a custom laser cut enclosure, together with adding potentiometer knobs, PSU and a protective case for transportation.

A particularly cool design such as this deserves a suitable enclosure to do it justice and ideally one which allows you to see the Nutube glowing during operation. With this in mind, it was decided to create a custom laser cut enclosure. However, one challenge with these is making a box that is both fully enclosed — like traditional valves, the Nutube is to some extent microphonic and benefits from being enclosed — and aesthetically pleasing, e.g. doesn’t have bolts all over the place.

Handily, a solution was found in the form of laser-cut elastic clips from Patrick Fenner, which are described as “A laser cut clip for acrylic that allows self-locking 90-degree joints between parts using no additional hardware.”

The base panel can be seen centre-right, with the front panel above it and sides below. Centre-left we can see the controls section of the top panel, which is affixed to a window section above. The rear panel is below these. The controls panel is cut from 4mm cherry veneer MDF to give a retro feel to the design, with the window and everything else cut from 3mm acrylic. For those not familiar with laser cutting, different colours are used in the drawing so as to allow different power levels to be assigned during cutting. E.g. here black = cut, while red and blue = etch (lower power).

The design was the idea of my colleague, Dave, who completed this in Inkscape and he can be seen pictured above with panels fresh out of the laser cutter.

So as to give a protective finish to the cherry veneer MDF and prevent it from picking up finger marks, it was put in the spray booth and given a thin coating of Briwax spray.

Once the coating had dried the two parts of the top panel were assembled together, with M3 dome head hex machine screws used to secure these.

The potentiometers were de-soldered from the PCBA and short lengths of ribbon cable used in their place, which were then connected on the other end to the panel mounted potentiometers. Note that the shafts had to be cut down to around 12mm, which was easily done with a junior hacksaw.

Now the others parts of the enclosure could start to come together and the PCBA was secured to the base via 4x M3 machine screws, with 3mm circular spacers under the board.

RS Pro potentiometer knobs of 16.2mm diameter (259-6935) were selected, with a black body and red cap, so as to complement the midnight black acrylic base and frosted red acrylic rear panel.

 

A Peli Storm case (111-1043) was selected to protect the finished pre-amp and 12VDC power supply (121-7133) during transportation.

The sticker was removed from the case and in its place, a laser cut badge affixed. The etched lines filled with white wax so as to increase the contrast and make the text more legible.

And there we have it: a cool little pre-amp based around the Korg Nutube, packaged in a smart custom laser cut enclosure and with a protective case for transportation.

Should you like to have a go at making your own, the DesignSpark PCB and acrylic enclosure design files can be found in the nutube-preamplifier GitHub repository.

Andrew Back

Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.