Case for DROK Amp Veloc

This is a protective case for the 50w x 2 mini-amp by DROK, as listed at the following link:

It is unknown if it will fit any other amps.

Wall o' Text follows...

First things first: The buttons are more of a basic "proof-of-concept" than actual functional buttons.  They *do* work, but they are difficult to use because of the tight spacing.  However, all of the buttons beyond the + and - are superfluous, since most people will be controlling their music playlist from their media device (cell phone, tablet, PC, etc..).  The exercise in design for the buttons was actually centered around how to make an effective and cheap sprung pushrod control assembly.  Specifics to be detailed in the appropriate section below.

I needed a case for the amp so that it could live outside without becoming stuffed full of dust and other weather-effects.  The case is designed around the limitations of ABS/ASA in regards to overhangs and layer adhesion.  Walls are fairly thin, but should be printable by most machines, and using most Styrene filaments.  Example print pictured was made using a .4mm nozzle, with some very specific pieces being printed using .35mm extrusion width.  Extra consideration was given to case-to-component clearances, to reduce and/or eliminate body gap for external openings.  Some post-process trimming is likely to be required for a proper fit.  Additionally, due to tolerance variation between the (admittedly cheap) amp board and the completed print, sanding/filing for fitment may be necessary.  To this end, the "shim" part is designed so that in case of extra-tight vertical clearance, it can be easily flat-sanded on the bottom to give those last few tenths.

The amp that this case was designed for comes with two plexi panels - top and bottom - which I have integrated into this design.  The bottom plexi panel is kept for rigidity, while the top plexi panel is kept to act as a window for the components.  I have to give credit where credit is due here, and say that this cheap amp has some of the best soldering I've seen for products at any price, so I wanted to let it shine through the top window.

Now to the nitty-gritty...

The top, bottom, and corner parts are straightforward.  Nothing special required, other than a good print bed to keep that ABS/ASA locked down tight while printing the top - it likes to warp, due to the narrow contact patches.

The shim is asymmetric, having a bit of a cutout on one end to accommodate a thin rubber sheet (more in a bit...).  The cutout aligns with the back-end of the top (where the screw terminals are located).

The "terminal bar" piece is primarily a beauty ring for the edge, but it also overlaps the shim around the channel opening so that it can pinch a membrane between the shim and the top and terminal bar pieces.  As a dust guard, I designed just enough clearance between parts at the terminal end to accommodate a thin piece of rubber - in my case, this was a rectangle cut from an old motorcycle tire tube.  Cut the rectangle, line it up  between the pieces, punch two holes for the bolts, affix everything together, then cut a slit down the middle of the membrane.  You can't see the slit in the photos, but it's there - good for keeping out dust.

Now, on to the buttons...

For most purposes, I would actually recommend using the "terminal bar" piece as a cover for the buttons.  Most of the buttons serve no functional purpose for most applications, so you would lose nothing by taking the easy road and going with a membrane cover.  The "button bar" piece has some very thin walls in places, due to the unfortunate placement of the surface-mount buttons on the PCB and their relation to the cutout in the plexi.  Using a narrow print nozzle is the best solution, but if that is not an option, reducing the extrusion width is required.  I saw good success going with .35mm extrusion on a .40mm nozzle, using KISSlicer to take advantage of the "crown" functionality (fills in tight spaces that a normal path would skip).  I also had to trim the top plexi by approximately 4mm on either side of the slot, to account for the clearance of the "Volume Down" button (it's really tight to the standoff).  The easiest way to know how much to cut is to simply attach the top cover to the amp over top the plexi panel, then mark it off with sharpie where the plexi sticks out into the slot.
For the buttons themselves, due to the tight space, it is recommended to print with a smaller nozzle, or print using no larger than .35mm extrusion width.

Now the fun part!

The holes in the button bar are sized to fit your typical cheap clicky ball-point pen spring and pen well.  If you've got some dead clicky pens kicking around, gut them for their springs and the (hopefully empty) pen well tubes.  Cut the tubes to length (apologies, I did not take measurements of the pen tubes prior to gluing - I cut them all to relative length for my board), glue one end into the "Button Pad" recess, insert up through the bottom of the "Button Bar", slide the spring over the tube, then glue the button caps onto the tube (inner surfaces of the socket on the buttons are sized to fit easily but not loosely onto the pen well tubes).  This likely sounds more confusing than it is, but should make sense when the pieces are in front of you.  Dry-fit all pieces prior to gluing, so you can dial in the correct length of the pen tubes to the buttons.  Also, the "Button NextBack" is used for both the "Back" and "Next" button pads, just reversed to point in the appropriate directions for their function.

I'm going to iterate on the overall button design, to try making them truly functional.  However, this is a very low priority, so it will be a while before I revisit the design.  Kinda burnt out on this project at the moment.


Test fit everything before committing to glue.  You may need to make some trims and adjustments along the way, depending on your slicer and printer.

Recommend using ABS/ASA or Nylon.  PLA could work for low-temp environs, but the heat generated by the amp itself might be enough to cause thermal failure.

Price Free
Category Household
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Uploaded 03/20/2018
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