Bass guitar preamplifier in the Ampeg SVT tradition

Designing and fabricating the front panel

The front panel took a long time to reach its final form.  Below I summarize how I designed it and had it fabricated.


I designed the first version of the front panel with Microsoft Visio 2003, and made it myself using the front panel blank supplied with the Par-Metal enclosure.  I used a drill press and a step bit to make the holes for the controls, and normal drills to make the anti-rotation holes.  It came out perfectly - all the controls fit into the panel, and the panel fit the enclosure.  Here is my unlabeled hand-fabricated panel:
hand-fabricaled unlabeled front panel

Toner transfer / copper sulfate etching experiments

However, I wanted professional-quality lettering for the control labels.  I spent quite a while attempting to do this myself using the toner transfer technique and chemical etching, but my test etchings did not achieve the quality of result I was seeking. Here is one of my toner transfer etching experiments, performed on my Fender Blackface control panel wiring fixture/template.  All the extra holes are preexisting features of the scrap aluminum I used to make the template.  I wasn't able to get a high enough toner density with my printer to prevent unwanted etching of the background.  I'm still enthusiastic about the capabilities of the toner transfer and etching process, but I need more time to refine my process. I'm going to try again with a better printer on a future project.
Experiment using toner transfer and copper sulfate
              etching process

Front Panel Express

I reluctantly abandoned my efforts to do the panel labeling myself, and used the Front Panel Express design software and CNC fabrication service to realize the front panel.  Initially I was not eager to use their proprietary design program to re-do the panel.  However, it turned out that the software was not difficult to learn. The positions and dimensions for the control holes, blind holes on the back side for the anti-rotation tabs, and labels are easily entered and refined. Since the Front Panel Designer (FPD) software is optimized to feed into their fabrication process, the designer can be confident that the panel will be manufactured exactly as designed.  The cost for each feature is tabulated as the design proceeds, so you know exactly what the panel is going to cost.

A few things I learned:
  • Minimize the labeling costs by using single stroke fonts.  I originally designed my panel in Visio using a modern TrueType font.  However, this font was not supported by the FPD software.  Therefore I chose the rather plain DIN17 single stroke font using the 0.2 mm engraving tool.  I was more than happy with the appearance of the finished panel.
  • Line art, and logos can be imported into FPD as HPGL plotter command files.  I was able to copy-paste my line art logo (conceived by my wife) from Visio into the fabulous Inkscape open source vector graphics editing software, and export it as an HPGL file.  This file was then imported into FPD, where it was only necessary to set the mirroring option to make it render properly.  I chose the 0.4 mm engraving tool for the logo.
  • Front Panel Designer can export the designs into Autocad DXF files or Scalable Vector Graphics (SVG) format files.  After completing the FPD design, I exported it as an SVG file and imported it into Inkscape.  I then created vector art for all the controls, jacks, and knobs, so I could check the appearance and positioning of all the labels.   During this process, I found that a few labels would have been partially obscured by toggle switch trim washers.  I was then able to adjust the size and position of these labels to eliminate the obscurations.  I enjoyed using Inkscape so much that I spent effort than necessary to make nice models of the chicken-head knobs and toggle switches. 
  • FPD allows you to zoom the view as much as you like to make sure the details of features appear the way you want them to.
What the panel looks like in Front Panel Designer.  The FPD design file is here
Front panel as shown by Front Panel Designer
Exported from FPD as SVG, imported into Inkscape, controls added, and rendered as a PDF.  The full resolution pdf is here.
FPD panel imported into Inkscape, controls added
Front Panel Express delivered the finished panel in less than a week.  It was made exactly as designed.
Front panel as delivered
I unfastened the completely wired and functional controls from my DIY panel and transferred them to the engraved panel without incident.  Everything fit perfectly when re-assembled.
Front panel installed with controls