overview of the work to be done

So my main modification to the BBD-320, as with any of these dimension chorus units, will have to be adding depth and rate pots.  Given that there's more space available than in the pedal units, I think I will preserve the mode buttons, and just provide a toggle switch to enable either the buttons, or the pots.

However, I can't get over my dislike of how big the box is (2U rack unit).  This is more space than I want to devote to a single effect like this in any of my future guitar rig scenarios.  My McGrath Stereo amplifier design will probably provide some extra rack space within the case design, for digital reverbs or for effects like this, but I was really only planning to provide 1U of space, which is enough for most relevant effects.  1U has become the de facto standard for almost all modern effects units.

Looking at pictures of the inside of the BBD-320, I can see that the box is mostly empty.  There are PCBs mounted to the front panel, and a PCB mounted to the back panel, all apparently less than 1U deep, and the rest is empty space.  Perhaps the original Roland unit had a lot more circuitry inside?  Clearly, Klark Teknik could have fit their circuitry into 1U, but they chose not to, simply to retain a visual similarity to the Roland original.

So another possible mod of the unit would be to strip out all the boards, and fit them into a new 1U rack case.  This would be quite doable, although a number of items such as the jacks and power connector on the back, and the LED level meter on the front, would have to be separated from their PCBs and mounted to the panels separately, with wires connecting them to the PCBs.

Also, I have mused about the possibility of building a dimension chorus with vacuum tube audio stages.  The BBD-320 might be the ideal platform to support such a project, with an external tube board jumpered in to replace the several audio opamps.  Of course, a project like this would be easier to accomodate in the voluminous space available in the 2U rack box; but probably I would still want to fit it into a 1U rack case.  It's not clear that there would be any overwhelming benefit to using tubes in place of the opamps in this circuit, especially because I'd probably still continue to use the NE570 compandors, which contain solid-state opamps internally; this would be more for the "psychological" benefit of running audio though tubes.  As such, it might be a desirable product to sell, although of course I wouldn't be able to sell units based on the guts of the Klark Teknik circuit.  Anyway, for the forseeable future, I think I'm content just to get a solid-state version of dimension chorus operational.