schematic (service notes) for the Roland SDD-320

https://www.synthxl.com/wp-content/uploads/2019/06/Roland-Sdd-320-Service-note.pdf

So as one can see from this document, the SDD-320 was based on a single large PCB (single-sided, no less) which laid flat in the rack case.  Notice that the PCB for the LED level display was also fabricated as part of the main board, which was designed to then be snapped off.  This is "TV technology"!  Lots of components, and lots of obscure components which probably haven't been available since the design was documented in 1979 (SIP IC packages, "2SA/B/C/D" transistors, etc.).

So the BBD-320 may be a work-alike system, but it's surely not very similar in terms of actual circuitry.  I'll have to see if I can muddle my way through the mods on the BBD-320, using only the SDD-320 schematic.

Despite the differences in construction style, I'll note that the SDD-320 could certainly have been designed to fit into a 1U rack box.  The only issue might have been the power transformer: a different one might have been needed (such as toroidal, if nothing else).  If I had an SDD-320 and I wanted to violate its "vintage mojo" and make it into a practical unit for my purposes, I'd transfer its guts into a 1U rack box and locate the transformer outside the box, in its own housing.


Comments

Post a Comment

Popular posts from this blog

overview of the work to be done

Image
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 t...
Read more

modifying the BBD-320 dimension chorus

Image
The Klark Teknik BBD-320 purports to be a more or less faithful clone of the Roland SDD-320.  These are stereo analogue dimension chorus effect units, housed in 2U rack cases.  If you've followed my previous blog writings, you'll be aware that I just recently ran into a disappointing dead end with the TC Electronic 3rd Dimension pedal, which strongly postures itself as a clone of the Boss Dimension-C pedal, while coyly avoiding any explicit claim of such.  The Dimension-C is the Boss pedal-format adaptation of the SDD-320.  The 3rd Dimension has the same peculiar 4-button interface as the Boss unit, and it claims to produce a "motionless" chorus effect.  And after all, it has the word "dimension" in its name!  But, it's not a dimension chorus.  It has only one clock generator and BBD delay line, whereas two are required to produce a bona fide dimension chorus.  The 3rd Dimension is nothing but a standard chorus unit, dressed up like a Dimension-C....
Read more