[sdiy] help finding roland filter schematics?

[ChristianH]

Maybe the original circuit was abandoned before the service manual was
completed, and the revised circuit was still published under the same
model name. 
It could then have been decided that the actual synths produced were to
include the A, because a number of original instruments had already been
shipped (and maybe to convince Moog that all those later models indeed
had the revised circuit).

speculations, all those speculations...
Chris



On Wed, 06 May 2009 16:06:35 +0200 Florian Anwander
<fanwander at mnet-online.de> wrote:

> Hello Louis
> 
> Thank you for the hint. This seems to be wrong indeed. The 
> servicemanual, where it is taken from says clearly "SH3" on its 
> frontpage - I always overlooked that and took for an SH3A manual.
> 
> If this diode ladder filter is an SH3, all the rumours on patent 
> infringements in the SH3 (which shall have caused the change to SH3A) 
> would be false. Now: why did roland change the filter design?
> 
> Florian
> 
> > What I find interesting in the link below is that it lists the SH-3A 
> > filter as
> > a diode ladder (and even includes a schematic for that), when the SH-3A 
> > actually
> > has a transistor ladder.  It's clearly a traditional Moog transistor 
> > ladder in
> > the Service Notes, which I have verified against the actual SH-3A I have 
> > here.
> > 
> > And the Service Notes list the transistor ladder in all revisions, so 
> > Roland aren't
> > hiding it in any way.  Not sure where the diode-ladder versions comes 
> > from, but
> > I'm sure it's not the SH-3A.