[sdiy] Roland cascaded SV 4-pole filters?

[Michael Bacich]

On Mar 26, 2006, at 11:47 PM, Oakley Sound wrote:

> At the time I loved the Jupiter 6's looks and sound. Now, I am  
> always disappointed with it. And I think its the filters that let  
> it down.

The JP-6 Lowpass is pretty weak (especially compared to the JP-8  
Lowpass), but the Highpass and Bandpass modes sound really great, in  
my opinion.  The resonance can easily get out of control. though --  
and not necessarily in a good way.

I wish the JP-6 filter schematic was a little easier to follow.  That  
weird mode switching circuit and the hybrid sub-circuit modules make  
the whole thing kind of confusing, at least the way it's drawn in the  
service manual.  It doesn't help that the filter chips are just shown  
as black boxes, with no graphical depiction of internal functionality  
or pin function.  I need to take the time sometime to draw it out in  
a more straightforward, logical, signal-flow depicting manner.

I bought a brand new Jupiter 6 in 1982 because it was the only synth  
out of the ones I was looking at that had MIDI.  Somehow, I sensed  
that the whole MIDI thing might be kind of important, although I  
wasn't quite sure why -- not yet, at least.  It was a lot of money at  
the time -- more than $2000US -- and I was not rich, so it was a  
really big decision.  The other contenders for me at the time were:   
OB-8, Prophet V, and Jupiter 8.  Yes, yes, I know.  I made the wrong  
choice.  Mea culpa.  I made up for it by replacing it with an MKS-80  
Super Jupiter in 1984.  I loved the MKS-80, but I missed the JP-6  
bandpass and highpass filters, nevertheless.  There's probably an  
Aesop Fable in there, somewhere.  "The Tortoise, the Hare, and the  
Vaguely Dissatisfied Synthesist", or something like that

Mike B.


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