MOTM

alt-mode schrieb:
> I'll second this.  The Roland filters have a very unique 
> sound.  Even the variations 
> between the Roland analog products seem to have a basic 
> character of the filter that 
> seems unique to Roland.  I posted a short review awhile 
> back about the two kinds of 
> System 700 filters.  They have a unique sound that is not 
> like any of the current 
> MOTM filters.  
> Paul has mentioned the importance of 
> filters on the character of a 
> synth...  This is another one of those "characters".  Now 
> when folks are talking 
> about Roland filters, they usually mean the TB-303.  I 
> don't know that I would be 
> that specific.  I think there is something to the 
> character of Roland filters that 
> applies to all of them.  That would be the "essence" that 
> MOTM should be look

Let me offer a slightly different conclusion:

We have a variety of filters from Roland, OTA filters with
opamp buffers, OTA filters with FET buffers, Transistor ladder
filters, Diode ladder filters, integrated quad OTA / quad buffer
filters, and they *all* have "that Roland Sound"! If this is
true (and I'm not the one to decide this), then you definitely have
to look for an important factor which contributes to "that Roland 
Sound", *other* than the filter circuit.

It may be other parts of the signal chain: VCO, VCA, fixed HPFs
from AC coupling, fixed LPFs from bandwidth limiting, the opamps
they used, and so on. It may be the choice of input and output
level of a filter. In the Juno6, you have ONE oscillator going
into the VCF at a FIXED level. A self oscillating filter output
will go into the VCA at a FIXED level. In a single-VCO 
configuration, it's even hard to tell distortion (VCF or VCA
overdrive) from the linear filter function, because there is no
2nd VCO to change the degree of distortion.
These are just examples for things that can easily have an influence
of what is perceived as the "character" of an instrument, or even
as the character of a family of instruments from the same
manufacturer. (And this has *nothing* to do with the VCF circuit 
that is used !)

Let me make this clear: *Maybe* the Roland filter chip, which has a 
very 
similar block structure as the SSM2040, has some yet unknown feature
which is responsible for a special sound. It's not entirely impossible:
Before I learned of the SSM2040's internal circuit, I also thought
"just another ota filter". So it's *possible* that the Roland chip
holds a similar (but different) secret. But is it *likely* ? I think
it's *unlikely* that it has a secret which it also *shares* with all 
the other (discrete and disclosed) Roland filter circuits.  

JH.