MOTM

At 7:35 PM +0100 12/18/01, jhaible@... wrote:
>
>>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.

I completely agree, and I would say that all of them do not have "that
Roland Sound", unless you want to make the silly semantic argument that
everything Roland has a Roland sound.

>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.

It's more than unlikely that it shares this secret with all other Rolands
-- I think it's downright impossible.  However, the IR1309 might have a
unique quality which is responsible for a special sound.  In fact, it's is
very likely.  The question is: is it different enough to make a "clone"
worthwhile??  I can't answer that question.  Yet, if you would like to try,
I have an IR3109 chip, and Juno 60, MKS-80, SH-101, and MC-202 schematics
that I can send you.