[sdiy] initial roland IR3109 vcf parts study results

[Dan Snazelle]

just thought i would let people know what i have found so far

this is just what i have figured out from looking at a lot of the service manuals

BUT just from looking at various roland schematics
which all use the IR3109 chip, i have found a few interesting things. keep in mind,
this is the one roland chip which seems like it would be easy to at least
Learn from if not completely clone. from this list, it definitely seems like the IR3109 chip was used differently in different models to give a different signature sound. I am going to of course going to try and experimentally apply this and see if i can work out a good filter or 2!! any comments appreciated!

OK here you go

looking at the TYPE (only) of resistors and caps used in classic roland synths:

IR3109 VCF configuration in different Roland Synth Models (may have errors)

Jupiter 4:

560 ohm x 4
100k x 7
470pf x4

jupiter 6:

unknown resistor arrays for resistors
330pf caps

* due to cap values, may be same resistor values as JX3p

jupiter 8:

68k x7
560 ohm x4
240pf x4

*sAME PARTS AS JUNO 6

sh101:

560r x4
68k x7
240pf x4
uses diodes in resonance path

JX3p:

68k x7
560r x4
330pf x4


Ok that is all i got for now. there may be other roland synths that use
this chip but i dont have the schematics!

also..i will try to put together values for all the old
NON SPECIAL FILTER CHIP roland synth OTA filters.

this is of course disregarding right now how the OTA's are configured.

(only been at this for one day so far so....)


hope this is at least interesting!!!

thanks