[sdiy] Modding the MKS-3(7?)0 - Looking for suggestions

[bayne d'artagnan]

On 10/12/07, . <intent at netpratique.fr> wrote:
> On Friday 12 October 2007 10:57, Colin f wrote:
>
> > JX10 VCF is IR3R05 - a cascaded pair of 12db/oct SVFs.
> > According to the MKS80 service notes, one filter is an LFP, the other a
> > BPF. There is a VCA on there too, so there is no direct output from the
> > filter.
>
> There are too rev of the MKS80, the later (rev5) with the same VCF chip than
> the MKS70.
>
> Does someone have the datasheet of the IR3R05, btw ? How easy it would be to
> neutralize the second stage ? I see 4 same capacitors around the chip, i
> wonder if removing 2 of them would do the trick.. That could'nt be that
> simple.

Yes, it basically is that simple. Replace them with much smaller caps
or just try removing them altogether. You can use analog switches/fets
to do the dirty work and have it switchable if you like. The diagram
for the IR3R05 is in the service manual of almost any synth that uses
it: JX10, MKS50/70, later MKS80.


> As for the older roland synth with IR3109 VCF (MKS30 and early MKS80rev4), one
> advantage is that there is no onboard VCA, so its possible to add some boost
> circuit in between (but the sound is fatter on theses older synths, not sure
> its usefull).

Not to mention the fact that the IR3109 is a MUCH better sounding filter.