[sdiy] Book on analogue filter design

[Richard Atkinson]

Hi Colin,

I was thinking something along those lines, except instead of
desoldering the whole lot, I would leave the the IR3109s and possibly
RA11 (a resistor array which seems to be in the same arrangement on
both designs) and desolder all the other parts - IC47, RA12, RA13,
RA14, various resistors and capacitors - and see if the cascaded
integrator design could be fitted onto the rest of the original
circuit board using the empty through-holes and some careful track
cutting.

It may be possible to leave IC47 in situ as well, and use the existing
HPF/BPF/LPF select signals to select between 12dB and 24dB LPF.

Richard


>
> Th JP6 filter is a pair of SVFs in series, built from Roland IR3109 ICs.
> You could extract these chips, plus a few other components around them, and
> replace them with a header connection to give you the necessary filter
> cutoff and resonance CVs, audio in and out, filter mode select and power
> connections.
> Then design a little daughterboard to re-use your IR3109s in the cascaded
> integrator design used in the JP8.
> It'll be very tricky to do this in a way that allows you to close the lid on
> the JP6 though.
> Doing it all 6 times is going to be a lot of work.
> I was planning to do this with my JP6, but I bought a JP8 and sold the 6
> instead - which was much easier.
>
> Cheers,
> Colin f
>
>
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