SVF Filter specific question

Hi dear ones!

I’m still tuning up the shruthis and it did take me a long time (several weeks) to get my head around the filter functions of the SVF filter board. “md2” - “+lp, +bp, +hp” stand for “parallel mode” which acts like a second internal audio path, thus boosts up the signal by several (3? 6?) dB once in full swing …
Next up “md2” - “>lp, >bp, >hp”, self explanatory really stand for “series mode”, so one after the other with no audio boost and no audio out if one cuts off completely.

So, what does “md1” - “lp<, bp<, hp<” stand for? anyone? feature documented?


Yes, for the second filter + is parallel (filter 2 receives the same input as filter 1, and both filters are added and sent to the output) and > is series (filter 1 out sent into filter 2 input).

For the first filter, “<” means cutoff coupling. In this mode, it simply means that filter cutoff 2 is now relative to filter cutoff 1. So when cutoff2 = 64, both filters are at the same frequency set by cutoff 1. When cutoff2 = 65, filter 2 is always 1 semitone higher than cutoff 1. cutoff = 63 and it is one semitone lower… And so on!

This is a new, undocumented feature from the latest firmware revision.

I get it and I like it! Cool that you add on features later. SVF is a fun filter, have to dive in more … and upload SVF exclusive patches.

I have a lot of low pass filters, do you guys recommend the SVF or SDE SMR-4 for some high pass action?

I have the SVF and absolutely LOVE it! The big difference between the SVF and SMR is the SMR is 1 24dB filter and the SVF is 2 12dB filters. Way more modulation possibities. I suggest getting the SVF but still do the SDE mod. Can never have enough Shruthi’s.

Is there anybody who did the SDE mods for the dual SVF? I’d like to make a sidekick with dual SDE SVF.

I don’t think some of the SDE mods would translate that easily to the SVF filter structure.

Do you think the input distortions will work? Values of the resistor would need to change of course. And the resonance flavors? Isn’t the SVF circuit a little bit similar to the 4PM for the resonance flavor?
The filter modes are not necessary because they are already there. And the output distortion should work.

Hmmm there is only one input amp stage for both filters that might be a problem… well it will be an experiment! :slight_smile:

I was half asleep when I wrote that. I meant get the SVF and do the SDE mods to an SMRMKII.

I’m about to publish the SDE Filter Flavours MkII, so I’ll take a look at the SVF circuit and see what I think of the possibilities.

The main difference I suspect will be that internal signal levels will be different, so whether ot works or not the flavours will move away from their carefully selected sweet spots and become stronger or weaker.


OK - at the flavours point in the SVF circuit signal levels look to be exactly twice those of the original SMR4-MkII, and therefore three times the reduced levels of my SDE MkII flavours with squelchy IR3190 resonance.

So, I’m afraid you’re on your own with adding to the SVF, although you could try the MkI flavour circuitry but doubling up on the number of diodes (i.e. use two 1N4148 in series instead of one). Sorry!

Output drive will work fine though!


Thanks this is al ready lot of info to start out with!