Exploring other filter modes with the 4PM filter

I am really loving the 4PM filter. It is very flexible, and is even very useful when using the other filter modes!
I really dug in to what is possible when using the other filter modes with the wrong hardware. The best one to use was the SVF mode as the second filter mode setting can completely change the timbre. Of course the secondary cutoff and resonance have no effect. There is also a bit of oscillator leak when the filter is fully closed, but that is what a volume envelope is for. The resonance can be anywhere from calm to overdriven depending on the two filter modes selected. I would honestly consider the SVF a whole extra set of 4PM filter options.

The SMR4, SSM, and DSP filters all have a very similar character. They sound distorted and slightly bit crushed, but they only work as a low pass filter. My personal favorite was the SSM because the resonance goes really crazy with that mode.

The LP2 + DLY is unique because the feedback/level controls the amount of resonance. This provides some interesting movement when you fade high resonance into a sequence.

The PVK and SP filter modes also have similar characters. The PVK can sound cleaner depending on how the overdrive and FM are set.

One thing I did notice with all filter modes is that using the bandpass filter modes gave a more authentic low pass sound than the low pass filter setting. That was interesting to learn. Needless to say, I have not mapped what everything does yet, and lots of setting sound bad. High resonance and cutoff settings tend to give very thin and digital results in most instances. That is not a bad thing if you want that sound though.

I was able to get several great timbres, but there is no way to save these settings with the patch, so I will have to write them down. I also do not think that saving the filter mode with the patch would be a good use of the remaining space as most Shruthi users will have no use for this.

Also, I love the addition of being able to trigger the envelopes from the mod matrix! I have made a few self-playing patches like this. That combined with the sequencer per patch is a great reason to upgrade. Now the Shruthi really is a modular in a box!

Hmmmm these are not “other filter modes”, these are more like “sending total garbage into the digital switching section of the 4PM board”. I’d say we’re more in circuit-bending territories here :slight_smile:

There shouldn’t be any difference between “LP” and “SSM” - the “SSM” setting just displays a menu with the HPF setting (which does absolutely nothing on the 4PM board). In both cases, you’re shifting out at a random sample rate the 8 bits of the LEDs unto the filter mode control register on the 4PM board, so everything is sounding bit-crushed, random, and it depends on which LEDs are on.

Note that I cannot guarantee that this won’t do any damage to the filter board.

Ah, I initially thought @audiohoarder had six or seven different filter boards connected to a single Shruthi control board via some form of switch, but it seems not.

I am using the SVF setting with my three-storey Shruthi (two SMR4mk2 filter boards), which allows convenient control of both LP filters, but of course the digital switching signals can’t do any harm in this case because the SMR4mk2 boards aren’t connected to them.

This can actually sound useful compared to the average circuit bend. :slight_smile:

The different LEDs may have been the difference, but I will have to check again to be sure. Yes, the HPF did nothing.

I don’t see this being too detrimental to the filter. I do appreciate the warning. If the voltages exceeded the maximum limit, I would be worried, but there were no components getting hotter than usual. I can easy check this as It is just sitting in a plastic container waiting for a proper case. I would not be surprised if the life of the electrolytic caps were shortened.

@BennelongBicyclist: Nope, I am just using the 4PM and using the “wrong” filter setting. Then messing around to see if anything is useful. I do not recommend doing this, but I figured “why not?”