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SV Filter PRC3A as oscillator - from sine to chaos
MUFF WIGGLER Forum Index -> BugBrand Devices  
Author SV Filter PRC3A as oscillator - from sine to chaos
otoskope
We're all hailing the bug SV Filter as a great module - to be pinged for nice percussion, as a smooth multimode filter, etc. Sometimes people complain that it is not self-oscillating. I did a little investigation of how to make it generate various waveforms, and I was surprised. It can generate a vast variety of waveforms, all by itself, with just a couple of feedback chords.

A few general comments:
* All waves are generated by a single SV Filter module going directly to output/oscilloscope (green banana).
* The photo to the right shows the exact settings rendering the wave to the left.
* The oscilloscope parameters were adjusted to show the wave clearly. Real amplitudes vary, as do the frequencies depicted.
* All these waveforms work over the full audible range, and can be controlled with the 1V/oct input, which was not used for feedback. EDIT: And quite a few of them seem to work well down into LFO range, with the help of negative CV. Some I have gotten down to the 15sec range. That may change the waveform a little bit, though.
* Altering the modulation amounts (Fmod, Qmod) and Q often changes both waveshape and frequency, which could be considered good or bad, depending...
* Running the feedback signals through VCAs would allow some serious waveshape morphing.
* I made no sound examples, as most of you have this module. The pictures show clearly that this is a wavegenerating treasure-trove! Start exploring!

First, some basic waveforms:


One way to make a decent sine.


Another quite pure sine.


A triangle wave, also almost perfect.


Rising saw. I needed some FM to achieve the saws.


Falling saw. This one just flipped two cables compared to the previous one.


Sort of squarish. Certainly sounds like one.
EDIT: This was actually a pretty good square, until it was plugged into the output mixer module, which somehow distorted the negative part a little.

Over to some stranger waves:


A folded sine. No FM used!


A weird one.


The previous one, but with FM added, and some more Q. Makes the peaks sharper.


Adding Q modulation gives interesting hi-freq pulses on the waves. Not unrelated to Metasonix weird pulser circuits.


Some more intense pulsing.


This one is unstable, altering between the two depicted shapes. Interesting.


Some hard FM to create sharp peaks.


More FM. The very sharp impulse on this one contains very high partials.


A very simple one, with weak fundamental, nasal sound.
EDIT: Just realized this is actually a softer, slightly rounder version of the folded sine above - with slightly lower Q.


Finally, a few saw-pulse combinations:




Notice that this one alters between two and three saws on each wave.



[EDIT] Added some quadrature and dual waveforms:
(red and green banana)

Quadrature sine, i.e., two sines 90 egrees apart. They don't have equal amplitude when output from the module (adjusted in the oscilloscope), but still...it you're happy with a not-so-pure sine, you can increaase the Q and get less difference in amplitude.


Square and triangle, with quadrature phase difference.


Sine-ish wave and square, 180 degrees out of phase.


Saw and U-wave, in phase.
tIB
Oh my! MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING MY ASS IS BLEEDING hyper hyper hyper hyper hyper
radams
thanks for being here Palle - your extra brain power makes up for the part of mine that has rotted out !
Seriously - your knowledge is a great resource and I appreciate your willingness to explore and share
otoskope
I'm not sure about the extra brain power. But I have no lack of curiosity!
/Palle
otoskope
Added some quadrature and dual wave configurations to the end of the post!
/Palle
jenamu6
Wow It's motherfucking bacon yo applause nanners
darenager
Yeah go Palle!

The SV filter is astonishingly good, and flexible - I have 7 now! And really could do with some more.

Feeding back as you have shown here is a great way of unlocking some really great stuff, stick a VCA between the output being fed back and you have VC feedback. I have not used mine as oscillators aside from being swept for drum stuff, but I have used feedback to change the response of the filter on the Bugphonic stuff with really great results.

Thanks for posting this!

thumbs up

EDIT - I must admit that I actually prefer that it does not really self oscillate, as I find that the trade off is that when being used as a filter it is much more stable and easy to control, and having owned a lot of filters I think I can easily say the PRC3a is easily by far my favourite.
tIB
^ I want 7!
darenager
No Mr Tibbs, you NEED 7 lol
otoskope
I only have 4...poor me. I also need 7, at least!
miditerranean
Very impressive, otoskope! Thanks a lot!
tIB
I reckon I need 5... currently keeping my eye out for a thrid. [/i]
indexofmetals
we're not worthy we're not worthy we're not worthy Palle

time to unpack that Parcel from Tom and get out the extra SVF
a100user
Way to go Palle

I'm off to play thumbs up
indexofmetals
besides more svf (I now have 3) I need an oscilloscope (not sure if I can eve spell it). what would anyone recommend?
otoskope
Added some comments to the waves above, especially one about having modulated some of these waves down well into CV range, down to maybe 15 sec per cycle when I was using a negative CV offset into the V/Oct mod in.

/Palle
oljud
I for one wouldn't mind a super-sfv with all four outputs available at the same time... And extra tasty goodness of course. CV over fm amount, pre gain knob, mix output..?
BugBrand
Sterling work from Palle!

Mega-SVF -- the thought has crossed my mind before, that's for sure..
otoskope
oljud wrote:
I for one wouldn't mind a super-sfv with all four outputs available at the same time... And extra tasty goodness of course. CV over fm amount, pre gain knob, mix output..?


I did think the same thought today, while reading up on the Serge Variable Q Filter, which is very similar, I think, and has a few of those features. But on the other hand - CV control of FM (add a VCA), pre-gain (add a pre-amp), mix output (add a dual DC mixer) are easily available already. Just add another module. I can't really see the point of those features being built in.

But all four outputs at the same time: YES! nanners That would make a big difference. And a switch for hi/low range. You can certainly push this into CV territory.

/Palle
oljud
Yes, I know, I just figured that 2 more outs would push it into 2fw territory anyway so one might as well put in something extra.
tragedybysyntax
Holy crap... can we hear samples? wink

SV Filter has to be the BOMB! Eventually I'll snag one.... or 3!
otoskope
Didn't we just agree that 7 was the recommended dose?
EDIT: No, sorry, I didn't make any samples. That would've been too much work. Took almost a full day to make that series of examples anyway, and when the post was almost ready, my computer went zen... But you'll have one, soon! Then 7...

/Palle
otoskope
tragedybysyntax wrote:
Holy crap... can we hear samples? wink


Yes, now! I just uploaded a sound/video example in a separate thread: https://www.muffwiggler.com/forum/viewtopic.php?t=51704

/Palle
KNYST
Hmm... I messed around with feedback quite a lot when I got my first PRC3A, but didn't find much use for it, part from when running an audio signal through it simultaneously, but I guess I was lazy thumbs up
Never thought about looking for quadrature sines, despite using my Serge equivalent for exactly that d'oh!
Very kind of you to post all those scope grabs and patches!
Tackar.

And this:
Quote:
maybe 15 sec per cycle when I was using a negative CV offset into the V/Oct mod in.
w00t
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