Joined: Jun 26, 2009 Posts: 226 Location: The Darkside
Posted: Thu Feb 10, 2011 5:42 pm Post subject:
textual wrote:
I am runnig mine of 9V, works fine.
The CV / vactrol is controlling cut off. I don't see why you can't connect it to dual gang pot and be fine.
I am also only using 1 stage of an op-amp. I built 4 of these (now filters with 1 quad op-amp.
Are you sure this will run off a single 9v supply?
Doesn't it need a voltage divider?
I have this on breadboard and it just doesn't sound right, output is too low, plus the res pot doesn't do a thing.
When I remove ground from pin 4 the output goes way up.
Using a TL081 for now
Joined: Aug 08, 2011 Posts: 192 Location: Gig Harbor
Posted: Mon Sep 05, 2011 1:47 pm Post subject:
I don't mean to commit topic necromancy (RISE ONCE AGAIN MUAHAHAHH!!) but since my question is related to this thread - the last inverter VCF cricuit posted - can it be cut down to just HPF/LPF by lets say cut out the bandpass part, or is the bandpass stage necessary to create the lowpass output? Perhaps kill the LP stage and just do a HP/BP combo?
I managed to put togetter a 4049 based vco with adjustable tri/saw (I think) output and have to inverters left for uh.. something like a VCF. Any suggestions?
I like this thread. It's like that old sketch from Saturday Night Live: "active filters - talk amongst yourselves"
For me, filters are one of the easiest ways to sculpt that buzzy, glitchy square wave into something even weirder. And filters are one more opportunity to use LDRs, LFOs, etc. Lots of expression possibilities! _________________ "The life of a repo man is always intense."
i'm going to try building a 4069 filter stand-alone. Probably only LP, but maybe HP also. i have a 40106 drone synth that i built a WSG filter into - it sounds fine but i'd like something more versatile and with a sharper cutoff freq. I think i'm going to try breadboarding one off the last one Silesius posted (http://i42.photobucket.com/albums/e340/Silesius/FILTER.png). If it turns out well maybe I'll replace the WSG filter in my 40106.
Seems like the conclusion was to do something along the lines of 10k VR for a input/attenuator and use a 20k VR for R3 for res?
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
Posted: Sat Jun 09, 2012 5:24 am Post subject:
I assume all those cap values are in microfarads? So that's 1nF caps used in with that op amp? _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Jeeze. I had no idea decimal point cap values had become arcane.
.1uF=100nF
.01uF=10nF
.001uF=1nF
Cultural thing ... in the EU the n prefix seems to be used more ... also in the form of 2n2 for 2.2 nF ... and in the US you'll more often see .001 µF, or indeed just .001. _________________ Jan
also .. could someone please turn down the thermostat a bit.
Joined: Nov 16, 2007 Posts: 37 Location: Gig Harbor
Posted: Wed Nov 07, 2012 10:26 am Post subject:
Well since it hasn't been that long since my last reply on this thread - I'm trying to get back at experimenting with electronics and I wonder if anybody has successfully put together an active resonant RC-ONLY vcf? by RC only I mean only resistors and capacitors, no transistors, op-amps, inverters or any semiconductors of any kind - requirements would be acceptable response, more or less decent resonance, and an acceptable range for resonance and cutoff control. Is it even possible and practical to do something like that?
Well since it hasn't been that long since my last reply on this thread - I'm trying to get back at experimenting with electronics and I wonder if anybody has successfully put together an active resonant RC-ONLY vcf? by RC only I mean only resistors and capacitors, no transistors, op-amps, inverters or any semiconductors of any kind - requirements would be acceptable response, more or less decent resonance, and an acceptable range for resonance and cutoff control. Is it even possible and practical to do something like that?
That wouldn't be an active filter, then. It would be a passive one. i imagine you would have a pretty hard time making a resonant filter with only caps and resistors.
Joined: Nov 16, 2007 Posts: 37 Location: Gig Harbor
Posted: Thu Nov 08, 2012 12:56 am Post subject:
Thanks for the swift and clear answer! Now if only somebody would answer my question about the Paia LPF that I posted in the diy forum, hint, hint, point, point
Well since it hasn't been that long since my last reply on this thread - I'm trying to get back at experimenting with electronics and I wonder if anybody has successfully put together an active resonant RC-ONLY vcf? by RC only I mean only resistors and capacitors, no transistors, op-amps, inverters or any semiconductors of any kind - requirements would be acceptable response, more or less decent resonance, and an acceptable range for resonance and cutoff control. Is it even possible and practical to do something like that?
Yes. Not 24 db/octave... but could be tweaked...
What about connecting a small speaker to your output and sticking it into your mouth. You could move your jaw, change the shape of your mouth cavity and vary the hole made by your lips. ***UNVERIFIED*** (may want to test with small headphone speaker, earbuds etc.)
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
Posted: Thu Nov 29, 2012 12:12 pm Post subject:
Thats not really practical, talk boxes use a hose to separate the electronic parts and the mouth of the user. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Too elaborate. Place a large funnel over a small speaker. Fasten a suitably sized hose on the small end of the funnel, stick the other end of the hose in yer pie-hole et voila -- talk box.
(Somewhere there's a recording of me vocalizing I Am The Walrus this way.) _________________ Revenge is a dish best served with a fork... to the eye Last edited by richardc64 on Thu Nov 29, 2012 4:36 pm; edited 1 time in total
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
Posted: Thu Nov 29, 2012 4:13 pm Post subject:
richardc64 wrote:
(Somewhere there's a recording of me vocalizing I Am The Walrus this way.)
Fuck, I was going to sleep, but now ... I must find it!!! _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
I will bring this topic back from the dead because I built a nice little vcf, which sounds very dirty and gritty. It is not crazy resonant, but just resonant enough. I started messing around with this circuit when I breadboarded the moduletta vcf last year.
Dirt VCLPF is a very simple inverting twin t filter with a drive/gain stage. You can Ignore the lower part, it is just my power supply. Just connect VCC with 9V or 12V and it will run fine. Maybe put some filter caps between VCC and GND, because this filter is very sensitive to shitty wallwarts which will introduce some noise to the output signal.
DirtVCLPF.png
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R16 is a 20/50K trimmer to limit the lowest cut off frequency
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dirtvcf_01.mp3
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Dirt VCLPF, Yamaha QY70, two LFOs and a LOWPASS GATE..
Bravo, looks like an easy build, one for the breadboard list, you can never have enough filters
Alfa has been making affordable clones of old synth ICs, including the 3320VCF. Electric Druid and Small Bear sell them, most likely others do, too. They sound great and are simple to set up (needs bipolar DC but I've made them work just fine on +/-9V using an LT1054 as a voltage inverter). _________________ "The life of a repo man is always intense."
it is an easy build indeed, if you skip the drive stage it gets even easier.
Speaking off ics... I just found out that the SSI2144, which is the clone of the legendary SSM2044, can run off 9V (-4/+4V minimum voltage).
I have also a multimode VCF (LP/HP/BP/NOTCH) in the queue and I will share the schematics the next months. It is a weird combination of an Oberheim SEM VCF and a WASP VCF.
vclpf.PNG
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This is a render from my VCLPF PCB.
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