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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Simple active filters?
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acidblue



Joined: Jun 26, 2009
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PostPosted: Thu Feb 10, 2011 5:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

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 Cool 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
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patrickvf1976



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PostPosted: Mon Sep 05, 2011 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

I don't mean to commit topic necromancy (RISE ONCE AGAIN MUAHAHAHH!!) Razz 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?
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Cynosure
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PostPosted: Thu Sep 08, 2011 5:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

Lots of great simple ideas here for me to try. Thanks!
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garcho



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PostPosted: Thu Jan 26, 2012 4:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

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!

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Lysol



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PostPosted: Fri May 18, 2012 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

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?
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kaputtpanzer



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PostPosted: Mon May 21, 2012 7:22 am    Post subject: Reply with quote  Mark this post and the followings unread

I made a good sounding filter for use with cmos and 9V batteries. It's based on the wsg/dronelab filter and it has a hp/lp mix pot.

I think it is possible to replace the 4,5V connection, at the non-inverting pin, by a CV input.


9vHP_LPfilter.png
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9v_filter.mp3
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The input signals for the filter are 4 squarewave oscs feed into 2 XOR gates.

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garcho



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PostPosted: Wed Jun 06, 2012 10:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Kaputtpanzer, I'm going to breadboard this soon!
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richardc64



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PostPosted: Fri Jun 08, 2012 2:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's one I like a lot.

The 4069 version could have a Q Resonance pot and HP/BP inputs like the 324 version. Play with the cap values.


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JingleJoe



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PostPosted: Sat Jun 09, 2012 5:24 am    Post subject: Reply with quote  Mark this post and the followings unread

I assume all those cap values are in microfarads? So that's 1nF caps used in with that op amp?
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textual



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PostPosted: Sat Jun 09, 2012 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
I assume all those cap values are in microfarads? So that's 1nF caps used in with that op amp?


pretty sure those are 1n, Joe

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richardc64



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PostPosted: Sat Jun 09, 2012 10:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Jeeze. I had no idea decimal point cap values had become arcane.

.1uF=100nF
.01uF=10nF
.001uF=1nF

Here's some short samples of the 324 filter with white noise as input. Caps were 560pF and feedback R was fixed 680K.


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Almost Cymbal. Needs metal.

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handclap?

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Closed HiHat

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Blue Hell
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PostPosted: Sat Jun 09, 2012 11:02 am    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
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.

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lostinpurdy



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PostPosted: Wed Nov 07, 2012 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

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?
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Psyingo



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PostPosted: Wed Nov 07, 2012 11:48 am    Post subject: Reply with quote  Mark this post and the followings unread

lostinpurdy wrote:
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.
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garcho



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PostPosted: Wed Nov 07, 2012 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Is it even possible and practical to do something like that?


no and definitely no

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lostinpurdy



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PostPosted: Thu Nov 08, 2012 12:56 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Wink
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-minus-



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PostPosted: Mon Nov 12, 2012 10:53 am    Post subject: Reply with quote  Mark this post and the followings unread

lostinpurdy wrote:
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.)
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JingleJoe



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PostPosted: Thu Nov 29, 2012 12:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thats not really practical, talk boxes use a hose to separate the electronic parts and the mouth of the user.
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richardc64



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PostPosted: Thu Nov 29, 2012 12:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://alexplorer.net/guitar/projects/talkbox.html

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.)

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Last edited by richardc64 on Thu Nov 29, 2012 4:36 pm; edited 1 time in total
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JingleJoe



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PostPosted: Thu Nov 29, 2012 4:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

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!!!

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JingleJoe



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PostPosted: Thu Nov 29, 2012 4:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

nope all I can find is this ... almost as good. Shocked Laughing


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richardc64



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PostPosted: Thu Nov 29, 2012 4:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
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!!!


Sorry. I should have said "Somewhere in my dozens of old tapes..."


Can't see the vid scratch [/i]

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