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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Mon Jun 08, 2009 11:56 am Post subject:
Simple lpf filter |
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Hello community!
are looking for a schematics of a simple filter to be added to an atari punk console and other generators.
have to recommend a scheme?
tnx
francesco |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
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Posted: Mon Jun 08, 2009 1:51 pm Post subject:
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I would suggest the filter from Ray Wilson's Weird Sound Generator. It is really simple, has a low parts count, is single supply (you can run it off of the same battery as your APC) and uses very common parts. For a simple filter it works great. The schematic is at musicfromouterspace.com.
If you want something with a little more "punch" and don't mind a bipolar supply, a Sallen-Key filter like Squarewaveparade's sounds pretty good to my ear. His schematic is around here somewhere, but you can also google "sallen-key" and come up with workable schematics...
Do a search on the forum here, there are at least three or four filters which I think can be breadboarded or put together by a relative beginner.
Good luck, hope this helps. |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Mon Jun 08, 2009 3:21 pm Post subject:
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Hi Comrade_zero tnx for reply.
Sellen-key seems to be a good start but the schemathics that i found don't indicate the values on components ...
i found this http://www.daycounter.com/Filters/Sallen-Key-LP-Calculator.phtml
But I do not know how to use it to find the right values and I do not see the knobs in the schemes.
some idea?
MFOS filter is great, I have to try to understand how to extrapolate from original scheme ... there a design ready? |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
Audio files: 4
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Posted: Tue Jun 09, 2009 9:20 am Post subject:
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http://www.musicfromouterspace.com/analogsynth/YOUR_FIRST_SYNTH/WSG_Reborn/WEIRDSOUNDGENERATORREBORN.php?page=WSG
O.k., so the filter section (labeled ODD) is everthing from C1 (the 0.1 uf capacitor) to the right. It is built around the 741 op-amp (labelled U2 LM741 in the schem). If you put together everything from C1 through the end of the circuit (output) you should be good. Just run your output from the apc (or other source) into C1.
(full disclosure: I have built the filter from the original wsg, not the current revision, but I am assuming it should still work.)
As for the Sallen-Key, let me check what I've got on my breadboard, I may be able to post a simple schematic in the next couple of days. In the meantime, you might try Nicolas's state-variable lowpass from the links at the top of this page. It looks pretty simple and has a perfboard layout as well as schematic...
Good luck, hope this helps.[/url] |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Tue Jun 09, 2009 12:02 pm Post subject:
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Fantastic!
expect the results of your tests and I buy the material to test the filter of WSG
thanks |
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v-un-v
Janitor
Joined: May 16, 2005 Posts: 8933 Location: Birmingham, England, UK
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Posted: Tue Jun 09, 2009 12:09 pm Post subject:
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Have you checked out Nicolas' excellent little circuits yet?
http://electro-music.com/forum/topic-34550.html
_________________ ACHTUNG!
ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
DAS KOMPUTERMASCHINE IST NICHT FÜR DER GEFINGERPOKEN UND MITTENGRABEN! ODERWISE IST EASY TO SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKSEN.
IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN. |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
Audio files: 4
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Posted: Thu Jun 11, 2009 1:05 pm Post subject:
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well, I finished my schematic with appropriate component values. I'm attempting to attach it in this post. (I'm not so net savvy, so I type this, post it, see what happens, and if I flub it I'll edit and try again...)
The funny looking pot on the left is a dual (stereo) 100k pot (which will control cutoff). The points are labelled and should be connected to the corresponding points in the circuit.
The resonance pot shown is 100k. It will start oscillating at about 50%, this can be very unpleasant. You can use a 50k here and it will cut before self-oscillating. I like the 100k better because you can get squelchier highs out of it.
Please note this is not set up for voltage control, you have to physically play with the two pots to get sweeps.
I take no credit for the design of this circuit, it is culled from a couple of public sources, however, if there are errors they are my own.
Please note that the points labelled "C" and "Y" on the dual pot must be connected.
Anyway, have fun with this one, to me it sounds great, especially for how simple it is.
good luck.
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Thu Jun 11, 2009 4:14 pm Post subject:
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comrad_zero this schematic is funny! I try it soon.
play with pots is my mission!
can I post it on my site?
Tnx a lot
Francesco! |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
Audio files: 4
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Thu Jun 18, 2009 4:56 pm Post subject:
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impressive sounds!
next week i'm in vacancy... i have a list full of things to do! |
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stolenfat
Joined: Apr 17, 2008 Posts: 476 Location: Sunny Oakland California
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stolenfat
Joined: Apr 17, 2008 Posts: 476 Location: Sunny Oakland California
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Mon Jun 29, 2009 6:28 am Post subject:
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A question for Comrade_zero
I found the time to test your circuit on a breadboard but does not work ...
I have a doubt about the connection of the dual potentiometer.
scheme seems that items B Y and Z are connected together ...
But in doing so how do you work? |
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RF
Joined: Mar 23, 2007 Posts: 1502 Location: Northern Minnesota, USA
Audio files: 28
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Posted: Mon Jun 29, 2009 8:50 am Post subject:
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Looks as if he has a jumper drawn between Y and C of the dual pot, doesn't it? Or you could just use a 200k....
bruce _________________ www.sdiy.org/rfeng
"I want to make these sounds that go wooo-wooo-ah-woo-woo.”
(Herb Deutsch to Bob Moog ~1963) |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Mon Jun 29, 2009 9:48 am Post subject:
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yes, but I have the impression that connected as I understand the scheme, are all linked together ... |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
Audio files: 54
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Posted: Mon Jun 29, 2009 10:09 am Post subject:
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urbanspaceman wrote: | yes, but I have the impression that connected as I understand the scheme, are all linked together ... |
You are correct -- the schematic is drawn incorrectly. B, Y and Z are not connected together. They are connected to the corresponding points on the dual pot.
Ian |
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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Posted: Mon Jun 29, 2009 10:13 am Post subject:
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RF wrote: | Looks as if he has a jumper drawn between Y and C of the dual pot, doesn't it? Or you could just use a 200k.... |
Hmmm ... wouldn't you want to tune both RC's?
Ian |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Mon Jun 29, 2009 10:34 am Post subject:
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tnx Frijitz, i try tomorrow |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
Audio files: 4
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Posted: Mon Jun 29, 2009 1:52 pm Post subject:
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heheh, sorry for the confusion. I mentioned the wiring of the dual gave me trouble...
1) yes, you need a dual pot, not just double the value. The Sallen-Key topology depends on two equal resistors, the dual pot in this case serves that purpose.
2) yes, the schematic is wrong, sorry for that. ERASE THE LINE CONNECTING "B" and "Y". Also ERASE THE LINE CONNECTING "Y" and "Z".
remeber, though, Y connects to two places, it is jumpered to point C of the dual, and it also is connected to Capacitor 1.
I'll try to get a corrected schematic drawn to replace the faulty one. Sorry for the inconvenience, and thank you for giving this circuit a go.
c_z |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Tue Jun 30, 2009 5:02 am Post subject:
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ok, now seems to work...
but the sound is heavy distorted...
I played a bit with the capacitors ...
Ceramic is right? (not electrolytic)
the resistors are in place and IC is a UA741CN
on capacitors says k5m 104 (small orange)
it's all right? |
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
Audio files: 4
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Posted: Tue Jun 30, 2009 9:35 am Post subject:
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I'm glad your getting sound out of it. Try changing your capacitors to 0.01uf ceramic disc capacitors. They should be labelled "103." Hopefully that will clean up the sound a bit.
The volume of your input signal can also affect the amount of distortion.
Keep us posted.
Good luck, I hope this helps. |
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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Posted: Wed Jul 01, 2009 7:25 am Post subject:
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this is my first design regard the pcb. I hope goes well, I have not yet tried.
I would have some opinion from you.
thanks
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urbanspaceman
Joined: Feb 26, 2008 Posts: 77 Location: italy
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comrade_zero
Joined: Mar 05, 2009 Posts: 66 Location: arizona
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Posted: Wed Jul 01, 2009 11:15 am Post subject:
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WOW, that redrawn schematic looks great!
Have you gotten a better sound or is it still distorting heavily? Some sound samples once it's finished are always welcome.
I'm a real beginner, I've never done any PCB's, just breadboard/ verobard type stuff, maybe someone here with more experience can give you some good feedback. Let us know how it goes.
cheers,
c_z |
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Tim Servo
Joined: Jul 16, 2006 Posts: 924 Location: Silicon Valley
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Posted: Wed Jul 01, 2009 1:01 pm Post subject:
Simple lpf filter Subject description: A few minor suggestions |
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Hi Urban,
Not bad for your first attempt at laying out a PCB. If you don't mind, I'll offer a couple of hints and suggestions:
1) Label the positive Output terminal as "Out" and the ground as GND. The plus symbol that's there now is a little confusing, especially since it's close to a power input pad. Same thing with the Input terminal - label it as "In" rather than "+" and label the Ground terminal as GND.
2) Play with the layout a bit and see if you can't get the Y, B and Z terminals all next to each other. Same thing with the P1a, P1b and P1c terminals for the Resonance pot. This will make the wiring cleaner and easier. One routing trick you can try is to run a trace under a resistor or capacitor, esentially using them as 'jumpers.'
3) Make your traces and pads fatter. Easier to solder and easier to etch if you do your own boards.
4) Definitely make the power traces fatter. Reroute them and put them together if possible. Generally, you should route the power traces first (even though they're really short on this board). I try to get all of my connectors to the edges of the board, and keep connectors grouped together where it makes sense.
Hope this helps!
Tim (laying out a PCB as we speak) Servo |
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