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 Forum index » DIY Hardware and Software » Developers' Corner
looking for schematic of a bandpass filter
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Grumble



Joined: Nov 23, 2015
Posts: 833
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PostPosted: Sun Nov 18, 2018 2:48 pm    Post subject: looking for schematic of a bandpass filter
Subject description: simple to build and with a dual potmeter
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Help!

I'm looking for a bandpass filter where it is possible to shift the center frequency with one dual-potentiometer.
I know there must be some, but I cant fint them...
Power supply: +12volt, -12 volt
Center frequency: 300Hz - 3kHz

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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Sun Nov 18, 2018 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

can't you do that with an arduino ? clown

(sorry, don't have anything for you)

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JovianPyx



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PostPosted: Sun Nov 18, 2018 5:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Why not a BP VCF like a state variable? Then you can have a pot (single) for Fc and another pot (also single) for Q. Then if you need to control it with voltages, you've got the inputs already there.
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Grumble



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PostPosted: Mon Nov 19, 2018 12:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Posted Image, might have been reduced in size. Click Image to view fullscreen.
This might be just what I'm looking for...

Thanks!

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g.gabba



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PostPosted: Mon Nov 19, 2018 1:01 am    Post subject: Reply with quote  Mark this post and the followings unread

lol, u wrote while i was preparing this Smile


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ixtern



Joined: Jun 25, 2018
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Location: Poland

PostPosted: Mon Nov 19, 2018 1:21 am    Post subject: Re: looking for schematic of a bandpass filter
Subject description: simple to build and with a dual potmeter
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Grumble wrote:
Help!

I'm looking for a bandpass filter where it is possible to shift the center frequency with one dual-potentiometer.
I know there must be some, but I cant fint them...
Power supply: +12volt, -12 volt
Center frequency: 300Hz - 3kHz

This times it is really hard to find a filter which is not voltage-controlled. And most of them are children of generic state-variable filters. Perhaps only guitarists are still using filters with potentiometers. Here is one of them (Anderton super tone control).

Instead of potentiometers people uses OTAs, FETs, DACs... to control filters by voltage or by Arduino Smile
Below are some examples of such filters if you change your mind about way of control [FET VCF from gasboss Smile].
Simplest to build but hardest to modulate are the state variable filters where resistors (potentiometers) were replaced by multiplying DACs.
[from the AD8684 datasheet]
[from the AD7628 datasheet]


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Grumble



Joined: Nov 23, 2015
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PostPosted: Mon Nov 19, 2018 5:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you all for your input!
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kaputtpanzer



Joined: Nov 02, 2009
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PostPosted: Mon Nov 19, 2018 11:20 am    Post subject: Reply with quote  Mark this post and the followings unread

This ist a very easy to build sallen key filter, that usually utilize a dual pot instead of the vactrols...

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Project_2501



Joined: Jan 31, 2018
Posts: 49
Location: Los Angeles

PostPosted: Mon Nov 19, 2018 4:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

MFOS State Variable Filter maybe? 12v -/+ with LP,BP,HP

I have this one on the bench, not completed just yet Twisted Evil

http://www.electro-music.com/forum/topic-53353.html
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