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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
CMOS VCF!
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Psyingo



Joined: Jun 11, 2009
Posts: 248
Location: Canada

PostPosted: Fri Nov 30, 2012 9:15 am    Post subject: Reply with quote  Mark this post and the followings unread

JingleJoe wrote:
I'll post my solution to the resonance problem because psyingo apologized via pm;
You can fix the resonance issue by lowering the signal amplitude, it has probably hit one of the power supply rails you see? Also by changing the offset voltage of the wave, however I am not certain how you'll do that with a 4069, can you simply adjust the input wave biasing?
Sometimes un-evenness in the filtered signal is due to the diode effect causing only one half of the wave to be filtered, there could be internal diodes in the 4069 causing this or it's own transistors can cause it (trannys being a lot like diodes in themselves).


Right, this is why I included the level control on the input, so you could adjust the signal to a decent clean level or push it into overdrive. It makes it more versatile that way, as different uses might not all share the same signal level.

It's good to address that issue though, for people who are thinking about omitting the input level control. if you omit the input level control you will have to lower the signal into the filter, with a fixed voltage divider, or maybe just a larger resistor than the 100k.
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mosc
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Joined: Jan 31, 2003
Posts: 18197
Location: Durham, NC
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PostPosted: Fri Nov 30, 2012 11:30 am    Post subject: Reply with quote  Mark this post and the followings unread

I think that simple circuits like this are splendid. Even though they are not perfect audio devices, they can make interesting and useful sounds. In many cases, they sound better than "ideal" filters, at least to certain ears.

Everyone here is a valued member and contributor. Let's try to phrase things in ways that aren't likely to get others upset. Certainly, name calling and ridicule are not appreciated here. After all, we are a small group of devotees, we need to go out of our way to make everyone feel welcome and included at electro-music.com. Always take the high road.

Let us pray Ohm... respect

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Hollywood



Joined: May 22, 2012
Posts: 17
Location: Ireland

PostPosted: Tue Dec 04, 2012 6:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

@JL, did the 4069ube make much difference? I happen to have one lying around as well as a upb.... suppose I should just get breadboarding and find out!
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