electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
<on air> Faux Pas Quartet and friends Music From Last Thursday
Please visit the chat
 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
My little 'Lame' Filter
Post new topic   Reply to topic Moderators: mosc
Page 1 of 1 [4 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
acidblue



Joined: Jun 26, 2009
Posts: 192
Location: The Darkside

PostPosted: Thu May 08, 2014 9:48 pm    Post subject: My little 'Lame' Filter Reply with quote  Mark this post and the followings unread

I call this the Lame Filter, as it is so simple it's Lame.
Basically a passive low pass filter fed into a non-invertting amp.
After bread boarding I discovered it does not behave like it should.
If I replace R2 with a 100k pot, so I can adjust the gain, it hasn't any effect.
Turning the pot doesn't really change the gain, the gain seems fixed.

Adjusting R1 seems to be have more effect on gain than R2, or maybe its tone, definitely not frequency.

Using a 741 with a single supply with virtual ground.
Posting this so maybe someone could improve on it and maybe get some use
out of it.
Actaully sounds ok being fed a couple of 40106 osc's.
Tried adding resonance by feeding single back into itself, from '+' pin to the output pin with a 1uF cap and 100K pot in series pot but that didnt work.

Back to top
View user's profile Send private message AIM Address
acidblue



Joined: Jun 26, 2009
Posts: 192
Location: The Darkside

PostPosted: Fri May 09, 2014 3:52 pm    Post subject:   Reply with quote  Mark this post and the followings unread

Been experimenting with the Lame Filter and came up with a better design.
A.K.A. Not Sure Why This Works Filter
I thru out the 741 with VR ground, still dont have a dual power supply next pay check I'll get one I promise Wink .

Used a Lm358 instead since they're designed for single supply and after of
just trying different things I came up with the following schematic, tested on bread board and IT WORKS!
Not the greatest filter but sounds ok for Lunetta use IMO Smile
Throw one together and try it out, also try different cap values, like 100nF and above.

My theory why this works:
The First pot and cap combo is suppose to be the low pass filter, although i suspect it's doing other things, as it seems to speed up the 40106 Osc's I been feeding it and if it you turn it low too much it sputters dies, kinda like a voltage sag.
The second pot is the gain from the 358, the 100k resistor to ground is the key, your mileage may vary.

Feeding the filter with 3 oscillators from a 40106 chip:



Back to top
View user's profile Send private message AIM Address
gdavis



Joined: Feb 27, 2013
Posts: 161
Location: San Diego

PostPosted: Sat May 10, 2014 12:47 am    Post subject: Reply with quote  Mark this post and the followings unread

acidblue wrote:

The First pot and cap combo is suppose to be the low pass filter, although i suspect it's doing other things, as it seems to speed up the 40106 Osc's I been feeding it and if it you turn it low too much it sputters dies, kinda like a voltage sag.

Because when you turn it down it shorts whatever is connected to it to ground. Not a good thing to do.

_________________
My synth build blog: http://gndsynth.blogspot.com/
Back to top
View user's profile Send private message
acidblue



Joined: Jun 26, 2009
Posts: 192
Location: The Darkside

PostPosted: Sat May 10, 2014 11:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Doh!
I knew it was something.
I updated the schematic, added a 1k resistor to the first pot to ground.
This doesn't solve the problem completely, just keeps the filter from
dieing completely when turned down.

Still a work in progress.
Back to top
View user's profile Send private message AIM Address
Display posts from previous:   
Post new topic   Reply to topic Moderators: mosc
Page 1 of 1 [4 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use