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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
How to apply an LFO?
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CHRISKELLY



Joined: Apr 08, 2018
Posts: 36
Location: England

PostPosted: Sat Apr 14, 2018 4:34 am    Post subject: How to apply an LFO? Reply with quote  Mark this post and the followings unread

I’m looking to add an LFO to my circuit, to create a rise and fall in the volume of a drone.

I’ve found a few nice ideas but what i’m not sure of is how to use it the change the volume.

Is it as crude as instead of connecting the power pin to a chip straight to Vcc, connecting it to the LFO, so that the voltage input is fed and starved? Or should the LFO alter the volume control at the mixer for the chip?

If it is the second option, then do you need to use a transistor somehow to effectively alter the resistance at the mixer?

Bit confused about this Confused
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g.gabba



Joined: Nov 29, 2008
Posts: 367
Location: berlin
Audio files: 23

PostPosted: Sat Apr 14, 2018 6:20 am    Post subject: Reply with quote  Mark this post and the followings unread

hi,

for changing the volume of a signal by using an LFO one use normally a vca.

one of the simplest (opamp-free) VCAs i know is the DR-110 VCA.

As far as i know u lunetta guys dealing mostly with rectangle signals - so may u could simplyfy this vca even more,
i did a simulation of what i mean,
the resistor values are only examples, play around with them, the output is not buffered.

an other very simple but not opamp-free vca for rectangles u can find here (this will also work with +/-9V):
http://electro-music.com/forum/topic-65679.html

after seeing my old idea, came the next (second pic) how to make it simpler and single supply.

in addition your idea about feeding/ starving the Supply pin - but u have to do this by using the signal. the simulation did not have really worked here. the diode is meant as protection against negative voltages.

chers, gabbagabi

edit: bought an "e" for cheers, another 3€ down the drain


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Last edited by g.gabba on Sat Apr 14, 2018 8:03 am; edited 1 time in total
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CHRISKELLY



Joined: Apr 08, 2018
Posts: 36
Location: England

PostPosted: Sat Apr 14, 2018 7:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the advice gabbagabi Very Happy
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g.gabba



Joined: Nov 29, 2008
Posts: 367
Location: berlin
Audio files: 23

PostPosted: Sat Apr 14, 2018 8:00 am    Post subject: Reply with quote  Mark this post and the followings unread

pleasure,
keep in mind that only the circuit behind the link is tested,
although i would bet the first in the second pic will also work.
I used lm324 quad-opamp in the simulation, cos i dont know the single äquivalent.

cu
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