Dual-LFO Speed mod ?

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josaka
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Dual-LFO Speed mod ?

Post by josaka » Wed Jun 14, 2017 5:11 pm

I have two Dual-LFO ! fantastic already ! ...built by Paul.

however, I would like to have them modulate both faster and slower ! ..
is there any simple mod that does this..?

A hi-low switch?


thanks :)

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Synthbuilder
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Re: Dual-LFO Speed mod ?

Post by Synthbuilder » Thu Jun 15, 2017 2:42 am

It should already have the slow/fast switch. The older Triple-LFO didn't though.

You can change the timing capacitors on the board to alter frequency, but there are a few things to bear in mind. Firstly, the sync function has to discharge the timing cap(s) to work properly. The bigger you make the timing cap the less chance that this will work as it should. You may be able to squeeze a little more slowness from it... but I've not tried it. C1 (LFO1) and C2 (LFO2) control the timing in the slow setting. Increasing them to 1uF will double the time period, ie. half the frequency. But like I say it may cause the sync function to not work correctly.

Secondly, decreasing the timing cap will increase the frequency. There is a limitation on the upper frequency thanks to the way the shape function is implemented. C5 and C6 control the frequency for the fast range in LFO1 and LFO2 respectively. Decreasing the value will speed the LFO up.

Thirdly, changing the timing caps affects the whole range over which the rate control works. For example increasing the capacitor size will slow both the fastest and slowest settings of the rate control. Because of this, changing both the slow and fast timing capacitors may mean that you don't have any overlapping between the slow/fast settings.

Tony

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josaka
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Post by josaka » Thu Jun 15, 2017 3:47 pm

ah yes.. of course .. didn't take a few of those things into account ..
(was a bit tired when posting and managed to forget about the speed switch!!
note to self ..must not post when half asleep)

thanks for the detailed reply tony much appreciated .. ! :)

..may try a slight change to C5/C6 see what happens :)

...can still oscillate the oscillator I guess .. :)


thanks

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