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 Forum index » DIY Hardware and Software » Lunettas - circuits inspired by Stanley Lunetta
Simple LFO schematic, opinions?
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JingleJoe



Joined: Nov 10, 2011
Posts: 878
Location: Lancashire, England
Audio files: 14

PostPosted: Fri Dec 07, 2012 2:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't know about RF (radio frequency) noise but there's allways the problem of induction- any two wires or pcb track running near one another can induce a current in one another so if you have any high currents flowing through wires, the larger current will create a greater electromagnetic field around the wire thus inducing a signal in nearby wires.
Reduce the current flowing to solve this.
Also that 100 ohm resistor sounds like a bad idea to me, I've never seen that done before, maybe a 10 ohm resistor to prevent direct shorts but 100 ohm in line with the chip? That'll just power starve the IC.

Try putting a nice big cap, something like 470u or 1000u accross the power supply Smile I have done that in the past to remove interference caused by 555 timers and other oscillators in high gain amplifiers (gain>1000) which were all on the same power supply.

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Rolbista



Joined: Nov 17, 2012
Posts: 23
Location: Poland

PostPosted: Fri Dec 07, 2012 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, i'll try that, one more thing, I'm currently using a switching transistor with an LED for a rate indicator, but could i just put an LED in parallel with whatever i'm modulating with the LFO? stick it on the output?

*EDIT* would it be a good idea to ground all the unused pins?
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hedefalk



Joined: Aug 29, 2017
Posts: 51
Location: Stockholm, Sweden

PostPosted: Tue Sep 12, 2017 7:54 am    Post subject: Reply with quote  Mark this post and the followings unread

I just built this on a breadboard with a 074 and was going to move it over to something more permanent. I noticed that I have

Sine Vpp: 11.8
Square Vpp: 22
Triangle Vpp: 7

1) Do you think there's anything wrong in my build with those numbers?

2) If not, I'm thinking I could probably use my last opamp from the quad packageā€¦ What's your recommendation as far as usability goes? My intuition would be to maybe double up the triangle since this is the lowest Vpp now? But maybe it's more important to have a strong sine? I'm super noob at actually trying to y doing anything with the synth so haven't got a clue on what is important yet Smile
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hedefalk



Joined: Aug 29, 2017
Posts: 51
Location: Stockholm, Sweden

PostPosted: Tue Sep 12, 2017 7:57 am    Post subject: Reply with quote  Mark this post and the followings unread

One more thing, the schematic has a 100nF timing cap. I'm thinking I'll use a STDP switch with two caps for range selection for kicks. I'm thinking 104 and 103, is that reasonable? Tried the 103 and got a little bit higher in the audio range which might be useful. Or should I rather extend range in low end with a electrolyte?
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