Hi all.
Not sure if I’m using the correct terminology.
I’ve built a simple LFO from this strip board layout and it works great.
But obviously on the square out it turns on and off immediately. Also the triangle output doesn’t have much of an effect.
How would I redesign it to fade in and out?
Is it possible from this circuit or would I need to build a different one.
I’ve had a search around and not had any luck.
It sounds like you’re talking about needing a sine or a triangle wave? Not sure what you mean the triangle “doesn’t have much of an effect” since that’s what that does.
thanks for the reply.
Ill check my circuit.
When the triangle out is plugged into the CV input of the LMNC filter I dont hear much of an effect.
When I send the square wave out its easily discernible.
Ill try post a video later.
Thanks.
Commonly with this kind of circuit (without a schematic I can’t be sure) the square wave amplitude is about ±10.5 V and the triangle might be only say ±5 V, so its effect would be smaller.
If it’s not enough amplitude to move the cutoff frequency above and below the VCO frequency, and the square wave amplitude is big enough to do so, it might make for a big difference in the apparent effect. You can try manually raising and lowering the filter cutoff, or the VCO frequency, and maybe find a sweeter spot where the triangle wave produces a more audible response.
Since it’s an LFO you can verify the triangle wave is there, and check its amplitude, with just a multimeter if you set the frequency low enough (~1 Hz or slower), you’ll see the voltage rising and falling.
Thank you.
I’ve just realised I had not grounded the outputs.
I’ll do that and recheck.
I have an oscilloscope coming today so shall post some images of the output wave forms.
This looks like an awfully simple circuit for a Roland LFO. Did they really use this circuit I wonder?
No. That circuit bears no resemblance whatsoever to the Roland 100M. That layout with that false name has been making the rounds, someone probably thought it’d go more viral if they claimed it was something it isn’t.
Thanks. I didn’t think so too.
I’d be interested to see the real one and compare.
You can add a simple pot to the output to fade in and out the LFO as you want, it’s basically a depth control, 100k Lin pot across the output of your LFO with the center and ground maybe through a 1k resistor being the output. Allows you to control the depth. I suspect your square wave is 0-10v and the triangle is +/-5v hence why your seeing ( or hearing) such a difference.
Ok that sounds like a good idea.
How could I do that automatically.
Say set a depth for it to fade in and out at a set rate. Slowly ramping up and down.
Would the triangle be be doing this anyway if the rate was slow enough?
Thanks again.
Well unless you want it doing that continuously you need to trigger the attack and release. So for example if you use a VCA and an envelope AR generator you could trigger an attack/release phase that opened up the VCA and let the LFO out over that cycle.
If you can’t trigger it then it’s not possible. So the next option is to use a second LFO to modulate a VCA and that would allow the first LFO signal through in an undulating fashion.
Ahh. I see.
Sorry for the odd questions.
This really helps.
Thank you.
No worries, anything that requires an envelope, delay etc from the LFO point of view usually requires a trigger to start the cycle.
For example I just built an ensemble unit and added an envelope for attack and release of the ensemble, then I realised when I’d built it that I would have to trigger it somehow, so it was a waste of time. I’m removing the envelope and VCAs.
It sounds like what you’re asking about is having the VCF cutoff ramp slowly up and down, and that’s exactly what a triangle wave LFO into the VCF cutoff CV input will do.
(Unless you’re asking about having the LFO triangle wave amplitude slowly increase and decrease, that would require putting the LFO through a VCA, and then using a second LFO to modulate the first’s amplitude, but I don’t think you are.)
If so then what you have should work, you just need to find the right knob settings so the VCO cutoff frequency sweeps through a range sufficiently close to the VCO frequency. If the LFO amplitude is ±5 V then that’s 10 octaves so that should be plenty of amplitude as long as the VCF cutoff frequency is centered in a good place. If it’s too high then it might not give you much of an effect. Turn it lower in that case.
Amazing what grounding can do.
Like make things work!
On the triangle output I get a nice steady slow rise and fall of +/-4.5v.
All working as it should.
Many thanks for the replies.
Yes it does help the situation, glad you sorted it, I left a ground off a build yesterday, all was quiet until I realized it.
Glad it’s working - If you slow the speed right down does the amplitude decrease? I think that’s an issue with that design from memory… The simple LFO by David Haillant is better and as straightforward, though I don’t think there’s a stripboard layout about.
I’ll check the amplitude.
Ok so I built the YMNK arpeggiator and it’s working fine.
But when I send a signal into the clock input of the arpeggiator from the LFO mentioned above the output is very weak and quiet.
When I send an output from a Behringer neutrons LFO output into the arpeggiator clock the signal is strong and loud.
Any thoughts as to why this may be.
What should I check for?
Many thanks.
What do you mean by “weak and quiet” or “strong and loud”? The arpeggiator only puts out a control voltage to control the pitch of an oscillator. It has nothing to do with the loudness of the sound which would be governed typically by a VCA.
Are you talking about the click signal becoming weaker, maybe you need to buffer the output.
