where is a schematic for an LFO that looks like this? :D

[darron]

looks ideal.. taken from this website:

http://www.effectrode.com/delta-trem/delta-trem-in-depth/


would love to play with it in a 9v semi-condutor setup...

[samhay]

Over yonder at the other forum, they have traced the Effectrode Tube-Vibe. The LFO is generated by a PIC microcontroller and I would imagine that the same approach is used for their tremolo.

[darron]

ah bugger. i thought i remembered seeing it as a 170v tube schematic somewhere. i was driving and tired at the time lol.

LINEAR through SINE through SQUARE sounds really awesome. maybe a little too good to be true with a simple-ish analog circuit. but yep a PIC is probably the way to do it perfectly.

[merlinb]

You could get the range shown between 12 o'clock and 5 o'clock on the knob by using a triangle wave generator. Send the triangle to a comparator to generate a square wave with the same phase, then simply blend between the two signals.

[darron]

You could get the range shown between 12 o'clock and 5 o'clock on the knob by using a triangle wave generator. Send the triangle to a comparator to generate a square wave with the same phase, then simply blend between the two signals.

hmmm.... do you think blending between the square and the triangle would leave a nice sine wave? looks like it might do something similar.


what about using the standard dual opamp setup and just blending between the square and linear outputs? might have to get out the scope and breadboard soon....

[merlinb]

hmmm.... do you think blending between the square and the triangle would leave a nice sine wave? looks like it might do something similar.

Uh...no...  To get sine you have to remove harmonics, not add them.

what about using the standard dual opamp setup and just blending between the square and linear outputs? might have to get out the scope and breadboard soon....

The phasing is wrong. You'll get a kind of herringbone waveform- difficult to describe in words! (draw it on paper and you can work it out).

[slacker]

You can do tri to sine to square by hard clipping the triangle. Look at the easy vibe LFO for the basic idea.

[blackieNYC]

The Magnus modulus has the triangle/ square blend pot and it works well.  They are both the same amplitude.  But at no point does a sine wave appear on the scope. I don't really miss it.  If I'm going to knock myself out for an LFO waveform, it will be more exotic than a sine.
http://www.diystompboxes.com/smfforum/index.php?topic=72527.0
(I had no luck with the tremolo jfet extra feature, and borrowed the tremulous lune vactrol. FYI)

[samhay]

ah bugger. i thought i remembered seeing it as a 170v tube schematic somewhere. i was driving and tired at the time lol.

It looks like the audio path is all-tube, but that's it.

The LFO used in the ROG Tri-Vibe is pretty cool, and you could certainly tap off a square wave too.
http://www.runoffgroove.com/tri-vibe.html

Alternatively, take a look at the Tremulus Lune, which has a rather malleable LFO.
Edit - I think this is essentially the same LFO as in the Magnus Modulus.

[Mark Hammer]

There are all sorts of "waveshaper" circuits out there in the DIY synth universe.  Elektor used to regularly publish some back in the golden era.  Most of these circuits, however, are geared towards oscillators in the audio range, the idea being that folding this and that over would produce more interesting distributions of harmonics.

Seems to me no reason why one couldn't simply scale the relevant caps appropriately and adapt such circuits to the sub-audio control range.

[darron]

i had a think last night merlinb, and of course you're completely right on both accounts! shows what i know. would love to have time to play around with synths...




i already have something setup in the dual opamp config like the tremulus lune, switchable square to lin. it's a cool and common setup that you can use to power lots of things. i was looking for something now though more along the sine wave line for something more choppy.


i really like a linear wave for something sweet. some people like sine wave for an old amp-like effect. and then a square wave can be cool for some broken up fuzz tones. that diagram was just too perfectly ideal, but yeah digital might be it.

could use a centre tap pot to blend all three... now it's getting messy haha.




i'll look into the tri-vibe's psudo-sine! thanks.



like Mark Hammer said, I agree, if there was anything out there could change the values to bring it back down to audio range. or sub-audio rather.

[darron]

i'm going to play with a ICL8038

has simultaneous sine/square/lin outputs




anybody have any experience with these? small bear has them $10.   i just ordered 3x from china delivered for $3 lol. try my luck eh