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VCLFO ic or easy circuit?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author VCLFO ic or easy circuit?
for a new project I need around 40 VCLFO's.
With TRI of SINE outputs.
Is there a small and simple circuit around?
Or an that has this IC?
What about this?

Each of those little boards has two VCOs, using a 13700, 074, and 072. Triangle outputs. I can send you the PCB details if you like.
Paul Perry
Agree, the simplest "VCO sin plus triangle"is a LM13700 triangle oscillator as per data sheet for the triangle, followed by an overdriven LM13700 section for the sine.
Do you need them to be analog? I'm not so computer/digital savvy but I imagine that it might be easier and more cost effective to whip up a design using something like a Teensy/Arduino/Pi with some I/Os?

There is also the Electric Druid VCLFO - in some ways its overkill for what you want (maybe you would find the extra features helpful?), but depending on your total design and implementation maybe it makes sense. Def not as cheap as bulk op-amps, but maybe you could get a price break at 40 pieces if you ask nicely?
Thanks guys!
Nigel, it would be great to have the PCB!
There are two very simple circuits for this. First, you use an LM13700 looped into a shmitt trigger. You can use the buffer on the LM13700 since the amplitude switch point is controlled by the trigger, not the LM13700. This uses a single opamp and 1/2 LM13700, so with a dual opamp and a LM13700 you get 2x LFOs. The second circuit uses three opamps. One opamp is wired with an FET to invert depending on the FET input. The fet input is fed from a shmitt trigger, which is fed from an integrator, which is fed from the conditionally inverting opamp. If you don't have a V-to-I converter in mind, this is simpler.

Also, 40 is a lot. You have piqued my curiosity. What are you planning?
Moog source LFO is nice and gets you an added vca as well for the other half of lm13700 or just two VCLFOs.

so a lm13700 and tl074 with 6 transistors gets you x2 as previously pointed out. [/img]
I'm building a kind of loudspeaker orchestra and want to control all the speakers separately in multiple ways.
It is probably easier now than it was in 1958 grin

Philips Pavilion 1958
If the LFOs have to be analogue and you need that many, how about very simple CMOS inverter oscillators + filtering?

digital, but i don't think analogue was demanded, and that's voltage controllable + has sine and triangle outputs.

buying 40 of them will be somewhat expensive but probably not more expensive than building 40x of any of the designs mentioned so far.

you could probably run 40 separate tri/sin lfos easily with one of the newer teensys for example, but you'd still need enough ad/da to interface them and probably some protection and level shifting...
Here are the PCB and component overlay diagrams for my dual VCO board. It's basically the same as the nonlinear circuits Dual OTA VCO circuit, but stripped back to suit my requirements (triangle output, three expo VC inputs, suitable for home PCB etching, and compact). I've made two drone modules with them (one with two modules / four oscs, one with three modules / six oscs) and they track reasonably well over at least a few octaves. For an LFO, you'll need to increase the timing capacitor - I'm not sure what effects that will have.

Some notes: the board has five wire links on the component side, one running underneath the 072. The 1k resistor between the two transistors is a tempco, using a regular resistor may or may not make a difference. The 68k resistors which set the minimum frequency were a little low for audio, and I changed them to 150k in my builds. The blank square pads are for 100nF SMT caps across the power rails. The inputs and outputs are all on one side of the board - I put connectors on that side to mount multiple boards onto a backplane.
The MFOS VCLFO meets most if not all of your requirements.
I'm not sure of you would find it small/cheap enough but it does have triangle and sine outputs and VC control.
The PCB artwork is on the website if you want to try and make your own maybe a bit cheaper. Two sided but the bottom has very little on it and you could probably just use links.
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