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Three-phase LFO

Three-phase LFO

Prottype build on the universal board
This module put the 3 signal that 120 digree shifted each other at a time. It's based on Aphase LFO designed by Rene Schmitz. We can modulate 3 VCO by this. We may get so fat sounds I expected.
He said that this is self oscillated low pass filter and use swithed capacitor instead of resister to change the rate of LFO. We need VCO as clock generator for swithed capacitor of main generator . and 3 buffer for outputs.
Rene use C-MOS Logic IC 4093 for VCO but, I use 4069 that the rest gate of main generator to omit 4093. I use the core of 4069VCO that also Rene's design.
this method to use 4069 get so many currents and it may get heat. I try this in actuly but there is no trouble .
If you put the output of 4069 to audio and change R5 to pot and tune it, then it may work as VCO, I think.
I got mistake when I build it on the bread board, I misunderstand 220n as 220p. It works in audio area but I down its frequency to LFO area then it can't work. I can't find the point where I mistaken.
There are small parts, in these days, but 0.2uF is still big. I prepare my PCB pattern to be able to use not only small but also big size one.
I add the simple VCA to the buffer. It's based on LFO Delay written by Masahiro Kunii. And I put more idea comming from the methods around Q20,Q21 of schematic diagram of Roland's DR110 at E^Music DIY Archive.

As my usual, the member of Japanese local BBS at abe's page gave me so big advice. ( thank you! )

circuit simulator

I started to learn about "circuit simulator" This will allow us to see the result what I want to know before I build them. I use this for easy VCA to build.


We can get free circuit simulator from here. there is only Windows version. I use it on PC emulator on Machintosh. In these days,there is so many software that I want to use in windows, so I got cheap one. But it still can use on emulator on Machintosh.

orignal version
this is the result of the simulation of Kunii's single transistor methods. He designed it for delay vibrato only and it don't need big range (there is no need +/- 10V or so). He designed it as the accent for one box synth or something. and he throw away the linearity. In this point of view this methods is simple enough and work well.

schematic diagrams in gif format ishere. CKT file is here.

double pnp version
this is the result of 2 transistor version based on the advice from Tanaka. The point of this methods it is the level of input to the emittor. It work well for the signal center 0V and +/-400mV. If it's over it, then it get distortion.
there is almost no distortion to use as the delay vibrato.
schematic diagrams in gif format ishere. CKT file is here. Beware the conversion of line end code by web transfer

Both circuit modulated by this signal

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"three Phase LFO " Copyright 2003, Motohiko Takeda, Crow Hill Laboratory
Motohiko Takeda Mail:takeda@aleph.co.jp