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More Modification to VCO I|
I got temperature coefficient resistor (TCR). I planned modifying VCO I using TCR.
In VCOI, I used CA3086 as component for anti log converter. It has 5 NPN transistors in it, and 2 of them are combine with emitter internally. I use this as dual transistor and the others consist as thermal loop.
One transistor feed back temperature drifting to
the other that be used as heater .And it change the temperature of whole chip.
I use it so that a drift may not be carried out.
I build VCOII with 2SC5168 that I found in "akihabara".
Home page of this transistors maker said that they still make this. But it's not easy to get in Japan.So somewhere some shop I don't know sales this chip.
The maker that had been making 2SC1583 or 2SC3381 said they stoped to make them.
Some oversea resaller still have some of them. But it should be going to be hard to get.
Adding Octave SW
For performing music we should tune VCO. First, you turn course knob to define with about tune. Then you use fine knob to fit your tune to other VCO or musical instruments. This way creates so wide range tune easily. But I think that it not easy to perform music.
If you use VCO for only sounds then it's enough. But when you want to use it for musical instruments, you want to switch tune per octave. and it makes to be enough for one knob to fit tune.
But in this way, if you want 5 octave changing you need so many numbers of registers here. It's same as other part of this VCO. I think that this way is ok for 3 octave. If I want more changing, I should better to select another way. So in this case I made normal ladder and put it in voltage follower and put it to summing stage as same as other modulation sources.
I use Japanese transistors. It has different pin structures from over sea one.I use 3 dual opeamps to make it easy to build.
To tune octave switch, Set rotary switch to most high position and set your DVM to U2's 6pin and turn trim to 4.00V. Next, You can use this switch to scale tune.