This is wave form convert. It can convert saw wave from saw to triangle and anti saw by CV in seamless.
It's same as AKS and VCS3. they are analog synth that are still made and saled. "EMS".(it's home page is here) is its maker.
They are controled by control voltage but there is no connectors. You can find the
way to mod it at here.
And you also found the schematic diagrams in the same page.
And Don Tillman intorduce another method for this in his article on his of page.he call it "Voltage Controlled Duty Cycle Sawtooth Circuit".
He said that it's only a plan and he didn't try to build them yet.
Ian Fritz try another method for this. its page is here.
But I can't understand about this method at all. I will try to learn this later.
And there also is another method to do this. Sam houshu intorduce his method at
local bbs (it's almost written in Japanese).
I try to comfirm his method by software (you need Mcromedia Flash player Ver.6).
And he write 2 type waveshaper schematics diagram based on this method.
It looks easy to build but it can not control by CV.
this schamatic diagram based on OTA. It become to be able to control it by CV. But Still I have some problem in this method.
there is so many trim pots. And It looks so hard to tune them correctly. it still is not for
everyones method. I think I should make their trim pot more less.
I learn about his method and he gave advice to me to use RC4200 for divider / multiplier instead of OTA. And he sent me some RC4200 too. It will reduce the number of trim pots.
Houshu check my schematic diagram and correct my silly mistake. So I build it by
bread boards.this is the result of the wave form.
Overview about wave form
the capacitor c1 that indend to remove gritch value is 470p
c1 = 1n
This is wave morph video in mpg format.
CV moves 0v -> 10V(It's same as ref voltage) -> 0V. It also includes sounds,
but it's so cheap recordings so you should better think that it's
just a sample.
You can also see the input wave form as fixed Saw wave.
there is not only big gritch but also ringing. Houshu think that We should inclease
the value of R15 to decrease the value of C1. but R15 should less than R14, and R12.
so houshu change the circuit like this.
there is almost no ringing but there still are gritchs. And there is Instability for the wave form at the low CV. hrizonal line is CV lowest position is 0V and hiest is 10V.
This schematic diagrams has only one trim pots.It control the final out put levels. it's easy to tune. but we need to use resistors that has no relative error
in several pairs.
I think that I need more stabilty when low CV are feeded. So hoshu add some more functions to my schematics.
- R16 and R17
- to make 1/2 ref voltage. It will produce the K and (1-k), saw and (1-saw) correctoly.
- R1 and R5, R3 and R9
- both pair also make K and (1-k), saw and (1-saw) correctoly.
- R7 and R10 , R11 and R13, R12 and R14, R30 and R31
- each of them will relation to the wave form.
I made small demonstration for this schematics
I connect converter to VCA directory and I put CV to the VCO and
put gate to the EG. EG give CV to this circuit and VCA.
There is no VCF but we can get intersting sound.
- summing amps for CV inputs.
- CV limiter to not to make this cricuit to over level
- More stabilty for ref voltage.
- Voltage shift for ramp output.