thru zero VCO

gabbagabi · Last edited by gabbagabi on Thu Dec 14, 2017 3:39 am; edited 3 times in total

I drew up and soldered this,
but Iam not shure if this is "thru zero ish" enough, because not all (or no) of the zero crossings are looking so nice roundish like i saw it elsewhere

i really like to haer your opinions

cheers bb
gabbagabi

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vladosh · Posted: Fri May 20, 2016 3:45 am Post subject:

those shapes look interesting for such a small parts count , congrats on the build , could you post some recording from the oscillator , thanks for sharing

gabbagabi · Posted: Fri May 20, 2016 10:02 am Post subject:

i hope u can hear something interresting out of it Smile

in some i applied a static sinus lfo and sweeped with the cv from -15V to +15V

in some i changed the freq of the sinus lfo and applied a adsr triggered by hand

Dist Sin VCO LFO 20HZ Sin.mp3

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dist sin vco sin lfo adsr.mp3

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saw vco variable sin lfo hand adsr.mp3

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SAW VCO sin lfo 111hz plus minus 15V cv sweep.mp3

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SIN VCO sin lfo 111hz plus minus 15V cv sweep.mp3

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vladosh · Posted: Fri May 20, 2016 12:18 pm Post subject:

modulations sound rich , thanks for the sound samples , cheers

soundworker · Posted: Fri Jun 17, 2016 1:20 pm Post subject:

TZ VCO can go to 0 herz, oszillation stops. Only TZ VCO can do.
Modulation TZ produces FM-sounds when modulation is going TZ.
In your soundsamles I can´t hear either.
Its seem you are discharching the integration cap depending of sign of modulation CV, but it is not going through zero. It produces a rich color of waveforms. For real TZ you need a cap in the plus and minus part.

klangbauköln

Electric Druid · Joined: Mar 13, 2012 Posts: 44 Location: UK

Moosgummi · Joined: Feb 01, 2015 Posts: 15 Location: Hiltown, Germany

I don´t really get what´s going on here, but the offset differences are only on the saw wave. I guess it´s a result of the resistor change needed to magically create the saw...
Could a capacitor on the output even this out, or is more magic needed?
Well, I should just build this great simple circuit and try it myself, right?

Edit: Another thing I don´t understand is how the pitch pot works. If I put it to ie 8V, shouldn´t it always stay positive with a +/- 5V input?

soundworker · Posted: Mon Sep 05, 2016 1:01 am Post subject:

Look what I found:

Osamus TZVCO_TZ3b.png

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gabbagabi · Posted: Mon Sep 12, 2016 3:03 am Post subject:

why i got no eMail notification on your posts? Anyway.

I used the Hangover yesterday to going back to this circuit.

First i found a second TZVCO Idea in the folder that ive forgott totally, starting point was the nicolas3141 supersimple saw vco.

Then i played around with offset compensation for the SAW, by using a double switch.

After that i had some fun by simulating the modulation of some points in the circuit.

@soundworker: nice find, and for osamu a, lets say, "easy" design Wink

@moosgummi: you are rigth, i was thinking about that myself to, may the pitch polarity should follow something, but what: the LFO polarity? hm, i guess TCVCOs living of modulations (that are going thru Zero pitchCV ), otherwise they just producing waveform like "normal" vco do. we will see where it goes...

@fyi: the trick with the SAW-Switch is taken from elektor, A. van Ginneken "präziser VCO" (precise VCO), http://sites.prenninger.com/elektronik/elektor/halbleiterheft-inhalt/elektor-1980, it is also in one of there "30x Schaltungen" books

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gabbagabi · Posted: Sun Aug 13, 2017 8:52 am Post subject:

moin!
While listening to the Specials, which is always a sign of a profound hangover, i had the great idea to update some schemos.

attached u find the new version of my TZVCO.
in and output buffers nor waveshapers are included.

enjoy yourself,
its later then u think
cheers
gabbagabi

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L´Andratté · Posted: Sat Aug 19, 2017 9:48 am Post subject:

Very nice in it´s simplicity, this is linear cv I suppose? What is the cv voltage range?

Definitly will give this a try as a replacement for the woolaston saw vco in my battery powered synth-to-go!

gabbagabi · Posted: Wed Aug 23, 2017 5:10 am Post subject:

Thank you for your interrest.

yes it has linear response. The Input voltage range is only limited by the opamp u use. A good one +/-15V otherwise something like +/-12V.

I see tzvcos more as additional vcos, cos the real vco tasks you can serve better with the classical designs.

keep in mind that u need at least an other vco in front of the tzvco to make sense of the thru zero funktion

a minimal setup in my opinion would contain: classic vco, tzvco, 2xadsr, 2xvca

what iam doing so far is:

pitch adsr - vco- [vca-adsr]- tzvco -
[final vca-adsr]
pitch adsr - vco- [vca-adsr]- tzvco -

and iam more than happy with it, since this i never was thinking that i need a filter (anymore? Smile

)

in the next days i will make some sound samples

cheers, gabbagabi

gabbagabi · Posted: Sun Aug 27, 2017 4:21 am Post subject:

ok

first: basic tone, sin-out of common vco feed into tzvco. just to visualize the shape of the wave.

Second: saw-out of common vco with ADSR-Pitch feed into a modulated VCA to tzvco- tcvco tri output. Hand crancked modulation sense pot on tzvco.

Third: Adsr is modulating the pitch of the common vco and the VCA , VCA out to TZVCO In. Then i switched from low(635pfF+2,2nF) to high (635pF). Hand crancked modulation sense pot on tzvco.

Fourth: out of common vco feed into modulated VCA then tzvco, i changed the modulationg waveforms from Sine - tri -saw to rec( i handmodulated the pw a little bit)

For me analog FM is kind of "unstable" even more if u work with more then two oscilators and feedback. So my own rule is if u find a nice sound - press instantly record, u will never find it back.
Second thing is u cant play it "tonaly". Just record that sound and than may pitch it in the DAW.

cheers,
gl,
hf

gabbagabi tzvco basic sinus.mp3

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Patch tri out - saw mod.mp3

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same adsr patch switch from low to high.mp3

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sinusout-mod-by-sin_tri_saw_rec.mp3

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gabbagabi · Posted: Mon Oct 16, 2017 10:35 am Post subject:

new version

edit: startframe of the gif has more information now

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Ricko · Posted: Tue Oct 17, 2017 8:16 am Post subject:

Lovely to see minimal designs! (Not that there is anything wrong with elaborate designs, if it represents good engineering, of course.)

Rick

gabbagabi · Posted: Thu Dec 14, 2017 3:52 am Post subject:

Thx Rick!

Today i add a saw tzvco.

cheers, bb

Saw TZVCO gabbagabi.png

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Ricko · Posted: Thu Dec 14, 2017 7:23 pm Post subject:

Nice trick with the comparators!

(Oops I misread them; I thought you had put inverting halfwave rectification, adding this at twice the signal level, so that the negative saw got reflected about 0V. That would be a nice circuit too.)

gabbagabi · Posted: Sat Dec 16, 2017 6:25 am Post subject:

Hi Rick,
good idea and i will make a note about it, but i guess i will stick to the comparators.

I have putted two comparators because after the first one u could find some "ripples" in the square wave (there where the Saw touches gently the 0V line), after the second they where boosted out.

R11 and R12 in the schemo have probably wrong values, they are more likely 10k or 100k, have to confirm this.

I would call this first version of this circuit "the precise one". I have already simulated a component saving version, which is expected to be less precise.

I have attached a preview of it.

a nice weekend for us all

cheers, bb

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gabbagabi · Posted: Mon Mar 05, 2018 7:57 am Post subject:

of course the idea of inverting the signal after the integrator and before the trigger can be applied to a saw-vco as well

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Grumble · Posted: Wed Mar 07, 2018 1:23 am Post subject:

I really like to follow the process of design of this VCO, but the voltages you mention in this diagram are confusing to say the least..

gabbagabi · Posted: Wed Mar 07, 2018 8:11 am Post subject:

sorry

i thought nobody is listening Smile

the green one is the CV
the red one we could call the RAW-SAW
the blue one is the final result after processing it with a trigger which changes polarity when the voltage of the raw-saw (not the frequency) goes thru zero.
a part of that rectangle signal is then mixed thogether with the RAW-SAW to center it around 0V.

Grumble · Posted: Wed Mar 07, 2018 9:29 am Post subject:

Haha, no I mean the voltages you place at the opamps, like vcc, vdd, 15v and -15v.
Some just seem to float and not connected to anything Wink

gabbagabi · Posted: Wed Mar 07, 2018 10:20 am Post subject:

got it,
thx for the head up.

will be better in comming schemos.

cu

elcoco · Joined: Feb 12, 2016 Posts: 8 Location: London

Wow these look great, I'll have to give them a try to hear tem in person. Any idea if running this off 12v would work as well as 15?

gabbagabi · Posted: Wed Mar 14, 2018 12:18 pm Post subject:

u need a dual supply
they are designed for +/-15V
it will run from +/-12V
only the amplitude wil not be 5Vpp
a bit less

please let us know how it turned out

at the moment i have no energy in the workshop
so i cant go for further testing these days

the triangle versions are all fully tested
only the first saw version i had on breadboard, like u can see there is a "real-life-scopie"

cheeres, bb
gabbagabi