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DIY Thru Zero VCO *build a TZVCO FrontPanel Standardized
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3  Next [all]
Author DIY Thru Zero VCO *build a TZVCO FrontPanel Standardized
2018-06-02 FrontPanel Standardisation
2018-05-20 Building EN129 updated
2018-05-10 Updated layout 3Ux10hp + From me to you
2018-05-10 Updated layout 3Ux10hp
2018-05-06 Initial FP design
2018-05-06 Will be 3U by 8-10 hp module
2018-05-03 Video Demo 3 12 minute Soundscapes
2018-05-02 Video Demo 2
2018-05-01 Video with Audio sample 1
2018-05-01 Start of thread

Hello all,

As the DIY Programmable Moduar (as discussed in storder=asc&start=25) is going to take quite some time before its existance, I will be working on other projects in between anyhow.

I had a look into the ElectroNotes mentioned by ashleym, and did a quick breadboard build based on the ElectroNotes129 but with quite some modifs as to fit modern electronics.

Anyone who is interested in this, pls let me know.
Pls also inform me with the options you would be looking for.
It would be an additional TZ VCO to the ones on the market, but one might be interested in it.

Here's already a picture of the setup,
I'll post a video with audio later today.

dot matrix madness
Interested in the schematics and maybe a PCB for TH compounds.
Here's a first audio sample.

The square wave is the rectified sine modulation.
It can be used to indicate the thru zero transistions.
Both TZ-VCO and modulation signal are Sine signals.
The Modulator is created by a standard VCO.
Both the standard VCO and the TZ-VCO are connected to the same note on the keyboard but they are detuned in octaves and semi-notes.
This sample only uses a ADSR and no filtering.

All feedback welcome.
B rgds,

I can't figure out how you find the time to knock out so much stuff so quickly, Boogie. It's impressive.
Revok wrote:
I can't figure out how you find the time to knock out so much stuff so quickly, Boogie. It's impressive.

Seconded. Excellent breadboarding skills, quite apart from circuit design.

One thing that would be good on a TZVCO like this one is a VCA on the linear FM input so that you can vary the depth of modulation. I know that some of the electronotes designs had this but not sure if this one does.

It's great to see / hear the EN129 design in action. The earlier electronotes design (EN75 I think) has been reincarnated by AndrewF as the NLC Plague of Demons. Very cool to be able to play with both. I'd be interested in a PCB for this one for sure.
That's sounding very nice! I've always wanted to build something similar to the EN TZ.
Wow I'm interested in this! we're not worthy
Rex Coil 7
Is there any way you can do another video with it playing longer notes, other than very short percussive hits?

Perhaps holding a note while certain things (???) are changed in real time as you hold the note?

That way sonic changes may be heard as they happen when you sweep certain controls.

And we could see super cool wavey stuffs on the scope too!

Hello dot matrix madness,
Interested in the schematics and maybe a PCB for TH compounds.

Some basics about a TZ VCO can be found here:
The author already explains very nice how the thing works.

Someone already put it in a better readable format in schematic capture software, and already implemented an improvement and provides his schematic here: vco_720.pdf
In this last file, one can find a PCB layout, schematics and some scope plots.

I started my design from the same source, and only found this document early today. My design has some differences compared to the one in the electro-music 720.pdf

Nevertheless, I think the 720 file should be useable as well.
All credits for the 720 to the rightfull owner.
@ Rex Coil 7
below is another one, but also percussion, though longer decay. (I did both of them yesterday)
Starts with a (I think nice) low bell sound.
There are several moments throughout the video (+9 minutes) where I modify some settings during decay.
Decay is long enough to hear one note transition into the other.
It should aleady provide a nice idea. Most modifs happen after time stamp 5.00 min.
I'll put a couple minutes of continuous tweeking online by the weekend.

@ cygmu
will keep that in mind and might add it to the modulation signal in the video I will record next friday or in the weekend.

@ Revok
sometimes a Coffee Addiction FTW , sometimes a Guinness ftw! and last but not least, an understanding partner hyper

As per request,

a 12 minute Single Thru Zero VCO soundscape.
No filtering.
Contains very low frequencies and from time to time some pretty high as well.
Use good speakers or headset.
The PCB on the right bottom is a standard VCO of which the Sine is used to modulate the TZ VCO


Rex Coil 7
thumbs up thumbs up thumbs up

Rex Coil 7

thanks for the thumbs up,

but what do you mean with Boogie Down ?
Doesn't realy sound positive ?
As I'm not an American,
I may missinterpret the pictures.
Can you pls clarify ?

Rex Coil 7
HAA!!! (PM'd you with deep explanation)..... also .... can't resist ....

The song The Pope is quoting .....

Another song with a "boogie" reference ....

IT'S ALL GOOD MAN!!!!!!!!!!!!!!!!!!!

thumbs up thumbs up
Hello Rex Coil 7

I just read your PM,
thank you for clarifying as well as for the above post.

All the best,
This VCO sounds really lovely — I’m keeping an eye on this thread!
Amazing that you have already designed this!!

Have just had a listen to the two demo's and the soundscape and am super impressed!

I second all the positive comments above.

Boogie you rock Rockin' Banana! nanners SlayerBadger!

I am certainly interested in this project but am not sure if you mean it is part of the programmable system or will be a separate module?!

am not sure if you mean it is part of the programmable system or will be a separate module?

Some years ago I started with the idea of a programmable modular, which is the system so far based on kind of mother boards with plug-on's.

Today I have as plug-on modules (I call them hybrides)

* Transistor ladder filter
* State Variable Filter (2180 based)

For this one, the TZ VCO, I was thinking on doing it as a separate 3U by 8 or 10hp module.

I can always do a derivative to a hybride to be plugged in the programmable modular.

So for this thread the TZ VCO is going to be a 3U by 8 or 10hp module.
As you may have seen in my previous posts/threads, this one is also going to be a SMD populated PCB with through hole components.
Below a first render of the module.

Nothing is defined as final.
All feedback and suggestions for additional functionality etc. is welcome.

Rex Coil 7
Boogie wrote:
.....All feedback and suggestions for additional functionality etc. is welcome.

I.) Include "sync" input, for hard sync alone at least, hard and soft at most. If soft sync is included (along with hard sync) add a soft sync input signal "level" control to be able to attenuate the input signal while using the soft sync feature. Listen to soft sync demos/videos for examples of how powerful this can be.

II.) Use knobs like something that may be easily seen in low light conditions (dimly lit studios, dramatic stage lighting, and so on). Something that will provide a visual contrast against the panel so the ~line~ on the knob is easily seen.

III.) Consider using jacks that have nuts which will attach the jack to the panel (such as Doepfer). This is something that some people see as a durability issue.

IV.) Consider placing all jacks along the bottom of the panel .... this creates a lot of room around the controls for fingers to operate them. Look at AJH Synth as an example.

Just some suggestions .... all said and done it is YOUR design so please do what you feel is best.

thumbs up
Sounds Awesome! Looking forward to seeing this progress!
Sounds great, would be interested in a board + panel when it's ready.

Would prefer the option for unpopulated smd as well if pos.

Edit: as for feedback on the design, a built in index vca is really handy, especially on vco's designed specifically for their fm capability! As Rex said though, go with what works for your plans.
Sounds awesome. Is it the same circuit as in the paper or did you make modifications? Could you post a schematic? Thanks!

it's based on the schematics of

There's a bias problem in the orginal which I've removed.
The sine generation has been replaced with a (also modified) two transistor approach (THD < 0.2% now)
As people have been asking for the VCA in the FM path, I still have to implement that.

Honestly, I'm not so much into publishing schematics.

For anyone willing to do something like this, pls make a start with breadboarding and PM me where you're blocked or need assistance, I'll gladly help you step by step to achieve some results, and on top of that, it would be really DIY.

One would be amazed how much it takes to do good breadboarding (analog circuits wrt hum, noise and stability).
For a start, I would advice to take some breadboards that are glued to a metal plate (just a very thin layer of glue). Then connect the GND (0V) a couple times to this metal plate, one will be amazed again how much improvement this gives wrt hum and overall stability.

Always willing to help if time allows.

That's OK.

I am trying to do a stripboard layout of the original design (using KiCad and VeeCAD).

I was just wondering if there is anything to look out for that does not work well in the original circuit.

You mentioned a bias problem. Where is it exactly and how did you fix it?


One more question: are you actually using LM3080/CA3080 OTAs? The electro-music file mentioned above that a replacement with 13700s would not work?
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