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2VL1 Dual 40106 VCO + LFO 12HP Euro DIY
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Author 2VL1 Dual 40106 VCO + LFO 12HP Euro DIY
devinw1
You can always use another VCO right!? Why not 2 of them and an LFO in 1 12HP module?

I got the idea for this after designing and breadboarding a VCO with the venerable CD40106 and it ended up working quite nice, so I figured I'd try and use all 6 units on the 40106 in one module. I ended up using 5, so a good try I reckon!

Features:
-2 Independent VCOs (Saw/Tri/Pulse on 1 and Saw/Pulse on the other)
-1 Free running LFO (Tri and Square)
-2nd VCO can be synced to 1st OR external sync
-Very good tuning (<+/-4cents over 7(+) octaves)
-Very good temp stability (THAT320 + Tempco, though you can omit and use your own transistors and skip the Tempco)
-Triple thru-hole board stack - easy to build.
-No rare parts

Detailed Info:
MAIN PAGE
SPECS / BUILD DOCUMENTATION
BOM
SOUND SAMPLES

Here's what it looks like with a prototype FPE panel, but you will get a (nicer) laser engraved panel:




Here's the laser engraved panel:


And here are the 3 boards and panel:



--------

Currently not offering Panels/PCBs but I am working with a couple of vendors to offer those sets and possibly full kits. I will post on this thread with any updates.
ixtern
Very nice VCO and the price is reasonable.

But...I have some doubts regarding design:
- why pnp THAT320? pnp are always worse than npn and the choice is less
(for npn I can choose from THAT300, MAT14, LM394, AS394);
- why slow CMOS gate as comparator?
- why to use buffers from LM13700? If LM13700 is used without buffers, it can be replaced without any changes by LM13600, NE5517 (rare) or very cheap AK317DC (always nice to have wider choice). Maybe in this case buffers from 13600 (and others) may be used but it needs careful analysis I cannot make.

P.S. I am always in need of another VCO smile
SphericalSound
Cool sandwhich of waves
devinw1
Thanks, and I will try to answer your questions smile

1) PNPs for the Expo is simply because that section I used mostly from the classic EN129 Expo generator. Also most of the NPN expo designs seem to be set up to be a current sink rather than source but the Iabc pin on a LM13700 wants a current source so the dual PNP design is ready to rock.

2) I'm using the 40106 because it's super cheap and simple. Plus, I looked around and saw a lot of people making simple drone oscs out of it but no real VCOs so I wanted to try. It actually works quite well and left some open units to use as buffers and part of the sync circuit. In other words, why not? Mr. Green seriously, i just don't get it

3) Point taken. I actually don't use the LM13700 on the VCO B (syncable) channel. If I do a version 2 of this I'll just dump the buffers on VCO A and make it more flexable for OTA choice. In the meantime LM13700s are still plentiful and cheap, so hopefully not too much of a worry!
devinw1
MapacheRaper wrote:
Cool sandwhich of waves


Thanks! I loves me a good FR4 sammich! hihi
basicbasic
That documentation is SlayerBadger!
devinw1
basicbasic wrote:
That documentation is SlayerBadger!


Thank you!! I tried to up my game on that since the last project! It's peanut butter jelly time!
Low-Gain
https://modularaddict.com/wpa-2vl1osc-pcp

It's peanut butter jelly time! It's peanut butter jelly time! It's peanut butter jelly time!
jonny_w
Beauty! This is an auto-purchase for me, based on the INCREDIBLE quality of your Pro-One kit smile

Is there an issue with the BOM link? I can't seem to access it right now.
devinw1
jonny_w wrote:
Beauty! This is an auto-purchase for me, based on the INCREDIBLE quality of your Pro-One kit smile

Is there an issue with the BOM link? I can't seem to access it right now.


Woot! Thanks MA for getting that up so quick!

As for the BOM, it is working for me... Weird! Try to save the link and download the file, maybe it is an issue with your browser trying to open an Excel file?
jonny_w
devinw1 wrote:
jonny_w wrote:
Beauty! This is an auto-purchase for me, based on the INCREDIBLE quality of your Pro-One kit smile

Is there an issue with the BOM link? I can't seem to access it right now.


Woot! Thanks MA for getting that up so quick!

As for the BOM, it is working for me... Weird! Try to save the link and download the file, maybe it is an issue with your browser trying to open an Excel file?


It was indeed a browser quirk. Got it to work smile
devinw1
Oh good! thumbs up
mbizon
I love me some CMOS OSCs, and the demo sounded great!
I saw the MA pcb/panel but wondering if there are full kits selling anywhere?
devinw1
mbizon wrote:
I love me some CMOS OSCs, and the demo sounded great!
I saw the MA pcb/panel but wondering if there are full kits selling anywhere?


Not at this time but I will say the BOM is very complete and plug and play. You can get everything from Mouser and Tayda except the tempcos .
honeyb
devinw1 wrote:

Not at this time but I will say the BOM is very complete and plug and play. You can get everything from Mouser and Tayda except the tempcos .


Almost plug and play.. I'm wondering if the tempcos should be 3300ppm or 3500ppm?

Looking forward to building this, the kit looks awesome!
devinw1
honeyb wrote:
devinw1 wrote:

Not at this time but I will say the BOM is very complete and plug and play. You can get everything from Mouser and Tayda except the tempcos .


Almost plug and play.. I'm wondering if the tempcos should be 3300ppm or 3500ppm?

Looking forward to building this, the kit looks awesome!


Go with the 3300 Akenohms. I will get this added to the build doc/BOM soon too! Thanks!! Rockin' Banana!
honeyb
Just finished up the module. The build is straightforward, no tricks or issues. Really nice quality boards and panel, this is a quality product.

The only question mark was---- I had all knobs full CCW the first time I fired it up. No sound.

Because at full CCW, the oscillations are sub-audio. A quick wiggle and everything is good.

I'll post pictures later, now it's time to rack it and start playing. This is my first sync'able VCO, really not sure how best to use that feature. I guess I'll have to twist some knobs and find out!
honeyb
Just finished up the module. The build is straightforward, no tricks or issues. Really nice quality boards and panel, this is a quality product.

The only question mark was---- I had all knobs full CCW the first time I fired it up. No sound.

Because at full CCW, the oscillations are sub-audio. A quick wiggle and everything is good.

I'll post pictures later, now it's time to rack it and start playing. This is my first sync'able VCO, really not sure how best to use that feature. I guess I'll have to twist some knobs and find out!
honeyb
Because its a dual VCO, that's why!

if you are wondering about the dual post.

No fat-fingering on my part, no sir-ee bob!
devinw1
Double VCOs, double posts! lol

Thanks for the post! I'm glad it went well for you! Yes, the coarse knob has a very large swing, mainly so you can drag it to a large range of pitches even if your device (Say a beat step pro) is defaulting to output a CV like 5V... But this means if you have no CV, you can turn it down to reaaaallllyyyyy slow and not hear it. w00t

For sync, try using an envelope to FM the sync'd osc in unison with OSC a. There are other things you can do too of course.
honeyb
devinw1 wrote:
Double VCOs, double posts! lol

Thanks for the post! I'm glad it went well for you! Yes, the coarse knob has a very large swing, mainly so you can drag it to a large range of pitches even if your device (Say a beat step pro) is defaulting to output a CV like 5V... But this means if you have no CV, you can turn it down to reaaaallllyyyyy slow and not hear it. w00t


Lots of positives to a large swing on the coarse knob, you can always use the fine knob for fine adjustments.

devinw1 wrote:

For sync, try using an envelope to FM the sync'd osc in unison with OSC a. There are other things you can do too of course.



Appreciate this tip. Actually, I'm really not sure what the rest of the controls do. Could you confirm/deny/illuminate my guesses?


The switch at the top-- When far left, VCO A is synced to VCO B, i.e. every time VCO B starts a new cycle, VCO A resets. Switch in the middle position, no sync (the two VCOs are independent) when far right, VCO B syncs to VCO A. Yes?

"coarse" and "fine" adjust the basic tone, CV can modulate this. Two modulation routes: 1 v/octave jack raises the tone, where 0V CV input is whatever the coarse/fine knobs have tuned it to?. The FM input jack additionally modulates frequency? With the FM knob attenuating the signal??

Pulse width is set with the PW knob, totally CCW giving 50% duty cycle on the square wave. Turning the knob increases the duty cycle to a max of circa 90%?. Additionally, control voltage from the PWM input can modify the default setting, with the PWM knob attenuating the amount of modulation?

I know what pulse width does to a square wave, basically the duty cycle. I don't know what it will do to the triangle or sawtooth-- partially because I don't know if this beast is a square wave core (I suspect so, given the heart is a 40106) or triangle core.

Gave my unit Swedish colors. Racked it ans started playing before I thought about taking shots of the build/internals. Couldn't wait to hear it in action!

The triangle is really sweet, nice clean tone. Plenty of roughness/harmonics on the other waveforms if you want it. Built is straightforward. Takes a little while given the three boards, but not difficult.

[/img]
devinw1
honeyb wrote:

Could you confirm/deny/illuminate my guesses?


The switch at the top-- When far left, VCO A is synced to VCO B, i.e. every time VCO B starts a new cycle, VCO A resets. Switch in the middle position, no sync (the two VCOs are independent) when far right, VCO B syncs to VCO A. Yes?

"coarse" and "fine" adjust the basic tone, CV can modulate this. Two modulation routes: 1 v/octave jack raises the tone, where 0V CV input is whatever the coarse/fine knobs have tuned it to?. The FM input jack additionally modulates frequency? With the FM knob attenuating the signal??

Pulse width is set with the PW knob, totally CCW giving 50% duty cycle on the square wave. Turning the knob increases the duty cycle to a max of circa 90%?. Additionally, control voltage from the PWM input can modify the default setting, with the PWM knob attenuating the amount of modulation?

I know what pulse width does to a square wave, basically the duty cycle. I don't know what it will do to the triangle or sawtooth-- partially because I don't know if this beast is a square wave core (I suspect so, given the heart is a 40106) or triangle core.


OK, let me try and answer your questions grin.
1) VCO B (the right one) is the one that can be synced to something. If the switch is in the middle, it is just like VCO A and independently controlled. If it is to the left, VCO B will be synced to the freqency of VCO A. If it is to the right, it will be sync'd to whatever is plugged into the sync input (so this would be for if you have a separate VCO you want to sync VCO B to.

2) Yes, the coarse and fine tones are just going to the CV summing of the exponential converter. The 1 V/oct is your typical CV for a VCO to control pitch. Every additional volt to that jack will double the frequency (ie one octave). The jacks are wired so that VCO B's 1 V/oct control is just a copy of VCO As. As soon as you plug in another 1 V/oct CV to the right side jack, this takes precedence and now VCO B is being controlled by this CV. This is why the right side V/oct jack is in parenthesis. Correct on the FM. Each VCO has a LINEAR FM input (note the 1 V/oct jack we talked about is an exponential). The FM pot does indeed attenuate the input from 0 to 100%.

3) PW is for the pulse width of each pulse output (note there is no dedicated square output). With the knob in the middle, you will be at 50% duty (a square wave). Full CCW and the PW gets narrower and narrower and actually will go to zero and you hear nothing. Same with full CW but opposite. The PWM input allows you to have a CD modulate the PW and yes it is attenuated by the pot just like the FM.

Btw the VCO is indeed triangle core, but it does technically have a fixed square coming out of the core, but I didn't put a jack for this because well...there's only so much space smile, and you can get a square that's good enough just by using the pulse output and selecting the middle position.

Hope that helps! Guinness ftw!
honeyb
devinw1 wrote:

Hope that helps! Guinness ftw!


Sure does! All questions answered, thanks for the awesome support!
devinw1
Not a problem! thumbs up thumbs up
wendallsan
honeyb wrote:
The only question mark was---- I had all knobs full CCW the first time I fired it up. No sound.

Because at full CCW, the oscillations are sub-audio. A quick wiggle and everything is good.


Haha! I built two of these and did the exact same thing! It took me 2 days to finally turn a knob and realize! Always fun to be troubleshooting a circuit with no problems to find!

I think I'm going to build 2 more for a quad complex oscilltor bank in 2 rows of 54hp:

(Edit: I confused Mutable Warps with Streams)



What would you put into that remaining 8hp, assuming I can get power into the case some other way?
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