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3TrinsRGB+1c triple VCO
MUFF WIGGLER Forum Index -> Video Synthesis  
Author 3TrinsRGB+1c triple VCO
Hi everyone.

Let me first say that I am not a forum wizard by any means, and I apologize if I mess up any posting protocols while attempting to share and update this thread.

I have been tinkering with an add-on VCO circuit for the 3TrinsRGB+1c video synth. The VCO circuit is built around the cd4046 ic and gets up into the MHz frequencies. Importantly, it is hard-syncable to Hsync and Vsync signals from the 3Trins (I have opted to use an LM1881 to strip the sync signals from 3Trins video, even tho the signals can be tapped internally). I made 3x of these for myself on some protoboard, and they are very fun for extending the 3Trins. After realizing there was some interest on the 3Trins FB forum, I am planning to try to make some PCBs. This would be my first attempt at doing something like this.

Currently, the plan is for a board that supports 3x VCO's and the LM1881 – all powered from the 3Trins headerbay. The LM1881 would have 6 headers (3x for Hsync and 3x for Vsync)... Each VCO would have dedicated headers for sync input, CV input, and VCO output.

I am trying to gage interest from folks here regarding such a "module". If I can get my act together to make a viable "plug-on" PCB... are any of you tentatively interested? I'll post some video links soon to entice, and I will update with any progress.

I'd be interested. It's a great little synth.
count me in!
I'd be interested as well!
count me in too please
count me in.
question: does this really work on the power from the patchbay?
it / (mine) only outputs 2.6 volt and the LM1881 needs 5-12 volt (says the spec sheet)
sign me up smile
FetidEye wrote:
question: does this really work on the power from the patchbay?
it / (mine) only outputs 2.6 volt and the LM1881 needs 5-12 volt (says the spec sheet)

Works on mine. I'll make a video tonight and post to show. I will also measure my header output for comparison. If I make these, I could send you one to try first, too. It also will 'sync' to other sources (like lfos or RGB outs) without the LM1881, but then it partly defeats the purpose.
if you need help with the layout or pcb order, let me know
For those interested, the circuit is quite simple.

The following I learned while reading about the Thomas Henry 4046 VCO built around the cd4046 ic:

The CD4046 ic has a built-in VCO (that reaches up into MHz frequencies) and was designed as a PLL with two different types of phase comparators. One of the phase comparators acts effectively as an XOR gate. The ic also has an "inhibit" pin that stops the VCO, and when the VCO starts again its phase is reset... so the VCO can be easily hard-syncd by chaining these features. This is critical for video VCO, so that the signal canock to line and frame tracing sync signals, allowing it to generate stable lines/patterns. The fact that it can be controlled by CV outta-the-box makes it great!
count me in, too, please!
thumbs up
Me too! Eurorack config/panel too!?!?!

Here is a link to a video example of 1x 4046 VCO with the 3TRINS.

I have made a breakout for the 3Trins header bay, and I am using that for patching. Power is coming from the breakout-bay (so from 3Trins headers) goes to the breadboards that have the 4046 and LM1881 (and an inverter) on them.

At very first, I am trying to demonstrate that the color channels are all the way turned down on the 3Trins. Next, I am just showing the signal unsync'd in different channels. Then I plug in the Hsync signal from LM1881 and adjust frequency and dial in some CV from a mixer off camera. The rest is just some noodling. For most of the remainder of the video, the CV source is the 4MS PEG, with the channel being "ping'd" by the Vsync from LM1881... which allows it to make somewhat frame-stable patterns/modulations. Near end of video, I unplug from 4MS and switch to one of the 3Trins LFOs

I didn't have time to plug in all three at once tonight, and I figured this was at least good for showing that sync works from the LM1881 powered off headerbay.

I will post more videos soon on less busy nights.

A couple more video links here. These show using an 8-step sequencer and 1x 4046-VCO (sent to Red channel on 3Trins). It is fun when the sequencer is clocked at audio rates. One video is just noodling with the sequencer, and even 'syncing' the sequence crudely with the Vsync sent to the RESET on sequencer. The other video is the sequencer and a digital oscillator mixed together. The oscillator is the Pittsburgh Modular DNA symbiotic waves ('MIX' output)... makes fun patterns and has fine-tune so can sorta dial in some fun stuff. There is some horizontal noise (most obvious at very beginning) in the second video that seems to be related to the DNA's signal going through the CV mixer.

Just sequencer noodling (no audio to hear):

Sequencer + DNA Symbiotic Waves:
@drumasaurusrex this is great!
drumasaurusrex wrote:
FetidEye wrote:
question: does this really work on the power from the patchbay?
it / (mine) only outputs 2.6 volt and the LM1881 needs 5-12 volt (says the spec sheet)

Works on mine. I'll make a video tonight and post to show. I will also measure my header output for comparison. If I make these, I could send you one to try first, too. It also will 'sync' to other sources (like lfos or RGB outs) without the LM1881, but then it partly defeats the purpose.


I just tested the 4046 on 3trins power, that works fine .
I couldn't get the 1881 to sync the signal though, maybe i'm doing it wrong.
do you use the sync output/input (RSin) from the 3trins or the Rout to get the sync to the 1881?

and pin7 from the 1881 directly to pin14 of the 4046?
I use the actual composite video from 3Trins, the onboard sync signals (Rsin, etc) never worked for me either.

As for the wiring... Pin14 on 4046 gets wired to whatever sync you are using... so if want Hsync from LM1881, that is pin 1 "composite sync". If going straight from LM1881, then pin3 on 4046 needs to be held high. I had these wires up originally for VGA sync which is opposite polarity (and I have pin 3 on 4046 grounded), so I am using an inverter 4069 to invert the sync.

This is how I soldered them up to use with a VGA synth I was making. For this to work with 3Trins, you either want the opposite polarity in wiring of pins 3 and 14... or you want to invert the composite sync signal (which is what I am doing for now because they are all soldered up already). In next week, I am going to breadboard the whole "module" I am planning, and I will try to document it here and show how goes. I am probably going to change the circuit slightly, but this cartoony schematic might get you up and running to play around.
Count me in too.
Love anything that expands on the fantastic 3trins!
Wooo! Count me in ~ would love to see the circuit...
feel free to PM me if / when something is ready to go.
i will see the message even if i don't see the new posts here.
Definitely interested in this!
Hey all.

It has come to my attention that the 3Trins "High" voltage level is different on different units. Mine gives over 4v, others give under 3v. I've heard that 3.3v is about standard. I am going to pause and try to get some more specifics. The cd4046 max frequency is notably sensitive to these difference is voltage levels, and can cause a big change in the number of vertical bars you can get at max V... at 4.3v (which mine gives) I get 20-30 bars depending on the cap values I've been trying out. But below 3v, it is not as fun.

I previously debated making the 3Trins version of this 3xVCO as a battery powered (9v) version with a buffered and limited amplitude. What do you all think about that? Then, there would be a consistent supply voltage to the ic, and I could set the output level... but if I went that route, I'm not sure if that output should match the *lowest* possible "HIGH" output that someone's unit might have... or the "average" (~3.3v)... or what?

So, I will try to figure out the range of voltage outputs and see what works.

In the meantime, how do people here feel about a battery-powered version?
It would mean using 2 fewer jumpers, which might be nice. smile
maybe everyone can measure what is the output. then we know the average.

a battery powered device is no problem for me.
Best to get the most out of the oscillators, it will be a more useful addon then
yeah, likewise -
tell me where to measure and I'll let you know.

battery power sounds fine, too.

set your multimeter to DC
you can expect voltages between 2.6v and 4v, so set the meter to that range
(on most meters this is '20')

measure between HIGH and GND

I get 2.6v
where abouts am i measuring?
on the output jack?
on the patchbay header
I'm reading just under 4.3v.
my VJ friend measures 2.53v (3trinsRGB from kit)
my 3trinsRGB is also a diy kit
2.58v from a kit
Mine was around 2.5v, built from a kit in August. I'll post a more accurate reading when I can.
sign me up
measured mine, was a kit (panel number 13): 2.52v
Bit late to the party, but please sign me up too! I'll try and measure my voltage when I get a chance. I'd be OK with battery power if necessary..
I'd be into this too if there's still room! Battery or not, it sounds awesome either way.
Checked on my scope and got 4.36v

I have a plan. It'll be a little bit before kits, but thanks to everyone's feedback the path is clear.

I'll post when some more progress.
Count me in! smile
me too, please PM when you have something I'll come back to this thread anyway smile
any news? would love to join the plan!
Tajnost wrote:
any news? would love to join the plan!

Glad to hear you're interested!
I very recently (week ago) rekindled some work on this after a handful of major life changes (baby, relocation, new job). I think the most likely way for me to move forward on this is with a couple revamps. The previous plan was to use 3 4046 PLL ics wired as syncable VCOs... with an LM1881 to extract sync from the 3Trins (so that folks wouldn't have to tap the onboard one). What I am currently imagining is a couple chicklet circuits – like mini modules: [1] video-sync'd VCO circuit (can add as many as like) – possibly 2 flavors in mind, one based on a 4046 and another with multiple entangled oscillators based on one 40106 ic... these could be configured to work with other setups such as LZX gear and not only for 3Trins tho 3Trins is my main interest; [2] an LM1881 chicklet for stripping sync; and [3] a video-sync'd stepped-CV sequencer that allows dialing in stepped modulations for pattern generation from the external oscillators or the oscillators onboard the 3Trins. The oscillators and sequencer would require a sync signal from 3Trins... if a person felt like tapping the onboard one, they could go that route... otherwise use an LM1881. I am still figuring this out. In meantime. I will post some proper schematics soon.

interested too!
Just finished building the kit from Gieskes so I'm interested as well smile
Hey did you ever get around to the PCB?? Very interested!
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