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LZX Cadet VCO layout DIY
MUFF WIGGLER Forum Index -> Video Synthesis  
Author LZX Cadet VCO layout DIY
FetidEye
Hi

I'm making layouts of some of the LZX Cadet modules, with Eagle.

As learning examples, I've succesfully made the C10 Multiplier and the summing mixer.
(pcb's made and tested)

Now I'm working on the VCO.

Does anyone know what the net name "U7_+IN" means?

There is no U7 IC, so it might be some old identifier.
There are 2 nets with this name, the output of the cd4066 (pin 9 goes to R8, then to the net name)
and at R25, near the VCO_CORE_BUFFERED net.

The "+IN" part sound like it must go into an OPAMP.

It might be enough that these 2 nets are connected, but I want to be super certain!

If I have some room left, I want to make extra outputs, rising and falling SAW waveforms, which are super useful.
And maybe some more stuff, if I can find something useful like an inverted TRI / SQ, or some voltage normalled to the CV input so that the VCO goes lower by default.
vonkhades
FetidEye wrote:
Hi

I'm making layouts of some of the LZX Cadet modules, with Eagle.

As learning examples, I've succesfully made the C10 Multiplier and the summing mixer.
(pcb's made and tested)

Now I'm working on the VCO.

Does anyone know what the net name "U7_+IN" means?

There is no U7 IC, so it might be some old identifier.
There are 2 nets with this name, the output of the cd4066 (pin 9 goes to R8, then to the net name)
and at R25, near the VCO_CORE_BUFFERED net.

The "+IN" part sound like it must go into an OPAMP.

It might be enough that these 2 nets are connected, but I want to be super certain!

If I have some room left, I want to make extra outputs, rising and falling SAW waveforms, which are super useful.
And maybe some more stuff, if I can find something useful like an inverted TRI / SQ, or some voltage normalled to the CV input so that the VCO goes lower by default.


yup its weird...



so I guess is just an old idenifier maybe the U7 got removed and the connection tag/label was not updated... looks like in this picture is for the buffer of the output.

BTW do you think would be possible to hack/modify the official pcbs to got those outputs you mention? I would me amazing to have ramps in addition to the triangle and square that we already have.[/img]
vonkhades
I guess you already know, but just in case.. buffers are widely used on signal outputs of modules so for instance voltage doesnt drop if you stack bananas/minjacks or/and to bump up signal.
FetidEye
So it might have to connect to +in of U1 (or U20?), you think?

Going to test this with a multimeter, I have 4 VCO's in my rack, so I can check this realtime.

If you patch the TRI out to a Fader input and the SQUARE output to the CV input of the Fader, you will achieve the Ramp waveforms.
So I was thinking to strip down the Fader circuit and add it to the VCO layout.
The two Fader pots are not needed, so that saves space.
FetidEye
A global test shows that R8 and R25 are connected, but I can't find more connected points (no IC's or resistors)

w00t The layout is done, hardcore routing on this one!
I've added a SQ output.
No room left for the ramp circuitry + outputs, going to make an external PCB for this.


if anyone has a picture of a bare VCO PCB, that would help !
(with all those resistors covering my pcb's, it is hard to pinpoint locations~)
smrl
Yeah, that net is connected to R8, R25, C18, and pin 2 of 74HC14 (U12). Nothing else.
FetidEye
ok, thanks. screaming goo yo

note: I think you meant pin 3 of 74HC14 (U12.2) ?
(12.2 = 2nd inverter, pin 3 and 4)
smrl
yeah, I did mean pin 3. Sorry about that smile
vonkhades
So I found some space on the panel and added the jack for the square output! Its lovely.



FetidEye
Yeah, that squarewave is highly useful.

I've made the pcb layout for the ramp expander now, just have to order the pcb's.
I've added the squarewave output on the same place as you (but pcbmounted)

offtopic: cool, those O&C units. how do you use them for video?
I'm building one of those too soon, we are going to do a groupbuy with some friends..
vonkhades
FetidEye wrote:

offtopic: cool, those O&C units. how do you use them for video?
I'm building one of those too soon, we are going to do a groupbuy with some friends..


I use the quadraturia mode which is a quadrature lfo with a tons of options.

The otherr app I love to use is the app similar to "Turing machine" by music thing... This app is awesome for animation when you have triggers from bassdrum or a sensory translator so you shift the scene a lot when the trigger ocurrs.



The ping pong app is cool with LZX navigator you can do a very nice model of an object bouncing, and the lorenz attractor app also is interesting.

The cool thing is that you have so many options on a single module.. It's like a metamldulator, also you can adjust offset and output range by software so you don't need a bridge or scaler to convert from 5v to 1v
vonkhades
BTW any ideas or suggestions on how to add a FINE tune pot to the VCOs?

I'm having a lot of troubles to run them unsynced and make them look like a slow scrolling....


I also tried the SINE+SQUARE->FADER to get a RAMP.. but its a poor mans RAMP definitely since its weird shaped it doesn't look like a regular ramp like, but rather like a 1 phase RAMP and then 0V so its not continues... like if the ramp has been compressed to the 50% and this is obviously because the fader is chopping the "falling" part of the sine wave and its converted into 0v.
FetidEye
still, better than no ramp in my opinion.
maybe it is possible to scale it up again. I have to try that.

I want to try multiturn pots on the VCO for finetuning.


I replaced the pots on my Gieskes OSCope with multiturns, that worked like a charm!
vonkhades
FetidEye wrote:
still, better than no ramp in my opinion.

Completely agree!

FetidEye wrote:

I want to try multiturn pots on the VCO for finetuning.

I replaced the pots on my Gieskes OSCope with multiturns, that worked like a charm!


Keep me. Informed plz.
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