How to mod Nicolas LFOs to Synch

MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

Hi,

Im using this 2 homemade Nicolas3141 LFOs and they work nicely, but I would want to mod it so I can reset/synch them.

I guess I have to discarge the cap when the gate/trigger is up, isn´t?

Any suggestion of how to do it?

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gabbagabi · Posted: Sat Sep 29, 2018 2:29 am Post subject:

kind of,
when u shortenig the Integration cap, the wave will restart at the 0V line,
i guess for many a "real" sync would mean that the wave starts below zero,
in the end it up to you

may the pic will make it clear

edit: i have an idea will post it later, have to clean da houze first Smile

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MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

At 0 is perfect.

The question now is how do I short the cap with a gate/trigger easy peasy way? Smile

Maybe the gate is connected to the base of a transistor, and the colector and emisor are shorting the cap?

If the cap works in bipolar fashion I would need 2 transistors, 1 NPN and one PNP... isn´t?. But then, the gate would only activate one of the trannies... hmmm

gabbagabi · Posted: Sat Sep 29, 2018 4:39 am Post subject:

well if zero is good,
try something like this,
keep in mind it is only a simulation

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gabbagabi · Posted: Sat Sep 29, 2018 4:57 am Post subject:

i found an old simulation on the harddisk searching for "nicolas",

the theory here is: if u apply an offset to the comparator --> u could make the signal unipolar, if u sync this - u sync the right way

to make it bipolar again u would need an other op-amp, which also could bring u closer to the 10Vpp

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MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

Thanks for taking the time to explain and simulate it.

Im not sure why an opamp is needed at the gate´s in. To keep things simple couldn´t work just a 100k resistance to the base of the transistor?

So gate in>100k R>base tranny>which shorts the timer cap

I have the circuits in tiny PCBs that can´t allocate another opamp Wink

Ricko · Posted: Sat Sep 29, 2018 11:52 pm Post subject:

Semi off topic. For another approach, search for my old post on "Kick Sync" which can add synch to any VCO because it works externally.

gabbagabi · Posted: Sun Sep 30, 2018 1:19 am Post subject:

hey Ricko, i was about to mention the kick sync yesterday, but somehow lost it Shocked

MapacheR. if you would be ready to solder a second little board it could look like this, dont forget to breadboard it before, cos i only simulated it. if it is working as a whole, may C3 must be higher value

the reason for the extra opamp is that the sync impuls needs to be rather strong (rail to rail). with the extra opamp u could use almost any signal as a sync source

what u have planned to use as sync signal?

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PHOBoS · Posted: Sun Sep 30, 2018 2:09 am Post subject:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

gabbagabi · Posted: Sun Sep 30, 2018 5:27 am Post subject:

poser! posting something that is called "super concert" to the nicolas lfo Very Happy

MapacheRaper, if there is to little space to make additions, why do not leave the circuits as they are, make a nice frontpanel for them. These are maybe one of the first circuits that u have build, may it is nice to keep them original, some modulators will be always handy.
In fact u will miss more in the future like sinus and inverted ramp, the triangle out is not buffered, the signal is not 10Vpp.

And then start building something more complete and leave a little more space?

or, make a more complete daugther board where u include all this, with a little help from ur friends here?

MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

Wow, thanks for all the suggestions, Guys!.

@Ricko. How to add sync to a VCO was one of my next questions... Im digging it. Thanks!!

@Gabba. That miniPCB seems superfeasible. I will try it. I prefer to update the circuits that to left museum reliquics Wink

. I plan to sync with standard 5v gates (does it mean I can use just the gate>100K resis>base transistor> that shorts timer cap?). Aanyway I´ll try both, I guess. Danke, maestro!!

@Phobos, thanks for the circuit. Im studing it Wink

.

gabbagabi · Posted: Thu Oct 04, 2018 4:32 am Post subject:

please test it before on breadboard and let me know if it works, may u need to raise the value of the cap to lets say one or two nF

and, eventhougth i repeat myself, u will miss more in the future like sinus and inverted ramp, the triangle out is not buffered, the signal is not 10Vpp

may u consider a bigga daughterboard whith a quad-o-pamp?

PHOBoS · Posted: Thu Oct 04, 2018 11:22 am Post subject:

excuse me for dropping the schematics without any further explanation, I had a bit of a cold (actually still do). The first one was
designed for the EK2100 and works on a dual supply. You can find more info about that one here. The second one is part of a modified
"Super Concert" toy keyboard which works on a single supply. I only posted that one for the part in the top right corner and you can
find some info about it here.

They both use a LFO similar to the nicolas one to which I added different gating options. The top (EK2100) circuit uses a switch to
choose which gating option but the LFO section is a bit more complicated because of the dual supply. The other circuit uses a mux
which makes thing look a bit more complex but the LFO is more recognizable. Both of them are controlled through the non-inverting
input of one of the opamps. I don't think this method will be useful for syncing, but maybe you can do something similar with the
inverting input of the opamp that the capacitor is connected to (the integrator). g.gabba's method of directly shorting the cap might
work better though.

Anyway, it reminded me of those two circuits so maybe you'll find something useful in there Wink

MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

I only grasp the surface of what you say, but I find it fascinating. Studing the circuit and your words will bring a lot of new electronic understanding and new ideas... Thanks for your explanation, Phobos!!

@Gabba. I have been building a Rampage and it works!!!. Fuck yea!!. Im overblown with the possibilities... So I haven´t had time to develop the board yet, but I will try in some moment and report, dude Wink

Thanks!!

gabbagabi · Posted: Wed Oct 10, 2018 5:54 am Post subject:

take a deep breath and relax Smile

did the Sync-circuit has worked on breadboard? and now u are going on to build the daugtherboard?

Well may u would consider something more phuture proof?
like this?

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MapacheRaper · Joined: Feb 15, 2018 Posts: 166 Location: Spain

This forum has few users but top quality ones... You have done a full-on LFO here.

That will be my next LFO build for sure.

I like how it exudes that is a labor of love... How much time did you employ?. Did you study EE?

In any case I think you should totally post it in the official nicolas LFO thread for more users to find it.

Thanks!!