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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
G2 analog CV/Gate Output Mod
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3phase



Joined: Jul 27, 2004
Posts: 1182
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PostPosted: Mon Oct 19, 2015 2:42 am    Post subject: G2 analog CV/Gate Output Mod
Subject description: just mentioning the successful hardware mod of my G2
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Hi, just wanted to mention the realisation of a CV/Gate output mod for my G2. After working for quite a while with DC enabled outputs my demand grew to have a wider cv range and also to be able to trigger older synths that require more than the 3,5v the G2 gives out max.. It also has pissed me off that i needed 2 valuable G2 outputs just for one simple CV/gate combo.. With a little extra electronics i was able to do that with a single channel now..and more..but i am still working on that. I decided to keep the G2 internal Mod simple.
Just 4 extra mini jacks for standard analog synth interfacing. And all the extra tricks from an external box.. that interfaces with the dedicated CV outputs.

This little mod gives me 2 cv outputs that give a 7 octave range, with internally adjustable offset, and 2 gate out, internally adjustable from 5v to 10 volt .

Using the Outputs C and D of the G2 for that.. So that Outputs cant be used for Audio when being used as CV control channels.

Also the gate goes high as soon a voltage higher than 0V is generated on the output channel..so CV and Gate are not independent from each other, but a neat little trick to control on external monophonic synth voice with just one G2 output.


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dorremifasol



Joined: Sep 28, 2006
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PostPosted: Mon Oct 19, 2015 3:48 am    Post subject: Reply with quote  Mark this post and the followings unread

This is awesome. Thanks for showing!

I'd really love to implement this solution in my G2. I'm very curious about your gate output solution.
If I understood well, a circuit raises the gate output as soon as anything other than 0 is sent thought a CV output. Does that mean that it can only work with sounds that don't have a decay after being released? I mean, the CV output should be 0 to make the gate output be 0 as well.

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3phase



Joined: Jul 27, 2004
Posts: 1182
Location: Berlin
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G2 patch files: 141

PostPosted: Mon Oct 19, 2015 4:41 am    Post subject: Reply with quote  Mark this post and the followings unread

thats the drawback..works only on notes without release phase..which you have on monophon analog synth sequencing and basslines quite often.. or you use as before one channel for the pitch and the other for gate.. the extra gate outputs are anyway good for me since i needed higher gate voltages to trigger an arp.

I am working on a solution to multiplex the cv outs.. but only have 5 cv outs with a 1 ms refresh rate working yet..on a board thats to big to fit inside the g2..current draw with under 20 mA probably still ok.. so might become an internal solution at one point. But i think a can double or tripple that with better circuit design.. or, what would be better, do that 5 with a single channel.. However..since such solutions need dc interfacing with the g2 i ve put 2 simple real dc outputs on my g2 now. The solution with the removed caps was a bit to limited, could´nt trigger the arp for example. Thats the better solution.. have a basic DC 2 channel out..and do the demultiplexing with an external box that is still in development.

The electronics for the demultiplexing would anyway only fit inside the G2 with a professional manufactured circuit board.. I am thinking about that..but the market for such a mod would be probably to little..

In any case thats just step one.. i got too much fun with the g2 as sequencer for real analogs already.


The other way around is probably interesting too. It already has a gate and cv input in form of the footswitch/pedal jack..
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Blue Hell
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Joined: Apr 03, 2004
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Location: The Netherlands, Enschede
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PostPosted: Mon Oct 19, 2015 6:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice build :-)
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also .. could someone please turn down the thermostat a bit.
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Jack_Hertz



Joined: May 14, 2010
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PostPosted: Mon Oct 19, 2015 1:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very nice! Would this be cheaper / easier / better then using a Kenton MIDI to CV box?
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varice



Joined: Dec 29, 2004
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PostPosted: Mon Oct 19, 2015 10:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool

Nice work Exclamation

What external synths are you controlling?

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varice
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varice



Joined: Dec 29, 2004
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Location: Northeastern shore of Toledo Bend
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PostPosted: Mon Oct 19, 2015 11:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

dorremifasol wrote:
...If I understood well, a circuit raises the gate output as soon as anything other than 0 is sent thought a CV output. Does that mean that it can only work with sounds that don't have a decay after being released? I mean, the CV output should be 0 to make the gate output be 0 as well.

3phase wrote:
thats the drawback..works only on notes without release phase...

It seems to me that there may be a fairly easy solution for DIYers in this case if you only need AR EG(s). While using the G2 CV output for pitch control only (not for a gate), an external circuit could be designed that would detect note changes (slightly more than one semitone up or down) to generate a trigger signal for the AR EG(s). This would allow the release phase of the EG(s) to play out until the next new note value is detected.

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varice
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3phase



Joined: Jul 27, 2004
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PostPosted: Fri Oct 30, 2015 3:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

yep..good idea pitch change as trigger.. However for the cv gate output for the g2 thats too much hassle for me since i want the direct ports on the g2 universal plain dc out.. the two extra gate jacks are mainly for clocking.. they give me the running status while the out above delivers clock ticks.. since the offset internally is variable i ve set it in a way where the actual gate triggering is happening within the negativ voltage range what allows the main cv output to deliver clean 0-5 v clock pulses ..but the whole setup can be used as pseudo gate for short sounds too. and the whole thing is prepared to get two extra holes and become a 5 cv out plus that pseudo gate / running status jack on a single audio channel..so just channel D for cv control


So as mentioned before..that is just the interim state or interface to the de-multiplexing device im just building that shall give me 5 independent cv outs and a clock with running status on a single G2 output... so 7 jacks..on two channels = 14 jacks..
Since i dont want to drill that many holes into my g2 i will realize that in an external box with own power supply.. An internal solution would be thinkable too..but big question than..

how much extra current draw can the internal power supply take?
Since the power transformer gets already quite warm on the expanded g2 that might be quite limited..

Any ideas or suggestions how much extra current one might be able to steal from a g2 power supply? Is the power supply of the G2x bigger than the one for the standard g2? If not the internal supply might take a little extra load. However.. for now i keep any extra circuit outside of the G2

And the synths this is supposed to sequence is mainly an arp avatar and an oberheim sem module.. booth actually capable for duophonic osc control.. so with filter and gate each in need for 4 cv´s.. So my project is not as over sized as it looks on the first hand.. i prepare for 5 cv´s to have an spare option cv and to allow me if it gets tight with the process timing to reduce to 4..

and the extra clocking outputs are just to use the short timing intervals in between the cv transmissions to smuggle some extra info.. I ve use for din sync output of a g2.. i tried that allready.. ther are fun things to do when the G2 controls the clocking of an 808. However that clocking ports might be left out too when theymake to much problems.. main goal is to achieve 4 independent cv out on one g2 audio output with a timing resolution of max 1 ms.. but targeting 0,5 ms .. should be better than what midi can do..

Thats actually another reason that i split the project in 2 stages.. so i still keep the high resolution single CV per audio output version when needed and the extra box with multiplexing related timing and resolution flaws for standard operation with cv hungry synth modules. i ill see how that goes during the winter..
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varice



Joined: Dec 29, 2004
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PostPosted: Sun Nov 01, 2015 11:05 am    Post subject: Reply with quote  Mark this post and the followings unread

3phase wrote:
...how much extra current draw can the internal power supply take? Since the power transformer gets already quite warm on the expanded g2 that might be quite limited...

...Any ideas or suggestions how much extra current one might be able to steal from a g2 power supply? Is the power supply of the G2x bigger than the one for the standard g2? If not the internal supply might take a little extra load. However.. for now i keep any extra circuit outside of the G2...

Just my opinion, but I’m not very impressed with the G2 power supply. In my experience, my G2X is overly sensitive to even minor dips of the AC mains voltage, causing it to reset. If I recall correctly, this has also happened with my expanded G2 Keyboard. So this would suggest that there may not be very much headroom for any addition current draw.

I haven’t opened up both of my G2s to compare the power supplies, but I doubt that there are different ones used in the G2 Keyboard and G2X. There is not that much difference in electronics load between an expanded G2 Keyboard and a G2X to make that necessary.

3phase wrote:
...And the synths this is supposed to sequence is mainly an arp avatar and an oberheim sem module.. booth actually capable for duophonic osc control.. so with filter and gate each in need for 4 cv´s.. So my project is not as over sized as it looks on the first hand.. i prepare for 5 cv´s to have an spare option cv and to allow me if it gets tight with the process timing to reduce to 4...

An Avatar and a SEM driven by a G2… Cool That must fun…

Looks like a good project to get a multiplexed CV output, best of luck with that. Let us know how it goes!

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Oli



Joined: May 21, 2008
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PostPosted: Fri Nov 06, 2015 12:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice work!

3phase wrote:
... Since i dont want to drill that many holes into my g2 ...


How about a single drill hole, with a multi-pin socket, for break out cables? Never as nice, but much easier metal work.

3phase wrote:
... how much extra current draw can the internal power supply take?


How about tapping off the mains lines, pre-transformer, and using an internally mounted encapsulated power supply? RS used to do really nice supplies; compact, high spec, reasonable cost. Not sure if they still do.

Is there enough room for everything in a G2?

PCB prototypes are not overly expensive these days. If you're reasonably confident with your schematic, it can save a lot of development time to have the board made for you. Neat layout, SMT, and ground planes/vias can solve some issues too.

BTW, are you an engineer?

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