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 Forum index » DIY Hardware and Software
Mixing GATES and TRIGS
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Mon May 14, 2007 3:22 pm    Post subject: Mixing GATES and TRIGS
Subject description: of a step sequencer.
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What would be the simplest and best way to "mix" gate signals ?

not a stupid multi jacks ? (strap between multiple outputs...)

I consider only positive voltages and only one active signal (step outputs of a sequencer)

This would work ?

with all 47k ? and another tied to ground ?


gates.jpg
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gates.jpg


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Adam-V



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PostPosted: Mon May 14, 2007 4:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

A diode "OR" gate is what you need here.

Have a look at the diagram on the top left hand side of this page. You just connect a diode for each of the gates you require to be mixed.

Cheers,
Adam-V
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Scott Stites
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PostPosted: Mon May 14, 2007 4:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Diodes are actually a pretty good way of mixing gates and triggers - each signal goes to the anode of a diode, with all the cathodes connected together.

That's how I mixed signals in the Klee gate bus - I just tied the diodes to the input of a Schmitt trigger CMOS device to give everything a bit of snap - wouldn't necessarily be required in this application.


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Scott
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funkyfarm



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PostPosted: Mon May 14, 2007 10:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Okay !

And with diodes, what happen if accidentally two +10V p-p are present at the same time ?

Boum ?!
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Adam-V



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PostPosted: Tue May 15, 2007 2:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Diode logic circuits don't operate the same way a mixer or summing circuit does in that the input voltages are not actually summed together. A two input OR gate, for example, with a 10V signal at each input will still only put out 10V (actually it would be closer to 9.3V allowing for the 0.7V drop across the diodes).

So no boom if two 10V signals are applied to the inputs.

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Adam-V
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fonik



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PostPosted: Tue May 15, 2007 6:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Adam-V wrote:
...(actually it would be closer to 9.3V allowing for the 0.7V drop across the diodes)...

you could alleviate this effect using schottky (BAT38) or gemanium diodes, i guess (about 0.3V voltage drop)? could be important if you use lower gate levels...

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Scott Stites
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PostPosted: Tue May 15, 2007 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Diode logic circuits don't operate the same way a mixer or summing circuit does in that the input voltages are not actually summed together. A two input OR gate, for example, with a 10V signal at each input will still only put out 10V (actually it would be closer to 9.3V allowing for the 0.7V drop across the diodes).


Right. I was assuming FunkyFarm was after mixing the signals. This is a fairly standard method of mixing gates and triggers. With those types of signals, the aim is not to sum the voltages together, but rather to sum the signals together (whether one or more gates or triggers are present). The diode drop is usually insignificant in this case; it depends on the sensitivity of the device being fed from the mix. Generally, at those levels, things are rather forgiving. In the case of the Klee gate bus, the signal levels were kept consistent using the CMOS logic after the mixing. If the diode drop is a concern, one can use a 'perfect diode' solution, or what I did with the Klee gate bus.

Unless I miss the jist of FunkyFarm's question - (IE, he's wanting to mix voltage levels). In that case, yes, one would use resistors. In the case of 10V gates, there should be signal reduction, because you won't be able to mix two signals without running out of headroom.

Funkyfarm: Like Adam-V says, If you mix two 10V signals together through diodes, you'll get the 10V out, minus the diode drop.

Edit: Fonik's idea for the Schottky's is pretty good, too - at 5V levels, the diode drop will have more significance.


Cheers,
Scott
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Adam-V



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PostPosted: Tue May 15, 2007 3:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:

you could alleviate this effect using schottky (BAT38) or gemanium diodes, i guess (about 0.3V voltage drop)? could be important if you use lower gate levels...


Not a bad idea. I might knock one up over the weekend. Perhaps with an op-amp buffer on the output for good measure.

Cheers,
Adam-V
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Adam-V



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PostPosted: Wed May 16, 2007 3:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Another alternative is to use ideal diodes on the inputs like Ken Stone used on his analogue logic circuit

EDIT: or there is his Boolean Logic Circuit

Cheers,
Adam-V

Last edited by Adam-V on Wed May 16, 2007 3:38 am; edited 1 time in total
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fonik



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PostPosted: Wed May 16, 2007 3:27 am    Post subject: Re: Mixing GATES and TRIGS
Subject description: of a step sequencer.
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funkyfarm wrote:
What would be the simplest and best way to "mix" gate signals ?

so this might be two different ways to go:
simple - just diodes (passive module, using the GND from the patchcords)
best - ideal diodes (active module)

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Scott Stites
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PostPosted: Wed May 16, 2007 8:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, ideal diode (dunno why, I always call them "perfect" diodes Embarassed ). I use a modified version of Ken's Analogic for the peak/trough function in my mixer. IIRC, Ken once told me the original Serge Peak/Trough was originally created for mixing logic signals.

Cheers,
Scott
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Fri May 18, 2007 10:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
IIRC, Ken once told me the original Serge Peak/Trough was originally created for mixing logic signals.


for sure this is another scoop !

I will try to feed CGS-ANALOGIC module with gates to see if it's still happy...
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funkyfarm



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PostPosted: Mon May 21, 2007 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott Stites wrote:
IIRC, Ken once told me the original Serge Peak/Trough was originally created for mixing logic signals.


Bingo ! OR output do that very well !

ken stone's ANALOGIC module has three inputs ! just what is needed !

(if more than three step trigger are used, usually route them internally - step sequencer)
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Adam-V



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PostPosted: Mon May 21, 2007 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds like you're sorted then.

FWIW, I built a passive OR gate last night and it works brilliantly. It functions as either dual 3 input gates or single 6 input gate depending on whether there is a plug present in the 1st output socket.

I'll post the circuit and a picture tonight if anybody is interested.

Cheers,
Adam-V
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funkyfarm



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PostPosted: Fri Jul 06, 2007 11:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Yep !

Everybody is interested in passive OR gate ! Very Happy
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Adam-V



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PostPosted: Mon Jul 09, 2007 7:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here you go...


TriggerMixerSchem.gif
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2x3 Input/1x6 Input Passive OR Gate (Trigger Mixer)
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TriggerMixerSchem.gif



Last edited by Adam-V on Tue Aug 21, 2007 3:50 pm; edited 1 time in total
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funkyfarm



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PostPosted: Mon Jul 09, 2007 8:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool
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doctorvague



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PostPosted: Tue Jul 10, 2007 10:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Adam!
I'm going to build it just like yours.

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Fernando



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PostPosted: Thu Jul 12, 2007 5:32 am    Post subject: Reply with quote  Mark this post and the followings unread

IIRC, the schematic for Serge's Peak&Through is/was on the net for ages...
(see the link some messages below, thanks RF)

Anyhow, as usual, Ken did it =:)

http://www.cgs.synth.net/modules/cgs54_xor.html

Last edited by Fernando on Fri Jul 13, 2007 6:47 am; edited 1 time in total
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Funky40



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PostPosted: Thu Jul 12, 2007 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

I built my first one without the R1 to Ground. It's without any powerconnection.
It seems to work fine


My second one with Bat48 diodes is not working.
On this Module the Jacks are connencted to ground.
Seems that i have to solder in the Resistor.


Is there any importance to have the Groundconnection and R1 ?
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Adam-V



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PostPosted: Thu Jul 12, 2007 3:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

R1 is a pull down resistor which ensures that, when no voltage is presented at any of the inputs, the output is held low. This avoids the possibility of a "floating" input whatever all inputs are low.

Cheers,
Adam-V
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Adam-V



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PostPosted: Fri Jul 13, 2007 1:32 am    Post subject: Reply with quote  Mark this post and the followings unread

I finally found a few spare minutes at home to take a photo of my finished OR Gate / Trigger Mixer so here it is.


Trigger-Mixer-Photo.jpg
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And here's one I prepared earlier
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Trigger-Mixer-Photo.jpg



Last edited by Adam-V on Tue Aug 21, 2007 2:52 am; edited 1 time in total
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Funky40



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PostPosted: Fri Jul 13, 2007 3:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Ahh, you have the Resistor to Ground, but no Ground connection to the PSU............
I really don't understand this Things.
Good to see the Picture, thanks alot.
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funkyfarm



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PostPosted: Fri Jul 13, 2007 4:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Ahh, you have the Resistor to Ground,



http://electro-music.com/forum/topic-18237.html


Quote:
but no Ground connection to the PSU


ground connection is made by patch chord (with another module itself connected to the main psu) ?

No banana.
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RF



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PostPosted: Fri Jul 13, 2007 6:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Passive is nice - but the Serge Peak and Trough really added some nice options to my synth. For the minimal effort involved it has to be one of the more "bang for the buck" modules I've added.

The schematic is available many places, including this one from Ken Stone's site.

http://www.cgs.synth.net/synth/serge/pic/schem_serge_r3.gif

It's awefully simple.... and makes up for lossy diodes with a couple transistors....

Bruce
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