Connect simple switches to eurorack synth

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burnboardburn
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Connect simple switches to eurorack synth

Post by burnboardburn » Wed Jun 10, 2020 3:55 pm

Hi,

I am about to use/connect an interface consisting of many (single throw) momentary switches. These are meant to be performed live in a fast erratic way, and I expect to get a very glitchy result. Essentially it will be like connecting and disconnecting a patch cable, but very fast, a tremolo sort of.

However, I want to make sure I do not harm the synthesizer. I figure it will not be a problem, but I would appreciate some advice.

I am pondering if I should use capacitors to smooth out the switching, but the less electronic components the better.

i am very thankful for help!

Cheers.

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Re: Connect simple switches to eurorack synth

Post by Grumble » Wed Jun 10, 2020 4:26 pm

Do you want to switch control voltages or audio signals?
I’m asking this because control voltages are relatively slow and you could use capacitors and resistors to remove most if not all of the glitches.
Audio signals (which are relatively fast compared to control voltages ánd are audible) is a whole different ballgame using switches like that.
Better to use cmos switches or the like. (I have some AD7510 switches which are obsolete now...j

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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Wed Jun 10, 2020 8:29 pm

My advice would be to use VCA's with big fat caps on the VCA CV inputs. You can build all of this stuff. That way the VCA CV slew and the button denounce is combined into a single capacitor. I don't know if you want all that switch noise in your signal path. Some people do. The problem is that you need a DJ crossfader or an arcade button or touch input or keyboard or something to get fast performance switching. MN teleplexer is made for tapping on cables but the module also is disposable and the patch cables get damaged over time.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Thu Jun 11, 2020 8:04 am

Hi,

Thanks for the replies.

Here are the "switches" . In this picture they are chopping audio signals and battery powers. No electronics in between. Sounded great!
IMG_0225.JPG
IMG_0227.JPG
I will do the safety preparations, if needed, in the weekend on breadboard. On Monday I connect to the synthesizer. Unless I risk destroying it.

In case I would like to remove some glitches, how would I wire the capacitors and/or resistors for CV respectively audio?

Thanks a lot!
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Re: Connect simple switches to eurorack synth

Post by mskala » Thu Jun 11, 2020 8:59 am

It's unlikely to harm the synthesizer, but depending on what you're using the outputs for, if you don't debounce them they may produce effects you don't want. For instance, a switch used to generate a trigger signal into a sequencer or similar may register more than one trigger when it switches, because of bounce. An RC filter - basically just a resistor and capacitor - would be the easiest way to address bounce.

However, it sounds like you want to use these as switches per se - that is, to connect and disconnect signals, including audio signals. In that case I would not recommend adding capacitors to debounce them because the caps would eat your high frequencies; there's no meaningful difference between the high frequencies of the contacts bouncing and the high frequencies in your audio signals. Just go ahead and run your signals through the switches.

You mention using these instead of patching and unpatching patch cables, and that's a clue to the safety issue for the synthesizer. If it's safe to plug and unplug a patch cable, then it should be safe for the electronics to switch the connection on and off with a mechanical switch.

Something else to be aware of is safety for the human user. From your photos it looks like the human user will be directly touching metal that's connected to the signal path. In that case it's even more important than usual that the system should be safe with respect to electric shock. We occasionally get postings here from people saying things like "I get a tingle of electricity in my fingers when I touch such-and-such metal part of my synth, is that a problem?"; that is a problem, caused by unsafe power connections, and it's something to watch out for in a setup where humans are meant to be directly touching metal that's connected to the circuit. Be sure your power system is safe.

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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Thu Jun 11, 2020 11:05 am

I did this in 2012. it has momentary, latching, inverse momentary.
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Re: Connect simple switches to eurorack synth

Post by ersatzplanet » Thu Jun 11, 2020 11:24 am

I'm selling off the last of my inventory of these, MG-1 manual gate pushbutton modules. Waiting for some parts to finish off the last bit. They use SPDT micro switches in a pinball machine mechanism.
MG-1-slant-sm.jpg
Contact bounce is a real problem with almost all mechanical switches. Cutting a signal off or turning it on in any place other than a zero crossing will make a snap or pop. I would suggest buying some cheap Vactros from a surplus site and run the signals through them. The Vactros are not fast so the edges will not make the pops that a switch by itself will do. Basically you would be making your own version of the DivKid Mutes module. IIRC he was going to release the circuit drawings at one time.
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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Thu Jun 11, 2020 11:59 am

why haap over sanway or seimitsu? personal preference?
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Thu Jun 11, 2020 2:15 pm

mskala wrote:
Thu Jun 11, 2020 8:59 am
It's unlikely to harm the synthesizer, but depending on what you're using the outputs for, if you don't debounce them they may produce effects you don't want. For instance, a switch used to generate a trigger signal into a sequencer or similar may register more than one trigger when it switches, because of bounce. An RC filter - basically just a resistor and capacitor - would be the easiest way to address bounce.

However, it sounds like you want to use these as switches per se - that is, to connect and disconnect signals, including audio signals. In that case I would not recommend adding capacitors to debounce them because the caps would eat your high frequencies; there's no meaningful difference between the high frequencies of the contacts bouncing and the high frequencies in your audio signals. Just go ahead and run your signals through the switches.

You mention using these instead of patching and unpatching patch cables, and that's a clue to the safety issue for the synthesizer. If it's safe to plug and unplug a patch cable, then it should be safe for the electronics to switch the connection on and off with a mechanical switch.

Something else to be aware of is safety for the human user. From your photos it looks like the human user will be directly touching metal that's connected to the signal path. In that case it's even more important than usual that the system should be safe with respect to electric shock. We occasionally get postings here from people saying things like "I get a tingle of electricity in my fingers when I touch such-and-such metal part of my synth, is that a problem?"; that is a problem, caused by unsafe power connections, and it's something to watch out for in a setup where humans are meant to be directly touching metal that's connected to the circuit. Be sure your power system is safe.
Thanks, that makes it clear. +1 for human safety heads up. I could use gloves, but I am also quite sure that the synth and the studio is in mint condition.

I did hope and assumed that it would be no more harmful than plug in and take out a patch cable, but the difference is the speed. I use the springs to create pulses between a couple of seconds to I guess milliseconds. I was thinking that it could occur some kind of build up of.. um, something.

Anyway, yes it is like an intended bouncing. I think I will set up a few RC filters on breadboard and then I can patch through it in case I find a CV connection too bouncy.

I was also pondering if I should make the spring-switches control a relay/transistor. But it seems overly complicated or awkward in this senario.

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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Thu Jun 11, 2020 2:32 pm

EATyourGUITAR wrote:
Wed Jun 10, 2020 8:29 pm
My advice would be to use VCA's with big fat caps on the VCA CV inputs. You can build all of this stuff. That way the VCA CV slew and the button denounce is combined into a single capacitor. I don't know if you want all that switch noise in your signal path. Some people do. The problem is that you need a DJ crossfader or an arcade button or touch input or keyboard or something to get fast performance switching. MN teleplexer is made for tapping on cables but the module also is disposable and the patch cables get damaged over time.
Great, the MN teleplexer kind of proves that it is OK, assuming that there is no fancy circuits beneath.

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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Thu Jun 11, 2020 2:50 pm

burnboardburn wrote:
Thu Jun 11, 2020 2:32 pm
Great, the MN teleplexer kind of proves that it is OK, assuming that there is no fancy circuits beneath.
people reported the gold plating would wear out under normal use over time causing the module to not work as intended. there are much thicker gold plating processes available for this kind of application. the teleplexer seems to be a standard PCB that is not designed to be used in this way. or maybe they just don't expect people to use them for many hours.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Sat Jun 13, 2020 5:14 am

Additional question:

I will connect the spring-switches to a breadboard, and then make wires with a 3.5 in one end and a pin in the other end. I may make a simple breakout box too.

Will it be enough with just one patch cable with ground and the others with just the tip connected? I want to reduce soldering and connections.

Thanks!

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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Sat Jun 13, 2020 8:04 am

burnboardburn wrote:
Sat Jun 13, 2020 5:14 am
Additional question:

I will connect the spring-switches to a breadboard, and then make wires with a 3.5 in one end and a pin in the other end. I may make a simple breakout box too.

Will it be enough with just one patch cable with ground and the others with just the tip connected? I want to reduce soldering and connections.

Thanks!
yes but you may not have a good noise floor with thin unshielded flying wires plugged into a breadboard with a common ground. experiment with isolated vs grounded power to see what has less 60Hz hum in the audio output. fluorescent lights will totally bleed mains hum. this is called electro magnetic interference. if you have an isolated power supply with unbalanced (single ended) cables plugged into the house mixer which is grounded, you are still grounded and no ground loop. the problem with that would be the lack of shielding. grounding in two places in a larger venue could have a ground loop. no shielding means it will be a struggle to get it working in every venue without mains hum.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Mon Jun 15, 2020 2:41 pm

EATyourGUITAR wrote:
Sat Jun 13, 2020 8:04 am
yes but you may not have a good noise floor with thin unshielded flying wires plugged into a breadboard with a common ground. experiment with isolated vs grounded power to see what has less 60Hz hum in the audio output. fluorescent lights will totally bleed mains hum. this is called electro magnetic interference. if you have an isolated power supply with unbalanced (single ended) cables plugged into the house mixer which is grounded, you are still grounded and no ground loop. the problem with that would be the lack of shielding. grounding in two places in a larger venue could have a ground loop. no shielding means it will be a struggle to get it working in every venue without mains hum.
OK, this setup is only for a couple of sessions in a studio, so it should be fine. I actually found a solution with breakout boxes with different connections (6.3 TS, 6.3 TRS, RCA) that I convert to 3.5 mm.

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Re: Connect simple switches to eurorack synth

Post by J3RK » Mon Jun 15, 2020 3:00 pm

EATyourGUITAR wrote:
Thu Jun 11, 2020 11:59 am
why haap over sanway or seimitsu? personal preference?
I've always liked Happ/Suzo parts myself, but they're the ones I have the most experience with. They also make the smaller convex buttons that feel very nice. I've been using them for decades though for game devices, so it's really a matter of not having tried anything else.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Mon Jun 15, 2020 3:05 pm

It actually so far turned quite good, thanks for the support.

Next step would be to be able to trigger easily with CV.

It works fine with breaking audio signals, for example FM modulation. I try to avoid switching direct to output in order to sound a bit tidy.

CV works, but I have to take the voltage from a module even if I just want a static voltage. It is a bit wasteful on modules (I used an EG). So I am thinking that I could add some batteries to my breadboard with the static voltages that I need. A perhaps more safe solution than connecting a DC power supply.

What voltage would I need for a trigger signal (High)? Maybe I could use three AA batteries (4.5v). Can LOW just be open, or should it have a voltage too? 1.5v? And a 9v for simulating a static positive CV signal?

Or, is there some brief guide where I could read up upon voltages how they are used in eurorack systems?

Thanks a lot :)

This is the final setup:
DSC_0668.JPG
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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Mon Jun 15, 2020 4:40 pm

Video game controllers have a pull-up resistor at the input of the microcontroller in the game controller. The same is true for a computer keyboard. That way the switch wiring can be bus to ground on one side. Because of the pull up resistor and the limitations of the microcontroller, no one will ever get electrocuted using this method unless something else is really wrong somewhere else in the system. You definitely don't want exposed power supply terminals if you already have exposed the ground. The 10K pull-up inside an Arduino that can sink or source 20mA max at 5v or 0v. It is relatively safe.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Tue Jun 16, 2020 5:18 am

Cool, thanks.

I found these threads:


https://muffwiggler.com/forum/viewtopic.php?t=169120


https://www.muffwiggler.com/forum/view ... 7&t=96737

It seems I could use a 9v battery to trigger successfully.

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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Sat Jun 27, 2020 2:46 pm

As a conclusion, here is a little clip from the sessions with the setup. Erica synth entangled by my thingies. Thanks for the help!


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Re: Connect simple switches to eurorack synth

Post by EATyourGUITAR » Sun Jun 28, 2020 10:11 am

That's cool but maybe with all those voices it makes it less dramatic. There needs to be some easier way for the viewer to associate the visual performance with the audio sources. Blue man group is an example of that. More envelopes more vca more silence between notes. If people don't understand it and can't associate sounds with previous experience of familiar sounds then it becomes auditory stimulation but not really the big emotional connection that a music performance can make.
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Re: Connect simple switches to eurorack synth

Post by ersatzplanet » Sun Jun 28, 2020 1:43 pm

EATyourGUITAR wrote:
Thu Jun 11, 2020 11:59 am
why haap over sanway or seimitsu? personal preference?
Basically if is that most short profile switches come only in SPST and I wanted SPDT switches.
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Re: Connect simple switches to eurorack synth

Post by burnboardburn » Mon Jun 29, 2020 8:50 am

EATyourGUITAR wrote:
Sun Jun 28, 2020 10:11 am
That's cool but maybe with all those voices it makes it less dramatic. There needs to be some easier way for the viewer to associate the visual performance with the audio sources. Blue man group is an example of that. More envelopes more vca more silence between notes. If people don't understand it and can't associate sounds with previous experience of familiar sounds then it becomes auditory stimulation but not really the big emotional connection that a music performance can make.
That is some good points IMHO. This setup with such small objects are not meant to be experienced visually, they are only meant to control sounds and be performed by me. Except if I make an interactive installation of it, but then I usually make larger objects (then it is easy to understand the functions) . The video is also just a chaotic teaser live shot while experimenting the studio ( recorded by the camera mic...). One thing I really miss is dynamics, but it is difficult to make that a logic functional of these springs.

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