Doepfer A-100 DIY Voltage Limiter Issues

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DespairBear
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Doepfer A-100 DIY Voltage Limiter Issues

Post by DespairBear » Thu Jul 30, 2020 5:14 am

Hello all,

Very new to DIY and electronics in general. Working on my first Eurorack module (just a basic CMOS logic module) and am trying to implement the voltage limiter as outlined at http://www.doepfer.de/DIY/a100_diy.htm under the "Voltage clamping / limiting / clipping" section

I feel like I matched the schematic but I must've done something wrong because I'm not getting any limiting on my output. I've included a picture if it's helpful. I have the + rail as +5v and the blue is GND. The lower thonk jack is the output jack. I am using the schottky Bat42 diodes as outlined in that section as well. Anybody see any immediate issues? Any information would be great, very new to all of this. Thanks in advance!

Image

socom93
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by socom93 » Thu Jul 30, 2020 5:49 am

First, you should probably connect the GNDs on your jacks, the rest of the circuit seems okay.
what signal did you put in ?

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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by DespairBear » Thu Jul 30, 2020 11:33 am

socom93 wrote:
Thu Jul 30, 2020 5:49 am
First, you should probably connect the GNDs on your jacks, the rest of the circuit seems okay.
what signal did you put in ?
I have a Levit8 mixer that will output a voltage between 0-10v when nothing is connected to it, so I was running about a 10v signal through it which didn't seem to give me any limit on the voltage when I checked the output on my Mordax DATA voltage monitor

socom93
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by socom93 » Thu Jul 30, 2020 4:38 pm

Did you connect the GNDs on the jacks ?

DespairBear
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by DespairBear » Fri Jul 31, 2020 3:28 am

Yeah, that didn't seem to solve the issue it seems... on the Thonk jacks terminal 2 goes to ground and spring contact (3) is the input voltage correct? Is terminal 1 necessary to ground? (link below is to the data sheet for the jack I'm referencing)
https://www.thonk.co.uk/wp-content/uplo ... asheet.pdf

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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by nigel » Fri Jul 31, 2020 3:42 am

1 is ground, 3 is the input / output.

socom93
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by socom93 » Fri Jul 31, 2020 3:59 am

Nigel is right, pin 2 is only connected to 3 if no jack is plugged in so in your case you can leave it unconnected

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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by DespairBear » Fri Jul 31, 2020 1:47 pm

socom93 wrote:
Fri Jul 31, 2020 3:59 am
Nigel is right, pin 2 is only connected to 3 if no jack is plugged in so in your case you can leave it unconnected
Awesome that fixed it! Thanks. Side (beginner) question, so in what circumstance would you want to connect pin 2? I'm assuming you would want to connect pin 2 to ground?

socom93
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by socom93 » Fri Jul 31, 2020 2:01 pm

It depends, sometimes yes it could be interesting to put it to ground but be careful about what is after.

Well you can do a lot of stuff with this pin2, for example i have a clock module with an internal clock that goes on pin 2, so if nothing is plug pin3 is the internal clock as well. But if you connect an external clock, it disconnect the internal clock.
The same at output jacks, i made a dual vca where if nothing is plugged at the output jack 1 then you will have the sum of channel 1 and 2 at the output jack 2.

Hope i was clear, you can really add a lot of feature to your modules with this.

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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by Rex Coil 7 » Fri Jul 31, 2020 2:09 pm

DespairBear wrote:
Fri Jul 31, 2020 1:47 pm
socom93 wrote:
Fri Jul 31, 2020 3:59 am
Nigel is right, pin 2 is only connected to 3 if no jack is plugged in so in your case you can leave it unconnected
Awesome that fixed it! Thanks. Side (beginner) question, so in what circumstance would you want to connect pin 2? I'm assuming you would want to connect pin 2 to ground?
Pin 2 is the other side of a switch ... hence "switching jack". So when there is nothing plugged in to it, a signal is sent to someplace. When you plug a cable into that jack, the signal inside that is connected to pin 2 is disconnected, and replaced with whatever is coming in through the patch cable.

So let's say you had a sound that plays when nothing is plugged into that jack. When you plug in a cable, the connection to the sound is defeated (aka broken) and the new sound in the patch cable has replaced the "no-cable sound". The jack "switches" from a normally closed set of contacts (pin 2 connected to pin 1, inside of the jack) to a different set of contacts when a patch cable is inserted (the contacts that touch the plug when it's inserted). The plug actually pushes pin 2's contacts away from pin 1's contacts, so that pin 1 is now connected to cable Tip and NOT connected to pin 2.

No cable = signal "Internal (or normaled)".
With cable = signal "Cable".

That was a horrible description, I hope it made even a little sense.

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DespairBear
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Re: Doepfer A-100 DIY Voltage Limiter Issues

Post by DespairBear » Fri Jul 31, 2020 2:49 pm

Awesome, thanks for the information, that was extremelyyyy helpful. I tried looking for information on this but mostly got results pertaining to wiring up guitar jacks and such

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