tool to amplify gate signals

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o-ton
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tool to amplify gate signals

Post by o-ton » Sun Dec 17, 2017 6:00 am

Hi, i have a Roland System 101 i want to trigger with a cv.ocd midi/cv interface , which supplies 5V Gate output level.

I tried to trigger the ADSR with the cv.ocd Interface but it wont work properly. I tested the ADSR with a 9V Battery with the same result. Than i took 2 9V (18V) batteries and it worked.
I was told that the ADSR EG of the 101 needs +14V gate voltage to work and now i am looking for a solution for that problem.

Are there any tools in the Eurorack-format which are able to amplify a gate signal to the level i need?

thank you!

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Post by starthief » Sun Dec 17, 2017 8:33 am

Anything in Eurorack is going to max out at 12V, so no.

I use a Gozinta to boost my CV.OCD gates/triggers enough so Mini Slew will retrigger during the fall stage, but that's about 7.6V.

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Post by o-ton » Sun Dec 17, 2017 9:52 am

starthief wrote:Anything in Eurorack is going to max out at 12V, so no.

I use a Gozinta to boost my CV.OCD gates/triggers enough so Mini Slew will retrigger during the fall stage, but that's about 7.6V.
thanks for your reply!

damn, i was hoping to find a tool i the eurorack departement in order to start right away with an eurorack too, whilst my problem with the 101 is solved ;) I overlooked the max of 12V.

alright, so the only solution is a diy solution.

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Graham Hinton
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Re: tool to amplify gate signals

Post by Graham Hinton » Sun Dec 17, 2017 11:14 am

o-ton wrote:I was told that the ADSR EG of the 101 needs +14V gate voltage to work and now i am looking for a solution for that problem.
Amplification is the wrong term to use for logic signals (gates, triggers, clocks) what you need is a level translator, which can be made with a few transistors.
The +14V gate is a nominal voltage because the 101 power is +/-14V, what you really need to know is the trigger threshold voltage and its tolerance. If that is above +12V it can't be done in Euro unless you want a battery in a module (which is probably not a good idea). You may find that your 101 will trigger below +12V, but that doesn't mean they all do. Roland never gave a spec and the triggering of the EG is a bit, er, non-conventional. I suggest that you experiment to find the threshold and come back with that information.

Looking at the schematic, the peak of the ADSR (+6V) is determined by a chain of diodes below +14V and the Attack is ended by a thyristor triggering. If the Trigger voltage is too low you should get an Attack to about +5V, but it won't advance to Decay. Is that what happens?

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Re: tool to amplify gate signals

Post by o-ton » Sun Dec 17, 2017 2:04 pm

Graham Hinton wrote:
o-ton wrote:I was told that the ADSR EG of the 101 needs +14V gate voltage to work and now i am looking for a solution for that problem.
Amplification is the wrong term to use for logic signals (gates, triggers, clocks) what you need is a level translator, which can be made with a few transistors.
The +14V gate is a nominal voltage because the 101 power is +/-14V, what you really need to know is the trigger threshold voltage and its tolerance. If that is above +12V it can't be done in Euro unless you want a battery in a module (which is probably not a good idea). You may find that your 101 will trigger below +12V, but that doesn't mean they all do. Roland never gave a spec and the triggering of the EG is a bit, er, non-conventional. I suggest that you experiment to find the threshold and come back with that information.
thanks for the enlightenment! unfortunately i don´t have any electrical engineering skills to test that in depth. My test with the battery was a suggestion from someone else. I actually had to look up the internet on how to pair the 2 batteries to get 18V.
Graham Hinton wrote: Looking at the schematic, the peak of the ADSR (+6V) is determined by a chain of diodes below +14V and the Attack is ended by a thyristor triggering. If the Trigger voltage is too low you should get an Attack to about +5V, but it won't advance to Decay. Is that what happens?
You are right. That is what happens when i trigger it with +5V from the cv.ocd interface.

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Re: tool to amplify gate signals

Post by Graham Hinton » Sun Dec 17, 2017 2:24 pm

o-ton wrote: You are right. That is what happens when i trigger it with +5V from the cv.ocd interface.
In that case it would probably work from a +12V trigger if you remove 2 or 3 diodes from the chain that drops the voltage. There are three, D306, D307 and D308, in series. Try clipping a wire across them--or get someone who knows more about electronics to. Converting a 5V gate/trigger to a 12V gate/trigger can be done within Eurorack.

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Re: tool to amplify gate signals

Post by o-ton » Sun Dec 17, 2017 3:23 pm

Graham Hinton wrote:
o-ton wrote: You are right. That is what happens when i trigger it with +5V from the cv.ocd interface.
In that case it would probably work from a +12V trigger if you remove 2 or 3 diodes from the chain that drops the voltage. There are three, D306, D307 and D308, in series. Try clipping a wire across them--or get someone who knows more about electronics to.
I´d like to have some kind of an external module instead of changing something within the synthesizer. I´d like to keep my cv.ocd and go from there in the module onward to the synth.

I am not able to read the diagrams - Is it possible to measure the needed voltage? If so I am going to look for someone who can do that and if possible build me a box/module for a matching level translation.

The Synth has other patchpoints too. I assume all of them have different voltages to work correctly. It would be great to use them as well in the future. Even better would be a box where i could put in other triggers as well, e.g. voltages from a eurorack system (I hopefully have in the near future) and be able to control everything the synth has to offer, next to the adsr. However, I am really really happy once I can trigger the adsr. That´s the main goal for now.

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Post by jsleeio » Sun Dec 17, 2017 4:51 pm

http://www.doepfer.de/a1833.htm

these are cheap and will amplify your triggers/gates as far as they can go within Eurorack

(also a very useful module in other contexts!)

however as Graham hints that may not be enough
Zap him again! ZAP THE SONOFABITCH AGAIN!

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Post by o-ton » Sun Dec 17, 2017 5:38 pm

indigoid wrote:http://www.doepfer.de/a1833.htm

these are cheap and will amplify your triggers/gates as far as they can go within Eurorack

(also a very useful module in other contexts!)

however as Graham hints that may not be enough
thank you for the tip! that would be really nice if the synths adsr works with +12V. I´d buy this module instantly.

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Post by williamcarthief » Sun Dec 17, 2017 5:57 pm

At one point I thought I had a kind of similar problem. I couldn't get the gates from my hexinverter midi2cv to trigger some envelopes consistently but it turned out I just was sending gates too fast and those specific envelopes weren't capable of receiving another gate until they completed their cycle. Before I figured that out though I thought it was a gate level issue and I was looking for a solution. I found Ladik's A-520 4 channel preamp which amplifies at 12db or 20db depending on jumper settings. He thought it would work but would need to be modified to be dc instead of ac coupled which he did for me at no charge. It's a pretty inexpensive module.

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Re: tool to amplify gate signals

Post by Graham Hinton » Mon Dec 18, 2017 1:39 pm

o-ton wrote: I´d like to have some kind of an external module instead of changing something within the synthesizer. I´d like to keep my cv.ocd and go from there in the module onward to the synth.
To convert a 5V gate to Roland's +14V level is trivial, it can be done with a couple of transistors. Powering those transistors is the problem: is it worth building another PSU for a tiny circuit or can the 101's be used? As the 101 is the fly in the ointment I suggest having a small circuit board fitted inside so that it can be triggered from any voltage above 2V. Then anything can trigger it.
The Synth has other patchpoints too. I assume all of them have different voltages to work correctly.
Not really, Pitch CVs and signals are the same and the 6V envelopes just need a little gain adjustment. The +14V trigger outputs could damage some Eurorack trigger inputs.

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Re: tool to amplify gate signals

Post by o-ton » Tue Dec 19, 2017 5:54 am

Graham Hinton wrote: To convert a 5V gate to Roland's +14V level is trivial, it can be done with a couple of transistors. Powering those transistors is the problem: is it worth building another PSU for a tiny circuit or can the 101's be used? As the 101 is the fly in the ointment I suggest having a small circuit board fitted inside so that it can be triggered from any voltage above 2V. Then anything can trigger it.
it sounds really like the best solution. no extra box and any trigger signal above the 2v level can trigger it. sounds great!

Not really, Pitch CVs and signals are the same and the 6V envelopes just need a little gain adjustment. The +14V trigger outputs could damage some Eurorack trigger inputs.
Alright, so I should be able to use any patchpoint like fcv in offered from the synth. cv pitch works with my +5V midi/cv Interface.
I was only looking at triggering the synth not the other way round. so the +14V output i won´t use anyway.
thank you for your help!
I am thinking about who can build such a circuit board and install it near my area.

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Post by kluber » Sat Dec 30, 2017 12:44 pm

I own myself a 101 (also the 102) and share the same frustration about this.

I remember there was a guy talking about a small circuit to convert the gate signal in this thread:

https://www.muffwiggler.com/forum/viewt ... sc&start=0

Unfortunately pictures are now gone from the thread (although you could PM Lilakmonoke) or juste visit this french page:
https://fr.audiofanzine.com/synthe-anal ... ible-7061/

I haven't built this circuit yet but will do soon probably.

Otherwise I'm wondering how to modify the 102's sample and hold circuit to work with external gate.
According to the schematics, I should disconnect the clock (which trig the sample and hold) at the diode D201 (install a switch there) in the VCO board and hook up an external clock but it should be a -14V clock signal which is inverted. What do you guys think about it? Could this work or is it pure fantasy? :hmm:

Also thanks to a friend I have build a circuit that provides Square/PWM SUB -1/-2 octave (by the way this is a non destructive mod)
ImageImage

PS: You should solder a switch between the -1 octave and the -2 octave outputs then connect the common pin to the external input socket in the way than when a jack is inserted then the sub circuit if disconnected

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Post by Graham Hinton » Sat Dec 30, 2017 3:58 pm

kluber wrote:Also thanks to a friend I have build a circuit that provides Square/PWM SUB -1/-2 octave
This circuit has the same problem as the Roland circuit: it is trying to implement a digital logic function with analogue circuitry. The mistake is buffering the input with a transistor voltage follower, which has a diode voltage drop, and then dropping its output with another diode. This produces a signal that is dependent on the input voltage and is over a volt less and using that to drive a digital input. That is why it doesn't work with lower voltage gates and it is a bad way to do it.

Here is how simple it is to do properly:

Image

Both transistors are used as switches, not amplifiers. The first transistor turns on at any input voltage above about 1V, this then turns on the second transistor which pulls the output up to +ve (+14V taken from the Roland). It assumes that the input is a Gate and has a fairly fast rise/fall time and is not an analogue signal like a LFO triangle. If you want to use slow rise/fall signals you need a Schmitt trigger.

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Post by kluber » Sun Dec 31, 2017 8:06 pm

Hey Graham, thanks for your design.

Actually I've "built" but haven't' make it work.
Since it was sunday I used what I had around me for the 2N3906 and found the 2SA733 instead (seemed to be alright except the pinout).

I inserted the small circuit just before the junction 55 (see picture beneath) as it was suggested for the circuit I talked on my previous post (the one in french). Meaning the Gate Input socket is connected to the small circuit's Input and the Input Trigger is connected to the Pad 55 (or R329)

Image

All I got was a continuous sustain ATTACK, DECAY or RELEASE were no more functional.

I certainly did something wrong but what could it be? Here is the breadboard version of your circuit I've used. Would you mind checking if there is some errors please?

OH and by the way Happy New Year to you all! :party: :banana: :bananaguitar: :party:

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Post by kluber » Sun Dec 31, 2017 8:06 pm

Double post

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Post by boubi » Mon Jan 01, 2018 7:06 am

Does the 101 have a preamp module? If you are, like me, reluctant to DIY (lack of skill), that's how I solved the problem for my ARP 2600 which too requires hot gates.
ARP 2600, ARP Sequencer, EMS Synthi E, Waldorf Microwave XT, Korg z1, microKorg

https://boubis.bandcamp.com/

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Post by Graham Hinton » Mon Jan 01, 2018 7:37 am

kluber wrote:All I got was a continuous sustain ATTACK, DECAY or RELEASE were no more functional.

I certainly did something wrong but what could it be? Here is the breadboard version of your circuit I've used. Would you mind checking if there is some errors please?
That means that the 2SA733 is not switching off. Try a resistor like 10k between its base and emitter so that it is driven by voltage rather than current.

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