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about the CGS Gate to Trigger Converter...
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author about the CGS Gate to Trigger Converter...
audioCTRL
- has anyone built it? Does it work with +/- 12 volts as Ken Stone claimes?
Or even better, is there a more simple way of converting Gates to Triggers? (space is an issue...)

THANKS!
falafelbiels
well, it's a simple enough circuit as it is, but you could try it passively with just the parts before the opamp. So this would be 1 capacitor, 3 resistors and a diode.
You may need pretty hot gate signals though.
audioCTRL
falafelbiels wrote:
well, it's a simple enough circuit as it is, but you could try it passively with just the parts before the opamp. So this would be 1 capacitor, 3 resistors and a diode.
You may need pretty hot gate signals though.


Thanks Falafelbiels!
A passive circuit would be ideal.
hmmm..... I'll breadboard it.. If the output isn't hot enough to fire my ADSRs I'll add power and opamps.
diophantine
audioCTRL wrote:
- has anyone built it? Does it work with +/- 12 volts as Ken Stone claimes?

The power is only used for the op-amp power, and for the comparator threshold (via the voltage divider).

The LM358 will operate just fine with a +/- 12V supply.

With a +/- 15V supply, the comparator threshold is ~2V. (i.e. the input gate must exceed 2V to get an output.) With the same resistor values and a +/- 12V supply, the comparator threshold is ~1.6V. I suppose for most applications this should be fine. If you really want to bump it up closer to ~2V, you could replace the 15k resistor with a 20k resistor (or something in-between).

So yes, it will work fine with +/- 12V!
Monobass
audioCTRL wrote:
falafelbiels wrote:
well, it's a simple enough circuit as it is, but you could try it passively with just the parts before the opamp. So this would be 1 capacitor, 3 resistors and a diode.
You may need pretty hot gate signals though.


Thanks Falafelbiels!
A passive circuit would be ideal.
hmmm..... I'll breadboard it.. If the output isn't hot enough to fire my ADSRs I'll add power and opamps.


did you try it? how hot did your gate signals need to be? gates I want to use are +8v
J3RK
I've done this passively. I can't remember the exact circuit off the top of my head, but I think it was just a cap with a resistor to ground on either side of it. (4n7 or 10n if I remember correctly, with 47K-100K resistors maybe?) I think you can stick a diode in there too to make it work a touch better. I'll see if I can dig up what I used.

I've also done it with a potentiometer, which can be used to vary how sharp the decaying slope is after the initial spike. Not hugely useful, but you can decide how long the trigger should be this way.

I prefer an active solution myself though. I'll see what I can find when I get home.

Edit: Nevermind, I found where I originally got the passive one from: http://forums.adafruit.com/viewtopic.php?f=13&t=5060
Monobass
Just tried the passive section of the CGS one (the section in red).... giving it 8v gate in is giving me 4v trigger out... triggers all clocky/logic things in my system fine as expected, syncs my MOTM e350, only thing I can't get it to do is resync my Z3000.

Didn't want to use it to resync my Z3000 anyway... success smile

Jarno
Excellent news, still want to add trigger outs on my flopseq sequencers, actually thought about adding a transistor instead of an opamp, but completely passive will do just as well. thumbs up
Monobass
So could this circuit be modified so it produces a positive trigger on gate off rather than gate on?
elmegil
Seems like you ought to be able to invert it (classic transistor inverter) before the first stage.....
Monobass
elmegil wrote:
Seems like you ought to be able to invert it (classic transistor inverter) before the first stage.....


yeah of course d'oh! i was overthinking it!
clusterchord
Monobass wrote:
Just tried the passive section of the CGS one (the section in red).... giving it 8v gate in is giving me 4v trigger out... triggers all clocky/logic things in my system fine as expected, syncs my MOTM e350, only thing I can't get it to do is resync my Z3000.

Didn't want to use it to resync my Z3000 anyway... success smile



i have a Thomas White Dual LPG (its finished but yet to be wired). afaik this LPG like most needs a short trigger instead of gate to fire off.

i was thinking of adding two more jacks with this passive circuit in front of each LPG channel. these would be something like "strike" inputs on Makenoise Optomix. this way i could avoid sacificing an envelope generator or maths channel for triggering LPG.


would this passive circuit work i.e. is the output trigger strong enough to trigger the TW LPG ? or i need an opamp too?



thanks
elmegil
The circuit is designed to have the passive part buffered by a comparator which also brings the levels back up.

I think the only way to be sure whether just the passive part would work is to build one on protoboard or a breadboard and test it out.
Navs
clusterchord wrote:
would this passive circuit work i.e. is the output trigger strong enough to trigger the TW LPG ? or i need an opamp too?


Try it. IIRC I used it once on Ken's Drum Simulator and didn't get the expected result.

If you are going to mod your LPGs, you may as well do it properly i.e. with an opamp. Here is a gate-to-trigger circuit I used on my A-143-1 mod:



http://navsmodularlab.blogspot.de/2013/01/a-143-1-modification.html

I remember Dann from 4ms suggesting in another thread that the cap alone would suffice to HP filter a gate. The problem is you'll get double triggers, hence the diode on the output post opamp.

That said, I've found it's nice to be able to vary the length of the trigger. This makes a big difference when pinging 'normal' filters for percussive sounds. My solution was to mod an A-162:

http://navsmodularlab.blogspot.de/search?q=a-162
(various A-162 mods)

So, while it's handy having an inbuilt 'strike' trigger, an external one is better.
clusterchord
Navs wrote:
If you are going to mod your LPGs, you may as well do it properly i.e. with an opamp. Here is a gate-to-trigger circuit I used on my A-143-1 mod..

..That said, I've found it's nice to be able to vary the length of the trigger. This makes a big difference when pinging 'normal' filters for percussive sounds. My solution was to mod an A-162:

http://navsmodularlab.blogspot.de/search?q=a-162
(various A-162 mods)

So, while it's handy having an inbuilt 'strike' trigger, an external one is better.

thanks for all the info, ive read all about your three A162 mods, and agreed, i'd definitely prefer flexibility and possibly voltage control over the pulse lenght that goes into LPGs.

btw can A-162 also accept triggers on input, or just gates?


also, now i have a dillema: there's A-142 that already has CV of decay, with potentiometer, and consequently CV of output gate lenght - if i went with that option, will it also need "speeding up" caps to get it into usable range of mililseconds?

it only has a trigger input.. so, i presume if i want to use it with gates too (from keyboard etc) it would need the, previously discussed, little CGS circuit in front?

thanks
Navs
The A-162 & A-142 accept triggers and gates. The point is that they 'ignore' the gate length - they are only interested in seeing a rising edge. thumbs up

On the min/ max times of the caps, ask Dieter: hardware (ät) doepfer (döt) de. I haven't got an A-142 any more, but I remember it being pretty fast. It was the A-162 that had the - for me - unusable ranges.
clusterchord
Navs wrote:
The A-162 & A-142 accept triggers and gates. The point is that they 'ignore' the gate length - they are only interested in seeing a rising edge. thumbs up


awesome , that is exactly what i want out of them. to enter with whatever gate lenght or a trigger, and get it delayed and output with a gate that is set by controls.

about the CV control,, not clear from the blog - did you add CV for the Delay or the Lenght parameter?

delay could be fun for rhythms, but lenght is what would make LPGs "spit" differently on different notes.. think more interesting to me.


beside the CGS, i've read about various CV options on muffs, and one that has been mentioned few times, that gets linearity but avoids vactrols, is using a dual VCA like ssm2164...

what are pros/cons here .. isolation? is this what euro manufacturers use when adding CV inputs to their modules?

i was thinking of picking up a few coolaudio 2164 remakes for this, as there's quite a few things i'd like to add CV control to. like MA CVP, a162, and some other things..
Navs
I modded one section for delay and the other for length.

You could consider the H11f1:

http://navsmodularlab.blogspot.de/2013/01/a-143-1-modification.html

The SSM VCA is used for the fact that it has 1V/O VC built-in e.g. when used in the core of a VCO, VCF or VCA. I'm not sure people are using it to add CV control to an existing circuit.

There comes a point when building a custom module is the same amount of work as modding e.g. a 555 timer chip based mono-flop circuit.
drewskee
Monobass wrote:
Just tried the passive section of the CGS one (the section in red).... giving it 8v gate in is giving me 4v trigger out... triggers all clocky/logic things in my system fine as expected, syncs my MOTM e350, only thing I can't get it to do is resync my Z3000.

Didn't want to use it to resync my Z3000 anyway... success smile



Noob Question: I can tell the resistor values but the capacitor is 10n = ? and what is the diode that should be used? I have an EMS Synthi that needs a +4v Trigger and I want to create a passive Gate to Trigger converter so I can ping the Envelope with no Sustain time.

Any help appreciated!
Jaytee
4148s will work for the diode. It’s not clear exactly what your question about the caps is, but if you’re trying to figure out what kind of cap to use... Ive used film caps to build the active version before, but I’d wager that the capacitor type is not critical here.
roglok
10n = 10 Nanofarad = 0.01 Microfarad
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