A-162 Trigger Delay mod (was: 'monoflop to ping filter?')

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Navs
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A-162 Trigger Delay mod (was: 'monoflop to ping filter?')

Post by Navs » Sun Feb 13, 2011 5:22 am

I normally use Maths channel 1's EOA to do this, but it seems an 'expensive' use of the module i.e. just to convert a gate into a trigger to ping a filter.

Does anyone use their A-162 for this and, if so, can you tell me whether it can be set for zero delay i.e. instantaneous and how hot the output is?

Maths EOA is ca. 10V, which works well. The VCS EOC is 5V, which is a bit weak for the task.

Thanks :)
Last edited by Navs on Tue Feb 15, 2011 4:42 pm, edited 1 time in total.

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Post by Reptil » Sun Feb 13, 2011 5:48 am

Yes this works.
As for the output voltage, can't measure it right now (gnomes stole my probe cables), but the module takes a tiny bit of the input signal. No problem pinging my a-121, generates a nice sinus.
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Post by Kodama » Sun Feb 13, 2011 1:03 pm

Yes the a162's length is great for getting just the right ping from my a101-2

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Post by Klopfgeist » Sun Feb 13, 2011 3:48 pm

Yes I use the A-162 for this and it works great.

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A-162 Trigger Delay timing cap DIY help

Post by Navs » Tue Feb 15, 2011 4:39 pm

Thanks for the answers, guys :)

I picked one up today and it outputs over 10V!

Great module - it doesn't re-trigger until the gate has run its course, so it can be used for cool clocking and audio applications.

However, the downside for pinging filters is that if I move the length setting a fraction off zero, the filter double triggers i.e. the gate is too long. I get more throw with Maths and this can have a marked effect on the filter's ring.

The Doepfer DIY page lists the timing caps used, so I would like to mod mine:

http://www.doepfer.de/DIY/a100_capacitors.htm

The standard value is 10 uF. If I replace this with a 1uF, I would reduce the time by a factor of 10, which would be too much.

I couldn't seem to find any 5 uF caps in the right format - are these even made? Is there a way to halve the time, similar to running resistors in parallel? The Doepfer page seems to allude to this in regard to the A-119, but I don't understand it fully.

Thanks again!
Last edited by Navs on Wed Feb 16, 2011 4:03 am, edited 1 time in total.

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Post by DGTom » Tue Feb 15, 2011 6:37 pm

add a diode to one of your passive slews so it only slopes down, the voltage drop might mean you are abit more restricted in what will drive it, but as long as you have one of Doepfers ~10V gate outs handy you should be ok to ping filters etc.

Simple Decay generators are a fantastic utility to have around (even better paired with a comparator or 2)

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Post by flashheart » Tue Feb 15, 2011 7:03 pm

I'd expect the caps form part of a CR timing circuit, so halving the resistor values should do the trick, but this may have other unseen effects on the circuit.
What I'd like to know is how you found that page, and are there any others like it - I know the main DIY page but where are the other hidden gems?

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Re: A-162 Trigger Delay timing cap DIY help

Post by felixer » Tue Feb 15, 2011 10:25 pm

Navs wrote:Is there a way to half the time, similar to running resistors in parallel?
sure. but it works out just the other way around: putting two identical caps in par will double the value. in series is half.
maybe make a little switch? i'm sure there is some room between/under the jacks .... pm me if you need help. i've got the tools & done this before :mrgreen:
flashheart wrote:What I'd like to know is how you found that page, and are there any others like it - I know the main DIY page but where are the other hidden gems?
the timing caps page is a link just at the start of the main diy page :hihi: and dieter has always been extremly helpfull if i email about some mod .... or just ask around here 8_)
tim stinchcombe's site also has a link there. many really well based mods/ideas. he's around here too ....
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Post by Navs » Wed Feb 16, 2011 4:02 am

Cheers!

DGTom, the diode might prevent re-triggering, but wouldn't get me the needle-pulse I want. However, I think the quad slew + A-162 are going to be good mates.

Flashheart, the page was linked on the A-162 page, so no Holmes-ian research on my part! I've also had very helpful, detailed responses from Dieter to my technical inquiries.

Felixer, thanks - that's what I needed to know! I'll give it a shot bzw. mail you.

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Post by Navs » Wed Feb 16, 2011 12:49 pm

Tis done - bought and modded in under 24 hours :lol:

http://navsmodularlab.blogspot.com/2011 ... -ping.html

1 uF didn't give me much more range, so I used a 0.1 uF blocking cap!

This is better, but I wonder whether the pots might also play a role i.e. lin vs log?

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Post by felixer » Wed Feb 16, 2011 1:09 pm

congrats! sounds beautifull :tu:
fm-ing with a short puls is something i do a lot on the vco to emphasize 'plek/stick impact'. mostly with the gate out on the a142. which is a bit fiddly to set right, but it works. and the lenght changes with the release time cv 8_)
concerning pots: hard to see but looks like 'A1M'? which would mean log 1 megaohm. that seems good. anyway: replacing the pots would require some surgery .... adding a range switch is easier.
Last edited by felixer on Wed Feb 16, 2011 2:01 pm, edited 1 time in total.
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Re: A-162 Trigger Delay timing cap DIY help

Post by A Dingleberry Monstrosity » Wed Feb 16, 2011 1:27 pm

Navs wrote:However, the downside for pinging filters is that if I move the length setting a fraction off zero, the filter double triggers
I imagine you could easilly add a fine tune knob. :hmm:

...well not easily in terms of realestate

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Post by MrBiggs » Wed Feb 16, 2011 3:06 pm

I still get nooby now and then: What exactly are you "pinging?" That is, is this resonance/self-oscillation we're hearing? What's the patch? Is the trigger hitting the frequency input?
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Post by Navs » Wed Feb 16, 2011 4:23 pm

Ah, I thought that might need explaining ...

Take a filter that self-oscillates, turn the resonance up to the point where it starts, then back-off just enough to silence it.

Now apply a short trigger (Maths EOA, A-162 etc. at min settings) to the *audio* input.

This should give you a Ping! (or plock, umpfh or bong, depending on tuning).

The tuning is relevant as you might have to adjust the resonance. Higher frequencies will ring earlier. Resonance sets the length of 'decay' or dampening.

The Roland TR-808 kick, for example, is a pinged band-pass filter. Experiment with filter types (LP, BP or, if you have an MMF-1, dual peak BP :love: ) and also filter slope (12dB, 24dB).

Once you've got the basic sound, you can also apply a short envelope to the filter's CV input to 'twang' your drum. Experiment with +ve and -ve envelopes to imitate the natural pitch bend that occurs when you bang a drum.

Do you still have your M12? It won't self-oscillate, but thanks to its wet and rubbery character, also sounds great when pinged. It won't 'ring', but it will pock & plop!

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Post by MrBiggs » Wed Feb 16, 2011 4:25 pm

Thanks Navs. Yeah I still have the M12 but I've been thinking of trying out the Sem20 as a possible replacement. I also have a Z2040 which will work well here. I'll try them this weekend. I've got a uStep and uScale on the way so there shall be timed and quantized pinging...

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Post by Tim Stinchcombe » Wed Feb 16, 2011 5:02 pm

Navs wrote:This is better, but I wonder whether the pots might also play a role i.e. lin vs log?
After reading this it occurred to me some simple simulations could hopefully answer the question, and I believe the answer is 'yes'.

The A-162 circuit is pretty simple: each half of the 556 timer chip (a dual 555) is used identically, and they are cascaded, so the first controls the trigger delay, and the second the trigger length. The incoming trigger triggers the first 555 circuit: the (555) output goes high, and the timing cap then starts to charge via the 1 meg pot; when the cap gets to the threshold voltage (about two thirds supply, or around 8V), it'll turn the 555 off, and the cap discharges; the second 555 sees this falling edge, and it triggers in turn, setting its output, and this is the one output from the module. The second cap charging time determines the length of the output pulse.

Thus simulating a cap charging from 10V, through a 1 meg pot gives an indication of how long either the delay or pulse will be. I have models of the 'standard' JIS pot laws (including the little 'dead zone' at either end of the travel, of which you can see the effect in the following plots by the last two traces being very close). The following curves show a 100n cap charging for 11 settings of the pot (0, 1, 2,...10); read the times off where the curves cross the 8V line. The top set are for the 'A' log law pot, then underneath the 'B' linear law. Since the 'A' law is merely two different linear slopes, you can see two distinct sets of spacings between the curves where they cross the 8V line - the longer times have a larger gap between them. For the linear pot, the spacings are more even across the whole lot, suggesting that you may have better control of the faster times if you were to change it, because the curves are not so closely spaced:
Image

[I think (and hope!) that this makes sense, and is the correct way round for the law 'A' vs 'C' pots - in any case it will be easy to check by simply measuring either the delay or pulse width at pot settings 0, 1, 2, etc. and comparing them against these plots...]

Tim

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Post by Reptil » Wed Feb 16, 2011 7:20 pm

nice, thanks for sharing, know what to do now.
:tu:

and yes, that filter sounds good, pinged
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Post by vav » Wed Feb 16, 2011 10:26 pm

Hm...i love the sound and want to try this, but i dont really want to buy a second A162 as i do use it as is...any enterprising person wanna make an expander module for it? Maybe like a 4HP with a switch for each to change from Factory to Modded and a multiple for the rest of the panel?
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Post by felixer » Wed Feb 16, 2011 10:43 pm

Tim Stinchcombe wrote:For the linear pot, the spacings are more even across the whole lot, suggesting that you may have better control of the faster times if you were to change it
thanks tim :tu: so in navs case a 'C' antilog pot might even be better ... if you can find one ... been thinking about putting a ten-turn pot into my a142. not sure if it would physically fit :hmm:
vav wrote:any enterprising person wanna make an expander module for it?
it would take an equally enterprising customer since it would involve some soldering. get your local tech to mod it for you if you can't diy. better yet: start to learn diy :mrgreen:
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Post by vav » Wed Feb 16, 2011 10:57 pm

felixer wrote:
Tim Stinchcombe wrote:For the linear pot, the spacings are more even across the whole lot, suggesting that you may have better control of the faster times if you were to change it
thanks tim :tu: so in navs case a 'C' antilog pot might even be better ... if you can find one ... been thinking about putting a ten-turn pot into my a142. not sure if it would physically fit :hmm:
vav wrote:any enterprising person wanna make an expander module for it?
it would take an equally enterprising customer since it would involve some soldering. get your local tech to mod it for you if you can't diy. better yet: start to learn diy :mrgreen:
Oh i can do the mod, i just dont know how to make circuits myself. Replacing the caps is the easy part :P
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Post by felixer » Thu Feb 17, 2011 12:37 am

replacing the caps pretty much IS the mod. then put the original part par to the new/smaller value. with one leg going thru a switch ... or is it the metalwork that puts you off? often the most expensive part of diy is a slick looking frontpanel .... if plain alu and sharpie markings don't put you off it gets a lot easier :mrgreen:
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Post by Reptil » Thu Feb 17, 2011 3:05 am

I was thinking two small switches on the Doepfer front panel.
There's plenty of space for another (small) capacitor?
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Post by Navs » Thu Feb 17, 2011 3:40 am

Thanks for taking the time to investigate, Tim!

I was toying with the delay offset last night and, of course, now realize this needs to be modded too. The range is fine for long delays, but unsuitable for subtle timing offsets or 'swing'.

What I don't understand is how, despite reducing the length cap by a factor of 100, a setting of '10' is still close to a second long. Looking at your plots and description of the circuit, am I right in thinking that the two parameters, delay & length, are linked i.e. the one influences the other?

Another mod that might be interesting would be to implement a re-trigger option, so that it triggers on each incoming impulse, but I have no idea if this is possible.

For anyone wanting in a comparator-based solution, this might be of interest:

http://navsmodularlab.blogspot.com/2009 ... rator.html

Peter's trigger delay, and my adaptation, will follow changes in timing, where the A-162 only allows fixed delays.

Also, MrBiggs, the filter-pinging/ drums description is straight out of Florian Anwander's essential 'Synthesizer' book:

http://www.schneidersladen.de/florian-a ... ynthesizer

Packed with useful information and practical examples, but sadly only in German - I've been badgering him for years to get it translated!

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Post by Reptil » Thu Feb 17, 2011 4:45 am

yes, very good! your comparator is an excellent Idea.
I got two Ken Stone Slope detector PCBs and doepfer VCLFOs planned for this purpose. but having CV-able trigger delays in one module is much neater.

the Florian Anwander articles in KEYS magazine is what raised my interest in 1996 for the doepfer systems. very clear and inspiring to go and experiment.
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Post by Chuck E. Jesus » Thu Feb 17, 2011 7:15 am

Navs wrote: Also, MrBiggs, the filter-pinging/ drums description is straight out of Florian Anwander's essential 'Synthesizer' book:

http://www.schneidersladen.de/florian-a ... ynthesizer

Packed with useful information and practical examples, but sadly only in German - I've been badgering him for years to get it translated!
i'd buy this in a second...

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