Trigger Pulse - 555 Timer - Morph-Lag - VCA

[liquids]

The subject (Trigger Pulse - 555 Timer - Morph-Lag - VCA) is my current proposed circuit block for achieving a desired goal.

Part 1:
Trigger pulse - I am using the EHX microsynth triggering circuitry to create a near-flawlessly reliable re-triggerable pulse upon attack (chord or note!).  See my thread elsewhere about using the LM13x00s in conjunction with this triggering circuitry to duplicate the MicroSynth filter.

The trigger portion of the EHX micro-synth circuit is not complex, but it's also not simple as simple goes either.  So I also have no idea if it is elegant or clunky - could it be refined, or a pulse be generated more simply?  I don't know.  IF it can, please do tell.

The way the trigger that drives the filter works is, an op amp comparator is outputing a DC voltage near the V- rail (let's say -8v on the 'classic' microsynth configuration).

Upon the attack of a note/event, a brief pulse is generated that swing as close to to the V+ rail as the op amp comparator can do so...it's there for some length (5ms, 50ms?  My sims aren't completely clear);  then it returns low until or unless a signal large enough returns it to make another near-rail pulse.

The only major simplifications to this circuit I personally can make without issue is that I have no use of the 'audio' LPF section, which is tapped to help the sub-octave track better. Since I am not using that portion of circuitry, I can leave that portion out, and the portion of the circuit known as the 'smoothing filter' by itself is sufficient.

Otherwise, outside of small tweaks, my experiment thus far don't indicate that there is much room for simplification in there, without it affecting the near-flawless triggering it gives (when set properly).

So for one, If anyone has insight in an equally reliable, but less complex circuit that triggers a pulse, I'm all ears....

More questions/issues to follow, but it's a lot to chew on all at once  

In the end I'm hoping to utilize this plus some common circuitry (as mentioned in the title) to try and create a VCA that focus on plus 'decay,' with a variable 'sustain length time' before the decay phase sets in, and then control over how long it takes to decay to zero signal, ideally with a way to make that decay varyiable between linear or log....of course some compression/limiting/sustain of the 'raw' note or signal being VCA'd is optimal to get the full benefit of such circuitry....but I sure can use some help to accomplish this.

[liquids]

Okay...

Can anyone help me with a circuit that takes the pulse of the microsynth and makes it only positive-going, and yet remains a pulse (without a noticeable decay)   Obviously I understand rectifiers.  Everything I've simmed that sucessfully goes no lower than ground, also shows the pulse as decaying/ramping down rather than retaining the shape of a pulse.

[Jordan A.]

A little bit more insight into what you are trying to do would help, what does the pulse do?  Are you firing a 555 monostable to get an adjustable and consistent pulse length? Are we talking about the Harry Bissell morph lag schematic?  Depending on what you are up to the decaying part of the pulse may be inconsequential/over too fast to matter.  A small signal diode in series may be all that you need, or you could use a schottky diode as a clipper?

It may be more expedient to just breadboard it up, rather that simulating it, but you may be more sim savvy than I am.

cheers,

jordan

[Earthscum]

Simple solution: Schmitt Trigger? That would redefine a pulse with sharp rise and fall times needed for triggering a lot of stuff, for sure, and if it's out of phase, a second one can certainly restore the phase.

[liquids]

I have no problem offering more insight, it just seems like most of my posts attempt to be comprehensive and end up getting no attention, so I aimed to simplify, in hopes of more responses.  

A little bit more insight into what you are trying to do would help, what does the pulse do?  Are you firing a 555 monostable to get an adjustable and consistent pulse length? Are we talking about the Harry Bissell morph lag schematic?  Depending on what you are up to the decaying part of the pulse may be inconsequential/over too fast to matter.  A small signal diode in series may be all that you need, or you could use a schottky diode as a clipper?

It may be more expedient to just breadboard it up, rather that simulating it, but you may be more sim savvy than I am.

cheers,

jordan

AS in the title, I was originally tryingto get a 555 to work to take a pulse (see Microsynth 'attack detetor' section)(see MFOS subcommander) and extend it's length variably, while maintaining  retriggerability .  That is, end up with a pulse that is breif as the Microsynth's pulse, to as long as a second or two....from there, I'd send it to the Bissell Morph-Lag, yes, and then use it to drive the control pin of a VCA.

From my scope, It wasn't working as simmed when I tried the 555 method on the breadboard...so I took another means.  Which worked brilliantly from trigger to VCA...except, it was not re-triggerable.  It needed me to clearly stop playing before I could reset everything to trigger the VCA again.         The microsynth trigger itself re-triggers consistently and nicely.  Not surewhy I had an issue with what I implemented, but the 'sustain' generated from the trigger pulse was generated more or less by a capacitor with variable drain time, and then comparatored so that some of the drain time comparatored 'high' so as to extend the trigger pulse put into it.  

Part of the complexity here for me is often that I am integrating bipolar rails for op amps,  with stuff that works off just half the supply (logic) and back again and sometimes forth again....  

Simple solution: Schmitt Trigger? That would redefine a pulse with sharp rise and fall times needed for triggering a lot of stuff, for sure, and if it's out of phase, a second one can certainly restore the phase.

I have a short pulse upon attack that is rail to rail minus the op amps ability to swing...how do I schmitt trigger a pulse into a longer pulse with equally long rise/fall times?  A pulse has no 'time' information to 'trick' something like a CD40106 to stay 'high' longer than the pulse, but maybe you can explain more?  Likewise, again, I need adequate rectification so as to not feed the schmitt trigger (CD40106) a negative voltage, and ususally a true comparator drives such a stage far far far far better than an op amp used as a comparator, in my experience....

[liquids]

You know, come to think of it...if you follow the microsynth schematic...it'd probably just be easier to use a parallel, separate op amp as a comparator, but single sided, out of the 'log amp' or the op amp with 4 diodes as a comparator.  Then I'd never need to worry about rectification, as the circuit that follows it doesn't want to see a positive voltage....however...my simulations show I should be getting re-triggering, however I was not.  Maybe I need to look  back and make sure I have everything in the triggering circuit as it should be.