Excellent Trigger Circuitry for Guitar

[liquids]

I've been using the EHX microsynth circuitry as my 'trigger' circuit for a while now.  It works quite well when tweaked for the task.  I've also arranged it to meet my needs without too much trouble - such as, getting an aditional trigger that only swings from 0V toward the V+ rail rather than close to the V- rail to the V+ rail, etc.  

And I personally don't find it overly complex.

As for results - I find it responsive to single notes, easy to re-trigger, and again, when tweaked for filtering and gain according to the guitar/guitarist using it, even chords can trigger well without much of any retriggering.

I've also been shown how to have the trigger pulse yield a variable pulse length (not a gate, don't be confused).  Nice, and useful.

Okay, at the same time, I am curious if anyone would recommend another circuit that is high quality and high performance!  Why not?  Maybe someone designed one that another person would say is equally good, or an even better one!  I'd want to know.  

[liquids]

the crickets chip...

Anyone have any opinions about working with the CD4098/CD4528 as a chip for a re-triggerable trigger pulse upon note attacks?   Just stumbled upon it...not sure if I have a handful or ZERO in my parts bin...but looks like it could be utilized for re-triggering, if fed a good signal? Or does it have hang ups not worth it when it comes down to it for various reasons, so as to suggest Id be better sticking with something like the EHX microsynth approach?   I'll probably use the microsynth front end since it has the critical gain and recitification and possibly more...but I'd possibly give this is a shot with one on hand (or one on order) with anyone experienced suggesting it's worth a try rather than not?    Or just be a guinea pig...

[Cliff Schecht]

If you are talking about the 4538 retriggerable monostable multivibrator chip then yes, this is a bad ass part. I used one in the sample and hold I designed for PAiA and never really had problems getting them to work consistently well. I also won an IEEE student design competition a few years ago (they give you specs on the spot and you have 4 hours to make it work) where I had to use a whistle to trigger an LED (blown once is on, again is off, and repeat). My previous experience with the 4538 is surely what won me this competition, I was the only one out of over 10 groups to get the circuit to work as specified!

[liquids]

Cliff - thanks.  I'll have to look into that.   I saw the 4528/4098 in the CMOS cookbook.  A 'find' search in a digital copy I have of that book yielded nothing for 4538 so it must not have been around at the time the edition of whatever digital copy I have...I have a hardcopy too. Of course, the 4538 does have a datasheet!  Very interesting possibilities.

In the meantime I looked at the core circuit for the Korg MS-20 ESP which has a signal to trigger...it becomes an ADSR of course...but isolated the trigger pulse section, which is mostly diodes and a 4069 stages....in LTspice, I drove it with a simulated guitar signal (strong fundamental that fades quicker than the quieter but simultanous 'octave up/2nd harmonic plus the 3rd harmonic/octave), which hence has some attack and decay characteristics like a mono guitar note.  The standard amplification/rectifier/filter preceded what I see in the MS-20 section (but uses a very LOW LPF very close towhat you see as the second LPF in the EHX micosynth), and it seemed to work....in LTspice, at least.     has a means of 'stretching' the length of the trigger pulse, which is one thing I was doing via other means previously in the VCA circuitrys chain, driven by a trigger...so, promising, but maybe outdated?  Or improvable (not that I'd know how), or inferior to using a 4538 properly - can't say.  But thanks for the lead.