SPIFF! finally here, for your tremolo pleasure

[duck_arse]

I was too daunted to seach for "vibe", so I'm threading anyway ....

many years ago, someone said "spiff up your ea tremolo". and now I have, and you can. and there is no need to stop at trems, the circuit shown should work on anything using a single transistor phase shift oscillator. you know the ones. it might even work on Rick's two transistor mod from the vibe-caster, I haven't gotten that far yet.



this is my first working version of  the circuit. it has some bugs, especially in the rectifier and sensitivity/retrigger department, and someone with theory will need to pick out all the excess components, but it's a start. all suggestions and improvements welcome.

so, what does this spiff do? I hear you scream. well, you set your theshold and give a wang, the rate led lights solid, the trem stops until your thresh is reached, and then the trem starts wobbling up to depth. spiff. the osc starts gradual, w/ no clicks or planks, and dies just as gracefully on the next pick attack, leaving you with your full volume. just like RG said it would. the trem shown has a jfet input buffer, needed to isolate the clean from the tremmed signal.

so there it is, it'll take you 15 minutes on the breadboard, you can add it to your phaser or harmonic trem or dual osc/panning trem etc, etc, etc. please, let me know how it goes.

[mth5044]

Looks like a PacMan map  It's very hard to read (very crowded!), but I love the idea. Can't wait to give it a try, thank you!

[midwayfair]

Looks pretty solid, and of course I can vouch for the concept.

What's going on between R24 and R28, after the rectifier? And the threshold control isn't something I've seen before, what's the benefit of using it that way instead of simply a voltage divider after the rectifier?

Also, you probably want some way to control the decay, even if it's just a trimpot.

[duck_arse]

all the junk after the rectifier is me and my big hammer trying to smooth the ripple, I'm hopeless with rectifying/enveloping. the 324 has huge spikes in its output at D2//R24, dunno if they can be got rid of.

R28 and R29 show how much I have to learn about hysteresis. I can only get too much, or not enuff. and I seemed to be getting better trigger with the voltage ref as shown, and it biases elsewhere into the bargain.

still need a load of work, but it does work.

[midwayfair]

all the junk after the rectifier is me and my big hammer trying to smooth the ripple, I'm hopeless with rectifying/enveloping. the 324 has huge spikes in its output at D2//R24, dunno if they can be got rid of.

R28 and R29 show how much I have to learn about hysteresis. I can only get too much, or not enuff. and I seemed to be getting better trigger with the voltage ref as shown, and it biases elsewhere into the bargain.

still need a load of work, but it does work.

I think part of the problem with trying to control ripple is that you aren't really going to get the smoothest transition from "LFO working" to "LFO not working" to "LFO working again" regardless of what happens. The time it takes for the LFO to turn back on is going to depend on the rate and depth as well as the envelope action. To be honest, I've been revisiting the Blue Wabler to implement a simpler rectifier with the intention of not giving a crap about ripple because the LFO matters far more than the envelope smoothness, and the chaos is sort of the point.

However, I do have some suggestions. One thing you might try is squaring off the envelope wave a little bit so that the transients matter less. Your envelope is isolated after that first op amp, so I think you can get away with a pair of clipping diodes. Though you might also be slamming the wave already with the amount of gain present at the end.

Another option: Madbean worked up a version with an op amp LFO instead of a PSO. This sort of oscillator has a much faster recovery. This is really the FIRST change I'd make if I was really concerned about getting the envelope as smooth as possible ... no sense fighting the vagaries of the LFO at the same time as you fight the envelope! If you want a sine wave, use the LFO from the tri-vibe. You're already at a pretty high parts count here for the overall implementation, so I don't know if you have any concerns about circuit complexity and size and that's a really great LFO.

Also, Mark Hammer posted a rectifier/envelope circuit recently with a fast recovery and low ripple. He sez it's the best, and I'd take Mark's word on these things. It was comparable in parts count, so I'd go check that out. I don't have the link at the moment, unfortunately.

[duck_arse]

midway, thanks for the reply.

I recently saw, probably even saved somewhere, the hammer rectifier recommendation. I'll have another look at what I've got.

simplifing. long years ago, I added a vco to a slow gear, and spiffed that as well. only, the oscillator would choke the signal before it started tremming. and that circuit used a single darlington and diode for the rectifier section. I started w/ the 324 because I'd been stuffing wit ground referenced rectifiers, and the other bits I needed where already in there.

I'll give the clippers a go. chuck out some junk. as for the pso, well, it is an ea trem, after all.

[duck_arse]

the harry bissell envelope follower. has it fallen of the face of the earth? I can find nothing but 404's and unsafe site warnings, and the morphlag circuit. is that what I'm looking for, or can someone, anyone, provide a working link?

[duck_arse]

orlright, here is the new improved reduced but expanded spiff, v0.2



I took midway's advice while totally ignoring him, and reduced the junk. now 6 resistors and 1/2 an IC less, but 2 extra caps. somehow. anyway, the amp feeding the rectifier and the smoother section is/are different, and there is now a decay pot to fiddle with. from what I can see, the enveloping problem stems from the gaining opamp outputting a great compressed squarewave, which takes forever to decay to a point that the following rectifier actually sees any change at its input. not to mention the ripple problem.

so that's why we have a lowish-gain gainer section with the sens pot at its input. also why we have a so low ref voltage at the comparator (-) input. with the comparator values shown, and  R25//R26//C21, the mistriggers that actually mess the tremm are greatly minimised, if not entirely eliminated.

there was going to be more open space in the diagram for mth5, but it disappeared in the shifting and pushing. that's it, feedback encouraged.