EnvoTrem a work in progress

[Kipper4]

This is a work in progress. It's not perfect so if you have some advice it's welcome.

Following a recent desire to make an enveloped Tremolo I came up with this.
Thanks for the help Duck

[Kipper4]

Quick demo

https://youtu.be/l8771joPDG0

[Mark Hammer]

Nice.    I'm digging the slow-down/speed-up feature.  The fast-speed-resumption would actually be a nice feature on a Magnavibe-like vibrato, given that vibrato is less audible when slow.  Instead of tremolo, a person could pick hard and essentially defeat audible vibrato until they eased up and allowed the faster audible vibrato to come in.

As I'm sure you've found out by now, when envelope is used to control modulation rate, attack and decay times are crucial to a musical transition.  I'm wondering if that 470nf C3 is a large enough value, although the video suggests it may be okay.

[midwayfair]

Nice.    I'm digging the slow-down/speed-up feature.  The fast-speed-resumption would actually be a nice feature on a Magnavibe-like vibrato, given that vibrato is less audible when slow.  Instead of tremolo, a person could pick hard and essentially defeat audible vibrato until they eased up and allowed the faster audible vibrato to come in.

Yeah, someone should totally make this exact effect :p

Kipper: you can simplify things a bit and do it cheaper using a transistor for the envelope control instead of a second LDR. You don't need to worry about the distortion that would be created in an audio path when you're just using the transistor as a variable resistor. RG Keen's version does this with the op amp envelope like you've got, which is a bit more controllable than the transistor version in the blue warbler (which works better with vibrato than tremolo).

[bluebunny]

Nice one, Rich.  Another one for my "must try it out" list.  Also for my "check out the demo when I get back home cos work blocks YouTube (eejits!)" list.   

[Kipper4]

Thanks a million guys.
@Jon. Which RG circuit are you referring to please?
I have to admit I know jack about using transistors as a  variable resistance.
I'm sure I've breadboarded a few circuits with them but I don't get how it works on the whole so if anyone has a link to a good article or an example with explanation. I'd appreciate it.
Thanks
Rich

[midwayfair]

Thanks a million guys.
@Jon. Which RG circuit are you referring to please?
I have to admit I know jack about using transistors as a  variable resistance.
I'm sure I've breadboarded a few circuits with them but I don't get how it works on the whole so if anyone has a link to a good article or an example with explanation. I'd appreciate it.
Thanks
Rich

RG's:
http://www.geofex.com/FX_images/vibmatic.pdf

Also, note that RG's will more obviously affect the DEPTH, not the speed, necessarily, because the PSO will get messed up by too large or small a resistance range on that leg. RG talks about it a little bit. I also talk about it in the Blue Warbler doc.

To expand on this, you [probably] need to limit the range of the LDR even if you keep this configuration. [EDIT for clarity: even though you don't have the issue I'm going to describe as built/demoed, it's likely you will with some other LDRs.] If its resistance is too large, it can kill the oscillation when the speed pot's resistance is too small in comparison. If it's too little resistance in comparison to the speed pot's setting, it will kill the oscillation. You have a 1K limiting it on the low resistance side, but you need something in parallel to limit it on the highest resistance to something that will work in conjunction with your speed pot's range. I think I also talk about this in the PSO section of the Blue Warbler document, and you can also check out the Comprehensive PSO thread on this forum, which has some comments about defining the maximum possible range.

There are also other ways to go about this as far as making things easier on yourself. RG Keen's project is an addition to an existing pedal. The Blue Warbler was, frankly, originally (Ver1) my ignorance about the problems created and (Ver2) me fixing problems created by an insistence on sticking with a PSO and all-transistor design.

For instance, you could use a quad op amp for both the envelope generator and the LFO, and use the Tremulus Lune's far more stable LFO if you can live with a triangle wave (most people can). If you need a softer wave form, the Cardinal's version is incidentally more sine-like than the Lune's; or you can use the pseudosine LFO from the Tri-Vibe. If you use the tri-vibe's, you only get a single stage for the envelope generator, but there are plenty of single-op amp envelope circuits.

What you'd then be able to do with the more stable Lune LFO is that you could easily use, say, an H11F1 as a "muck it up" variable resistor (if you want to stick with optical) for either the depth or rate independently.

Let's see ... what other issues do I forsee here?

(a) Your depth pot will affect the maximum speed range, and will also result in the LED's brightness being limited when you're at low depths. While this does, to some extent, mean that you get "more bright--less bright" when it's tremolo-ing, the result is that you have a volume drop during lower depth settings. The stock Lune has the opposite problem -- which is what the volume pot on it was for to begin with. (Not to toot my own horn again, but one of the major improvements offered by using the Cardinal's LFO is that the volume is extremely consistent at various depth settings.) The other way to handle the LED is to connect it to ground instead of putting it in series, to keep the depth setting from affecting the rate. (Look at the Blue Warbler's version of the PSO -- you can use a red LED and it will be even better behaved.) This has the added benefit of making the LED not blink backwards, which I think it does in the design as drawn.

(b) If I recall correctly, when your envelope kills the oscillation as you've draw this, the LED will go dark. That means that if your envelope triggers too much your sound gets killed. I was vaguely okay with this in the original version of the Blue Warbler because I was able to make it work like a Slow Gear. But it was ... well, not what you're going for, I'm sure. (RG Keen's version doesn't have this problem because the LFO is controlling something different.) The only solution to this is to make the LED turn ON when the oscillator stops, and the only good way I was able to do that with the transistor PSO and an LED is what you can see now in the Blue Warbler. (In case it's not obvious, the end result there was also closer to how the original EA Tremolo's LFO control worked.) The Lune's LFO or some variant thereof would, again, solve most of these issues if you don't want to use the BW's because the Depth and Rate are completely separated.

I'm not discouraging experimentation, but I thought this might save you a ton of work so you're not reinventing the wheel.

Oh ... for good measure, if R7 and the decay pot are a voltage divider, you get a single control that affects the attack and decay at once AND give you a threshold control of sorts. You will have to change C3 to something bigger and use a smaller value pot, though. It would also let you shunt the envelope to ground, giving you a way to kill the envelope control completely, which you don't currently have.

[bluebunny]

Look what you've gone and done now, Rich.  Back home in the land of the unfettered internet connection, I've now seen your cool demo and I am now compelled to build this.  I'll call mine the "Tremvelope" if that's OK with you.   

[midwayfair]

I'll call mine the "Tremvelope" if that's OK with you.   

[bluebunny]

Where's the "unlike" button when you need it??   

[Kipper4]

Edited
Duck pops helped with the op amp resistor to ground tremolo set up.
I'm still hacking. I've tried some of the suggestions. Its progressing nicely although a few more bumps in the road to iron out. Differant ones to the previous ones.
I added a power filtering cap to the lfo C17 which took care of the ticking in this set up.
Note the vactrol 1 led set up.
It can be set up to ground with the anode to lfo transistor collector but i found it worked is more effective this way.
I will expand on this if needs be.
Meanwhile i'm left wondering if i should have kept this for the turkey day shoot out competition. I guess its now ruled out.
Hey ho in the spirit of sharing. Let me know if you breadboard it.
Its heading in the 1590BB direction with 5 knobies and a switch.
Enjoy

" I'll call mine the "Tremvelope" if that's OK with you.   "
Call it what you will. I just wish it was as full featured as the Pigtronix.
I suspect the pigtronix has a cmos lfo. for that "sudo" triangle wave.

Mine is a bit more quirky. it will do just tremolo on some settings. however the speed range is limited.
If you breadboard it set all knobies to midday and go from there.

[Kipper4]

[duck_arse]

turkey shoot? we got a turkey visits our backyard, doesn't need no shooting, thanks.

rich, what's that 100nF cap on Q7 C fer? it will drag your lfo signal down to ground. (then the turkey will scratch at it.)

[Cozybuilder]

Duck- How about mosquitos?

[Ben Lyman]

Duck- How about mosquitos?

I think Down Under they call them Vampire Bats

[Kipper4]

This turkey had a ticking issue hence the turkey cap. Turns out it didnt make enough differance to the tick with further use/experiments.....
So the turkey scratcher is gone.
Also I've gone back to a 5mm diffuse green led D4

[Kipper4]

So today I replaced vactrol 2B with an NSL32 in the intrest of consistency in build.
I realised that I need different clr values depending on if I'm using the inverting or non inverting input for the LED driver. IC3B. Which means a 3pdt switch.
No biggie.
It's advancing.
Next on the cards is to eliminate vactrol 1 and try replacing it with a jfet like the one in the EAN Tremolo. That is now that I'm using the resistor to ground configuration. I will probably need to loose the 100nf C16.

[duck_arse]

blast these envelopes! why can't they just do like we want? how come I haven't got the V10 drawing yet, kpr?

and what's this talk of mosquitos? I care not for them. and they are not vampire bats, but (grey headed) fruit bats - but they roost in a different tree, they too scared of the drop-turkey.

[Kipper4]

Check your inbox fruit bat.....

[Kipper4]

Quick update ver14 demo. Schematic to follow

https://youtu.be/ihQtBNF_x4k