a rate enveloped viber/phaser thing

[duck_arse]

someone ("three vibes" Lyman?) said we needed another magnavibe variant, so here is one with enveloped rate. it will sweep the rate up, down, or not at all, switch selectable, and also has a sweep range pot and a three range lfo, to compensate for the shorter than normal rate pot.

the audio section is based on a 2 stage magnavibe, as modded in a recent thread. it was intended for antiphase phase-sweep leds, and a PSO lfo, but one was advised against, the other was more problems than solutions (but did work, very nicely, within its limitations. and is still available for the curious).

click for bigger

for the BW version: here

for the BW version: here


[if the images have gone off the rails, it's because imgur has "gone script". another one down.]

Mark Hammer's decay rate pot also features, and works quite nicely. there is a gain preset pot shown, but I've been using a fixed 1k, works well enuff with the values shown. all of which can be tweeked, as/when/if necessary. the IC1A buffer-with-gain proved a useful sweeping addition. the sweep madness resistor was "on the bench", harnessed the madness somewhat, and went very nicely with the NSL32 sweeper, which was the only real vactrol (hence, lightproof) to hand. I didn't see any need to mess with those parts, they worked right, frist time. parts of the envelope are left from earlier failed attempts, so may appear a little odd.

the led driving section is fiddled a little, with an LM358 current-sinking the vibeing leds to allow for more usable drive-voltage swing. a rate led is included, just use a superbrite and a big resistor. the lfo is a shark's tooth single opamp type, with some resistor values chosen for rate and swing.

the sweep range pot replaces the usual stop resistor, and is meant to provide a wider sweep at higher speeds, and to lessen the swept resistance at lowest pot settings. a three position osc range allows extra slow phaser speeds, and ring-mod giddyups on the high range. it will run both Lyman fast and Lyman slow.

there is a sound file of this circuit available, but you'd be better waiting for someone else to do a less painful demo. the circuit values are semi-firmed, but the IC numberings may vary as I struggle with the perf layout.

many thanks to Kipper4 for all his help and suggestions, Ben for naming the caps and anotherjim for trying to sort me on opamps. comments and suggestions are welcomed.

[Kipper4]

No thanks needed. It was all your own hard work.
I'll breadboard it soon.

[moid]

I'm not going to pretend I understand this, but I do have a query about one of the items you mentioned on the schematics themselves - the part about not mixing the two grounds together. Does this means that both circuits are in the same enclosure but they do not share the same ground - so the first schematic will connect all it's grounds to say the ground on the DC jack, but if so, where does the second circuit connect its ground to? Or do I have the wrong end of the stick and my hand is now sticky and rather smelly? Can you have two grounds to a circuit? If that's possible it gives me an idea about a circuit I built once that has a trimmer between the circuit and the DC jack ground which acts as a weird tremolo until you plug any other pedal into the same daisy chain power supply upon which the stutter effect sadly vanishes... errmm sorry for derailing this thread!

[duck_arse]

you call that a derail?

what I should have put is "use star ground, don't mix these with those", words to that effect. if I had my layout done, I'd be able to show how, but you basically want all the audio section groans and all the env/osc/opamp/clicky grinds coming together at one point, with the (-) DC supply wire at the centre. that's best case, least chance of osc tikking. (the last layout I showed in the 'other' magnavibe thread uses 2 colours green to illustrate.)

you can wipe that hand, now.

[Kipper4]

Very nice response from the envelope on the breadboard. nice and smooth.

[Kipper4]

[duck_arse]

well, now the circuit has been confimed and demo-ed, I should get this layout all numbered and uploaded, huh.

it's all on, but it sure ain't pretty.

[duck_arse]

and so, only for the brave (or those looking for the train timetable), here is the address of the buckett, which has a perf layout and trace seperation, and the updated to match circuit diagrams.

http://imgur.com/a/HW6Qe

if anyone ever tries and build it, let me know.

[balkanizeyou]

verified!




And it really does work well. The envelope is sensitive and doesn't get stuck on extreme values, the phaser/vibe sound smooth as silk. Great job!

[duck_arse]

built? fantastic, thanks niko. details on your vactrols, for the punters? did the 'layout' pose any problems? what values did you put for the oscillator switched caps (I was just guessing those values)?

[balkanizeyou]

my vactrols are diy ones with red LEDs and LDRs swinging just under 1k Ohm in full light (I thing I used a different LDR for every vactrol, can't give you more details at the moment because all of them look the same to me). The layout was a bit tight at times, but other than the problem with squeezing one LED and electro cap in one tight place, I had no real trouble with this one. I used 470nF//1uF//3.3uF for the rate caps (the first one is real slow which is cool, the second setting gives most usable setting, and the third one is fast to super-fast).

Everyone should try this, because the effect is super-cool. If you Stephen cannot or do not want to do the PCB layout for this one, maybe you could post the perfboard tracks in black and white - it could be used as a poor man's PCB layout for perf haters like me.

[duck_arse]

If you Stephen cannot or do not want to do the PCB layout for this one, maybe you could post the perfboard tracks in black and white - it could be used as a poor man's PCB layout for perf haters like me.

done. someone needs to check the updated/replaced bukket files, V21.1 with a few small moves.

http://imgur.com/a/HW6Qe