Magnavibe vibrato/tremolo blend mod for rotary speaker effect

[Mark Hammer]

I used the very first one you posted in this thread, without any gain-recovery stage on the output, just straight off the second 100nf cap.  I hadn't realized until you asked that there had been such a succession of changes over the 7 pages.  Apparently the first one was good enough for me.  If the subsequent ones offer any improvement, I would imagine it to be marginal, or simply an adjustment to the quirks of the parts used.

[Ben Lyman]

cool, thanks. Glad you like it. The only change I feel is important to the first one is to wire the LEDs in series rather than parallel. This was Duck's advice and it does improve the wobble steadiness. The reason for two LEDs is not only for the option of mounting one on top as a rate indicator but it affects the other LED within the vactrol so as to make it a little more "seasick"
My first scheme with the LEDs in parallel achieves the affect but also causes an irregular wobble.

The 9k2 resistor is perfect for throwing on a switch, that's how one of my earlier boxes is set up, actually a 10k trimmer adjusted to taste.

My latest one, the one with 4 knobs as seen in the last vid, is kinda weird but I like it, because I used a 100k pot for that control. I can go from plain vibrato to some weird but very musical and useable wibble-wobbles

[Plexi]

Nice thread!

I finished on this morning, and have something to add:
I use BC548, and trying to "pushing" it with a LPB1 in the front, you get a really nice overdrive.
I'll share a video soon

[pinkjimiphoton]

when i had built one of these years ago, i ended up using one of them 10mm waterclear led's. worked great... plenty of wobble, and more volume than the smaller led's. seemed to be a little phasier too... maybe from needing more current?

maybe itt was the acid... i dunno

[ljudsystem]

Hi everybody

Great inspiring thread 

I'm breadboarding my own magna/rotary but I can only get a very subtle pitch wobble. I only have standard red leds.

You have any advice on leds? Will leds with a higher mcd give more modulation? do Ldrs react better to certain colors?

[pinkjimiphoton]

best i got was what was posted in the post just before your last post

its a funky circuit. it wobbles way more at higher speeds than lower ones. but i think brighter leds seem to work better.
been forever, i sold mine to a bud who took it on tour to europe and never came back. yet, anyway that was a couple years ago.

[deadastronaut]

You have any advice on leds? Will leds with a higher mcd give more modulation? do Ldrs react better to certain colors?

its a mix of both really imo....but make sure you have them covered with heatshrink...

no light pollution..for full effect...

[anotherjim]

Higher MCD in a LED usually means its emission is focused on a narrower beam. If it misses any of the LDR's active surface, it might be no better than an weaker, ordinary LED.

[duck_arse]

using this as reference [because it was the first I came across looking], if you fiddle the value of C4 you can, to a certain extent, compensate for led funnynesses. ifn you run the led too bright, the ldr won't swoosh from low R to high R as much.

are your standard leds diffused or waterclear or tinted? are you using a winky indicator led as well?

[oddly, just today, I've started at this circuit again.]

[Plexi]

As my experience, this design IS per se very very subtle.
It's hard to get some strong/deep vibrato or tremolo from it.

Someone says that they have good resulta with green leds.
But, I think it's more important wich LDR are you using and the mentioned light isolation

[ljudsystem]

Thanks for the advice guys.

The leds I'm using now are diffused red leds but i'm thinking of hedding down to Kjell och co (the swedish equivalent of Radio Shack) and they have leds in all colors, sizes etc. but they only sell them in bags of 100 I think otherwise i would buy one of each and experiment.

Yeah, the 10n cap really helps, the first vibe i built rolled of allot of high end.

I actually  went completely overboard with the project and split the signal via a AMZ splitter, hi-passed one and lo-passed the other and sent each signal to its own magna/tremolo to simulate the Bass/treble rotors 

[ljudsystem]

BTW

What is a "winky" led?

[thermionix]

(the swedish equivalent of Radio Shack)

If it was truely an equivalent, you wouldn't be able to find one.

What is a "winky" led?

I think he means an "effect on" indicator that blinks at LFO speed.

[Ripdivot]

I recently built a version of this circuit. I tried many different "roll your own" opto couplers. They all react quite differently. I made a simple change to the circuit. I wired the LFO to be full depth all the time. Then for a depth control I put a 250K (100K worked very well too) pot in parallel with the LDR and I found this gave me better control over the depth.

For reference my circuit was basically Jon Patton's Blue Warbler without the envelope section. Instead of a switch for tremolo mode I used a 100K pot with a built in switch which allows for a lot more variation in the wobble.