Magnavibe vibrato/tremolo blend mod for rotary speaker effect

[DMichel123]

Hmmm... I never tried doing opto trem on my design. What values are you using for the pot and LDR? I would think that if you simply replaced the 2M2 resistor at the input with a 1M pot and used a 5M+ (dark) LDR, you would still have full volume on the up swing of the trem modulation.

[duck_arse]

.....
following from your trem idea, and what I put on a switch in my above circuit, and Ben's "Lyman pot"/kipper's "trem/rotary" control. that pot will work as the series resistance for a shunt trem, if you hang the tremming ldr between the rotary pot and the lyman cap to ground. it just might work.
....

I am a goose. coming from the collector, the ldr to ground will mess with the DC, and we can't have that. so it would need another cap between the DC and the ldr.

as for what value, it depends on how deep you want, how bright you can go, how low your ldr swoops. with a GL5539 shunting a series 22k ~ 47k, and a superbright led, you will get A LOT of pinch. I haven't yet gotten to trying either of the two depth methods I can think of, one of which is the lyman pot mentioned.

[duck_arse]

I've been trying to convert this circuit to use valves - that's a different story tho - and it isn't working yet, so I had to put the transistor version together again to hear what it was supposed to sound like, and try summa the collected mods.

messing with the oscillator - ben, if you want a longer knob, you can add a fourth phase stage. I added a fourth 680nF to the string, with one fixed leg 56k and one 68k, and a 250k pot w/ 2k7 stopper, and have full pot range. it works, but I'm not using the standard dimmer/depth pot, mine runs parallel with the collector resistor, which also afects the stoppings.

and, perhaps the easiest mod-to-trem with the base circuit, is to simply open the connection to the cap at the collector. (I can't remember, is that one of kipper's?) it produces a VERY chopping trem, and about nothing else, I heard v. little depth change.

[Ben Lyman]

Thanks guys, I've been busy with boxing it up.
Duck- I'm very interested in the 4th stage addition but it will have to wait until I start over on one of these later.
My kids are bouncing off the walls so I don't have much spare time right now but I made a short vid. As promised, something special for this one. Depth, volume, and mix controls are on 3 trim pots:

[Kipper4]

Good work Ben the rotary mod works well.
If you set the trim pot for the rotary static you could just meter the trimmer setting and replace it with a set resistor of nearest value for a cheaper mod.
Good work man.

[robthequiet]

Yup, sounds cool! Has a nice throbby vibe.

We need a thumbs up smiley.

[Ben Lyman]

Thanks guys. Ya kipper, I was thinking for my purpose about 5k-10k sounds about right for the trem mix trimmer, so maybe I'll just make a decision and put a resistor in next time. I dialed the depth trimmer down a little because I upped the speed with that 1.2k resistor, and with that at top speed the depth needed a little adjusting. I like where it's at now, two speeds and both sound pretty good wherever I set them. Less knobs equals more music!

[duck_arse]

so the second footswitch is just selecting speed pot a or speed pot b?

I'm mighty impressed by that double-humper resistor, the lyman rotator, the kipper collector, what the hell is it called? it does mean I have to rethink my switches tho.

[Ben Lyman]

so the second footswitch is just selecting speed pot a or speed pot b?

I'm mighty impressed by that double-humper resistor, the lyman rotator, the kipper collector, what the hell is it called? it does mean I have to rethink my switches tho.

Yup. I just ran a wire from the board to the DPDT middle lug, outer lugs each go to the CW lugs of the speed pots (all CCW and wipers to ground)
The blinking LED's share a connection to the vactrol and a connection to the DPDT. I had to draw a pic to figure it out but it looked like a toddler's depiction of a bird's nest. I tried to redraw it yesterday and this was the best I could do.

[Kipper4]

What value pots are you using for the two speed pots please Ben?
Thanks.
Kipper collector. Ahh no.
It was all Mr Lymans work. I just trialed it on the breadboard for him to see what value I liked best.
Great work Ben, you should be proud.

"Less knobs equals more music!" Not what you want to hear is it D.A.?

[Ben Lyman]

Kipper, speed pots are both B50K, I was trying to go as slow as I could without killing it and that's what I came up with. Hopefully one of you can do better, I like the top speed (w/1k2) but it would be nice if it could go real slow too.
Duck, is that what you meant by "longer knob"? ability to go slower and faster? Because I thought maybe you meant something different... 

[Kipper4]

Thanks pal.

[duck_arse]

more knobs! add some switched caps!! put more parts!

ahem. yes, ben, a longer and wider knobbage range is exactly wot i ment. I've got the new! improved! 4 phase version running from ~ 9Hz to ~2.5Hz, using 250k and 2k7. "C" would be better, but I'm "A" taper backwards at the moment.

it strikes me that you could put a low value pot in for a wider band-spread fast side, and a larger stop R and bigger value pot for a slow range that doesn't overlap too much. it would mean a lot of fiddle. let me know if it sounds like a thing, I'll maybe work some numbers.

[Ben Lyman]

...a low value pot in for a wider band-spread fast side, and a larger stop R and bigger value pot for a slow range that doesn't overlap too much...

Sounds like a great idea Duck, like I said the fast side goes plenty fast but it would be nice to get some really slow action too.

In a perfect world, my pedal board would have nothing but footswitches and all the parameters would be perfectly preset so I never have to adjust anything 

How's the 4-stage sounding? I really want to try that out but can't get back to the magna vibe yet as I just BB'd the JFET Vulcan again

[duck_arse]

the 4th stage is just an oscillator mod, doesn't affect the sound. there is plenty other things create madness in there. try putting a 10nF~22nF cap between the emitter and the ldr. gives you the hump.

surely, both you and kipper have a breadbord dedicated solely to the magnavibe, non? a constantly-built test bed you can just reach out for?

[Ben Lyman]

my BB station is kinda limited and it's all sticky-taped down together on one big platform so I always have to rip everything out when I start a new project 
I just might rip the current JFET Vulcan off and go back to the Magnavibe, this extra stage has intrigued me... and now your "hump cap"... hmm...
I have read your description of it several times but is there a chance you can post a schematic of that addition? even just a pencil sketch or something of the sort

[DMichel123]

For slower LFO speed, I used a dual-gang 20k pot to alter two legs of it at the same time. I haven't measured the frequency at the slowest speed, but I would guess it's down below 2Hz.

I am building these pedals commercially, so I hesitate to share all my "tricks". I'm very new to pedal building, but have worked with tube circuits for 15+ years.

[duck_arse]

for lyman eyes only:

http://i.imgur.com/7QVByPp.png

this is where I am at currently, a buildable version. shows the "new" version of the pso, w/ 4 phase stages. please note the different led connection. I run the osc full tilt always, and just vary the current available to the flasher leds. the rate led can also be seperated, to blink full brites instaed of vactrol following.

[DMichel123]

Duck, I took a peak at that schematic... 

Since I peaked at that, I will share another trick I used on mine. Coincidentally, I have a 2N7000 at the same stage of my circuit. It is biased for unity gain and I have the LFO modulating the bias in trem mode. Like an EA trem.

[Kipper4]

I tried the 50k speed pot with the 1k5 resistor mod and without. Too slow for my liking. It practically stalled the pso. I'm using white heatshrink on my permanant breadboarded version of the mangledVibe.
I still prefer my 10k speed pot. Sorry Ben.

I tried the 10nf Humpty Dumpty cap. I couldnt hear Jack difference. I tried a 20nf Humpty cap, I could hear it a bit more. The jurys still out on this one because it kinda killed the vibe which was the whole point of the thang. Sorry D.A.

I'll be intrested to see what Ben and DM123 have to say about it......

Don't you just hate it when someone puts loads of full stops after a sentence?