Magnavibe vibrato/tremolo blend mod for rotary speaker effect

[Kipper4]

Hey Ben
Is that POS slow enough yet?
And for information to build just one of the lfo's for the folie a deux you would need just u2c and u2d and associated componants.
Dual op amp 6xR 2xcap 2xpot 2xdiode and a switch.
Ooops and an LED for the Vactrol.
I hope you get it sorted mate.

[duck_arse]

todays updated circuit, both colours:
http://i.imgur.com/ttV7WpH.png
no colours:
http://i.imgur.com/vZGuVNv.png

I've put as many of "the things" in the circuit as I can think of (although I thort of an uther connection today .... tomorrow's update?), but no switches. new depth method, too. I thimk it should be clear how to join the dots. go easy with the feedback pot, it can make you a bit sick.

the phase1 stage has a cap across the feedback resistor, calculated by 1/2*pi*R*f. the f in question is the highest freq of the lfo/psssso/osc, mine was 9Hz-ish. this is meant to take the yang outta the waveform, producing a cleaner sine wave. sounds nice, can get some double-speed effects, but you need to tune the caps in the phase sections. I'm still waiting for an adult to come and tell us how.

ben - the lyman PSSSSO- you should be able to just shove in a set of 4 caps the same value, and it should cover the full pot-range.

[Kipper4]

Where does stage 2 get its signal from please?

[duck_arse]

today, it should be fed from the "stage1_out" point. tomorrow (the connection I forgot to try), it may come from Q1 source.

[Ben Lyman]

Some observations in comparing the different versions I've tried on the BB:
In my V1 and a few others, the POS Qc gets v+ only thru the LED's and resistors.
In Duck's V24.1 from the other day it gets v+ thru LED's and resistors PLUS a 12k parallel. That resistor kicked my ass when I popped it in! Holy penguin bait, Duck Man! I instantly got so seasick that I almost puked up my kippered snacks!
It's not present in your V24.2 but then you also have something called an I.C. thing-a-ma-jig in there... so I don't even know what to do with all that... but thanks for making it white so I can print it.

My latest BB as seen in the vid was tested by my brother last night, he agrees the range is acceptable but I'm going to keep working on the values and see if I can get some more range out of it. If I can get a nice range of speeds from slow to fast, I might want to work on the depth range. DM123 double LDR phase stages maybe? Is that the trick to making the pitch bend way over?

[duck_arse]

ben - in your vids wit der two blue lights, they look to be inconsistent/missing/odd beats. is this just from camera artifacts, or do they really go inconsistent. and are you yet happy with the range on "the new"? if your 1uF's are too slow, drop the 68k and the 82k both to 56k, maybe.

did you get any coffee yet?

[edit :] finally, he's seen the light. boom-tish, again. actually, the 12k is there giving the V+ to the collector and doing all the work, all the other junk is just hanging on extra. seesick, huh? wait till you go double reverse two stage with full feedback.

[Ben Lyman]

Wow! I think you're right, it might be defective, I'll have a listen to it later, hopefully just camera artifacts, whatever those are.
I want the thing to go really slow when turned down at the slowest it can go but I also want to be able to turn it up really fast. Right now the 2k2 stopper is as fast as I can go, with a 2k stopper it stalls out before it reaches top speed.

Do I need BC549 to make your version? Right now I'm using MPSA18, or would a 2n5088 work just as well?

[Kipper4]

Oppy amps ain't so scary Ben.
I haven't breaded the dub1 vibe yet.
The 12k collector is cool. I'll prolly put that in all future models. It strengthens the POS.
Keep those kipper snacks down dude.
As for the higher speed I could be wrong but I suspect the led is flashing so fast you can't see flashing, it appears to be full on all the time.
I'm awaiting email response on some stuff from DA.
I have a sea sick project for you both in development. More Kipper goodness in the sea.
Be warned op amps involved. Ben mate I'll give you some guidance on how to breadboard it.
Ducks not always that keen on oppys either.
The lfo on the new addition goes that slow between pulses that the missus had time to make me a coffee this morning.
Put the bloody flags out. I'm gonna savour every drop.
Refreshed and ready for my day off. National holiday. Yip yip.

[Ben Lyman]

Well, this POS is getting closer, going reasonably slow now and top speed is acceptable. I have 4 1uF caps with an 82k and 100k plus the 250k pot and a 2k stopper. Turn up the speed to max and it is right on the verge of stalling, which I think means I would have to use these very same pots and resistors right off my breadboard if I build it... or use a trimmer in there somewhere.

I don't think it's just speeding up to the point that I can't see it blinking, it's more like it goes from kinda fast at the full turn, then if I wait a couple seconds it starts to just get brighter until it simply stays on.

I am trying a A100k for the roto knob. Might as well use it if the knob is going on top of the box because the user then has a choice to crank it to full on tremolo, pretty choppy too.

My double waggler does have a a stutter... oh well, I guess I should get busy making a new board for it.

[bluebunny]

My double waggler does have a a stutter...

Out-of-context quote of the day.   

[Ben Lyman]

My double waggler does have a a stutter...

Out-of-context quote of the day.   

I wonder if it's cuz I put my two LED's parallel instead of series? Anyway, since reading duck's advice I have them in series on the BB and it does work better, no stutter so far, and much more waggle too!

[duck_arse]

BC549 - I just pulled mine out, and it measures 250hFE, so probably one of the most ordinary (lower noise) transistors around. any B or C BC54x transistor should work, or your 5088/9's which I am unfamiliar with.

and if your led is "....then if I wait a couple seconds it starts to just get brighter until it simply stays on." your oscillator is dying and stopping. this is how they do it, generally. the 82k and 100k can both go down some, and should help. but if you still have less than 10k in the vactrol led's stopper, it's going to mess with the speeds. show me your full oscillator circuit, with values, and I'll give it a go on the bb. nothing else to do.

two leds in parallel - but always a CLR for each, or they will fight.


americans puking kippers - our work here is done.

[Ben Lyman]

Ok Duck, I'll draw it up ASAP.
I see a few things that might need changing now that I look closer, lemme know what you think.
EDIT: Whoops, R18 is 270k, obviously I had some trouble thinking that one out, I meant for it to be 470K. I'll fix that on the BB and report back
EDITEDIT: Nope, seems maybe I tailored my circuit around that R14/R18 pot/resistor combo. For R13 stopper a 4K7 keeps it going at top speed, but top speed is just a little slower than superbadassness

My dad used to keep our pantry fully stocked with cans of smoked oysters, sardines in mustard or tomato sauce, and... yep, kippered snacks... mom couldn't stand it... history repeats itself, neither can my wife... sorry babe...

[Ben Lyman]

Here's the updated BB schematic. I've gone over it several times and I'm pretty certain it's correct.
I now have 2K7 for R13 stopper, next value down made it stall out so 2K7 is the compromise. Top speed is acceptable, slower speeds have lots of good pulsating action.
R15 "Trem" knob starts with pitch modulation only, then blends the tremolo in with it, then far side is only tremolo, pretty nice too, but not super choppy.

[duck_arse]

here: http://i.imgur.com/sfOfpZP.png

and here in colour: http://i.imgur.com/6tGyf1a.png

Mr Lyman, please try those values, tell me faster, slower, just right. also tell me what value caps you have (1uF, 820nF, 680nF, 560nF, 470nF). I was using electros, so I have one fixed leg going to V+, but for those playing along using poly's or plcc's, take that leg to ground. values shown gave a full 500k pot range (!) with no stall, and minimal droop. I dunno what taper you'd use, tho.

erm - everything changes the speed ranges - transistor hFE, feedback value, fixed legs, the 12k. and the current through the led string not only shifts slightly the speed, but also affects the dying, in a bad way. I tried a BC549, then threw in a BC548B, ~250, so any transistor better than "really ordinary" should work.

so for a single phased led, this osc works good. but, if you look the anti-phase leds 24.2 schem variant, the osc drives the opamp, so doesn't vary with led brights. it also ends up a much cleaner sine, less yang.

nice vid, again.


the "great, great" Lou Christie also worked on a two stage vibe, he even wrote a song about it ...... WARNING: may contain some falsetto.

[Marcos - Munky]

I really liked the last video. Just curious, what if you blend the output signal with the clean signal?

[duck_arse]

marcos - have a look at the circuits in reply #81, above. that shows nearly all the inputs and outputs you can use, join togther as you like. you don't need to have the two-phase led flashers, you can just flash one led at two ldr's if you want the simple life.

"the last video" - I take it you mean ben's, not lou's?

[Ben Lyman]

Duck, thanks for the explanation.  Little by little, I am learning more and more.
Closest cap values I have to those are 470nF and 1uF, nothing in between.
I am using 1uF monolithic ceramic but I also have some electro's on hand if needed.
I will alter my circuit as you described and see how it goes, thanks for that.

Marcos, from what I understand, the Uni-Vibe "chorus" setting is just that: blending a dry signal into the wet, so I tried it a few times awhile back with not much success. I thought it would make the effect sound like a chorus pedal but I couldn't make it do very much. It still may be worth a try for one of you guys who knows more about how to do it, I just want to keep the parts count down as much as possible.
BTW, the circuit I posted above also needs a make-up booster stage, I will probably just use another LPB-1 like last time.

[midwayfair]

I really liked the last video. Just curious, what if you blend the output signal with the clean signal?

The signal at the base and emitter are in phase with each other.

The signal at the collector is out of phase.

This effect works by rhythmically blending the signal from the emitter and collector together. The more closely the signals are matched, the more phase cancellation is heard. The phase cancellation is heard by us in part as a pitch vibrato, but imperfect level matching (which is inherent since one of the signals is always partially blocked by the LDR's varying resistance) produces slightly different notches, which is what we hear as the "phaser" effect. Also, omitting some of the out-of-phase signal essentially does the same thing. The 100K pot* Ben added for his tremolo blend forms a voltage resistor with the load at the input of the next device, lowering the output of that stage, and causing less pitch vibrato/phase cancellation. My Blue Warbler uses a switch for going to tremolo but a switch is obviously incapable of blending.

Blending the input signal would, in essence, be exactly the same thing as blending the emitter signal as the effect already does, with one important difference: the guitar will not be buffered by the transistor in such a case.

*I'm going to hop in here with a couple suggestions.

1) The blend is slightly unpredictable as wired. You also have no pulldown resistance. A single resistor at the output (e.g. 100K) (a) sets a predictable cutoff frequency for the output capacitors, so that they sound the same regardless of what amp or effect this is plugged into and (b) will prevent switch pops when you hit the bypass.

1b) Even better would be adding a buffer after that stage so that the impedance is guaranteed to be constant. FWIW, given the nature of guitar circuit impedances (usually between a few hundred K and the 1M of an amp), smaller resistances after the LDR will both be less variable (50K||1M is a much smaller difference than 1M||1M) AND will produce a deeper variance in effect. 100k is a decent compromise with the VTL5C1 but the ideal value depends on your LDR.

2) IMO it's better to use the LDR to vary the collector output rather than the emitter output if you're going to have a tremolo mode. Why? Because you can produce a small boost by very slightly decreasing the resistance on the emitter. Nothing major, just something like 6.8K instead of 7.5K. As it stands, the tremolo mode has signal loss because the emitter is never at exactly 1x gain and the LDR reduces it from there.

3) The depth pot, as wired, has a very limited range, which you found out a few posts ago. You can't go too high with the resistance or the LFO craps out. It also can't go to 0 depth without shutting off the LFO. It also affects the duty cycle, and affects the total speed range you can achieve at different depth settings (you want the collector resistance to be FIXED, not variable, to get the maximum possible speed range), and IIRC the rate indicator LED blinks backward to boot. There's a fix that reworks how the LFO works -- you can see my way of doing that here -- it's only a couple extra parts for the LFO and corrects every issue with PSO LFO in this effect (except the inherent speed range limitations of this kind of LFO).

Can't really comment much on the "rotary speaker effect" aspect of this effort, except to say that trying to get a rotary effect out of a single stage phaser is quixotic -- a rotary speaker cabinet contains a drum and two horns, with the drum and horns rotating at different speeds and affecting different frequencies, which is much more than a signal transistor can handle.

[Kipper4]

Ok you wombat sniffer  with you 18k what the heck.
i made my pso into vers x 2
like this
http://i.imgur.com/6tGyf1a.png

but i didnt have an 18k so patched some in series close enough to not be scientific.
I didnt like the 100k depth pot so i changed it for a 50k. sounds better to my ears.

using all box 1 uf caps x4
all leg resistors going to gnd

edit;
i left the 1M5 from C to E.

i like this version it is smooth and has a nice wide range of speeds as slow as id want to go and as fast as I'd need.
Aint you a clever clogs.
I go now do some antiphase led stuff.
thanks.
I think Ben will like how slow it goes too.