On the breadboard now. Just experimenting.
image deleted see my next post
shouldn't dry signal (220nF I cap) go to IC4b inverting input (via 10K)?
Sorry Yes Fender3D
It's the wrong image anyway Heres what is really on the breadboard.
(http://i.imgur.com/5Or43ZK.png)
there's something very wrong with your I cap wiring. Q4 base seems to be connected hard to the output. I'm off for a listen .....
yep sorry again guys theres a 100nf cap between the Q1 source and Q4 base.
I'd add a mix/buffer @ output, just in case...
Even a simple thing just like P90
Thanks Fender.
Theres more to come hopefully. I'll update as progress is made.
I'm already happy to have made this work so thats a positive.
Stay posted.
Theres room for improvements still such as fenders excellant suggestion and you guys can keep this coming.
Heres ver4 schematic (or something similar)
(http://i.imgur.com/Y351Dov.png)
Intended more as fuel for the fire than as rain on the parade, the traditional tradeoff in modulation is that faster modulation rates want less sweep width. Indeed, many would argue that the reason for including a Depth control at all is simply because the range of speeds is so wide that no single sweep width works for all speeds. MXR and EHX, as well as so many copiers, went with a single fixed sweep width for the earliest phasers, that was deemed as an acceptable one-size-fits-all solution. Actually, I'll correct that. The Small Stone cleverly built in a change in both speed range and sweep width to the Color switch it included. But it wasn't continuously adjustable. While two allpass stages is not going to get you boy-yoy-yoing vibrato, one may still feel some sort of compensation for faster speeds is needed.
Sometimes, that is provided by the properties of the LDRs themselves. That is, the LDRs may be sluggish and not respond to faster changes in luminance, such that slow speeds get you full sweep width, and fast speeds get you something much less than that. The old CLM6000s were sort of like that Unless one can make some very specific recommendations for LDR, in a DIY circuit like this, there is no assurance that faster LFO speeds will be accompanied by a suitable change in sweep width.
Which leads me to the following suggestion.....
Make BOTH your speed and depth set by some combination of LDR and parallel resistance. Your foot treadle, now controls the resistance of two legs of a pot in reciprocal fashion. Heel down, the current limiting resistance for the Rate LDR goes high, slowing down the LFO. At the same time, the current-limiting resistance for the Depth LDR goes low, brightening it and increasing the LED luminance on Vact-11B and 12B. Toe down, the Rate-LED current-limiting resistance goes low, speeding the LFO up, but the Depth-LED current limiting resistance goes high, reducing the luminance and making that Depth setting higher resistance.
Admittedly, its a lotta LEDs and LDRs (four of each) but it could get you a smooth treadle functioning that automatically adjusts width as you go faster. Naturally, it would require tinkering with the value of resistances in parallel with the Rate and Depth LDRs, so as to achieve a pleasing and musical transition from heel to toe down, as well as wise choice of the physical pot controlled by the treadle, and any resistances in parallel with each of those pot legs to achieve the desired change in LED luminance.
One perk, in addition to automatic depth/width compensation is that any potential noise from momentary discontinuities in the LFO circuit would be absent. The only moving part is associated with control of luminance of the additional LEDs.
Cheers Mark.
I'll reread this a few times to get a fair grasp of it.
I guess the second output of the treadle could be used as a variable resistor for the depth of one side of the effect. (2 phaser stages).
Its far from perfect and pretty far from what I would like to achieve.
I was kinda hoping to get that interactive wow and flutter effect you get with a leslie cab.
Also It might seem like a lot of vactrols too, I'm certain i can trim down the amount of leds by half by making discrete 2x ldr per led vactrols if I ever build it.
I might even change direction and go for 4x series phaser stages with 1x led controlling 4x ldr all with the speed controlled by the treadle lfo.
I'll go look at the small stone meantime.
Thanks for the fuel.
The Small Stone will be an unproductive distraction, since it uses an OTA-based LFO, which is not relevant here.
At the moment I'm running all four phase stages in series and it sounds ok.
It does have some issues.
The op amp non inverting output make up gain stage (gain of 5) isnt helping. Creating some noise.
Its a bit thumpy. I suspect lfo tick?
If I play hard it seems to unbias the input? solutions sought please.
The clean feedback path is ac coupled to the output mixer (series 1uf) after the I cap.
I'd like more control over the amout of clean gain. How best do I achieve this?
Further thoughts.
I'm considering using the volume pedal to control the speed of both lfo's simultaniously but both lfo's would have the speeds offset a little.
I thought I'd put different sized series resistances IC4A output and IC1A output (ref last posted schematic)
The reason for the speed offset is because thats how it sounds best to my ears, When the speeds are similar but not the same.
Thanks for taking the time to read this and any help will be appreciated
Rich
Edit. I forgot to ask how do I put some small caps (eg 50pf) in the phase stages like some of the op amp phaser stages ergo the bi phase?
Update oclock. Well just gone midnight really.
News just in.
I cant use a single volume pedal with two lead on the outputs to control the speed of two independant lfos.
Unless I wanted a junky effect.
Basically one of the lfo's stalls for a bit, jumps back into life, and the output of the lfo also is way stronger than normal. Suggest a rush of currant given that my retina are burning.
This might work as a dance dj's effect with built in laser but as a rotobox its near useless.
Back up a bit and replan.
It'll be kipper time before I know it.
Wheres Duck at? Surely it must be sun up in the Antipodese.
:icon_idea: :icon_idea: :icon_idea: :icon_idea:
I guess If you had an old wah shell or busted volume pedal you could swap out the pot for a dual gang pot and do this ^ though.
Have the feedback path on a switch and go Vibe or phaser......
"Edit. I forgot to ask how do I put some small caps (eg 50pf) in the phase stages like some of the op amp phaser stages ergo the bi phase?"
Do I just put them in parallel with the 4M7 resistors?
Having investigated the treadles limitations.
I decided to go a little more tradtional but keep the dual lfo.
Heres ver 7 with demo to follow.
Of course you could simplify it by only using one lfo to drive a discrete vactrol, 1led driving 4x ldr bunched around the led,
(http://i.imgur.com/pOzkD7T.png)
Please note although the drawing say ver5 the last post is in fact ver7
Demo
Rich, that is the coolest thing ever!
I might have to repost my ad for "Wanted: Broken Wah Pedal"
Sweet man. Glad to inspire.
One could do a depth mod on the treadle pot to go between totally dry through phaser to full vibe.
By hooking up clean pot to the treadle.
Option 2
Speed on the treadle.
Option 3
Depth on the treadle.
Note a new feature the 100pf caps which I haven't tested yet for oscillation with an overdrive pedal behind it.
Because I had an issue without them.
SteveO say you have 3 vibes already.
(http://i.imgur.com/mATQSAb.png)
plug the speakers, unplug the speakers. plug the speakers, V8, V9, V4. unplug the speakers. where'd the other two stages go? still 2 oscs? no treadley?
sounds like it's chewing something, Wavey Davey. tweet tweet.
See my last post, schematic included
2 stages, no treadle. no fuss.
It's chewing Phase friends. Eat it and weep.
Whatya think of the clean/phaser/vibe pot?
I thought it worked well.
Don't unplug your speakers there will be another right along soon.
Another wheel to reinvent. :icon_razz:
Edit. It works even better now the clean pot has its own 10k to op amp input.
That cleared up the noise issue. Thanks SteveO. Still some clean ups to do.
Keep those speakers pegged.
Quote from: Kipper4 on September 15, 2016, 01:10:11 PM
Edit. It works even better now the clean pot has its own 10k to op amp input.
That cleared up the noise issue. Thanks SteveO. Still some clean ups to do.
Yeah, I was going to mention that too. With that inverting amp on the output, it makes sense to use it as a proper inverting mixer. Did you get rid of one of the caps in the clean path too? You had a 100nF DC blocker at one end, and a 1uF at the other - don't need 'em both. I'd also use the "clean" pot as a level control with the bottom of the pot grounded and the wiper taken to your mixer resistor, but perhaps your "variable gain" method is preferred, dunno. Do you really need x22 gain to boost the level at the output? Seems like the signal must have suffered on the way through if so. I'd want to boost it a bit on the way in to improve the signal/noise ratio, rather than boosting it (and any noise) after the effect. Finally, you could put a little tiny cap across that 220K feedback resistor in the output amp, just to limit the frequency response and stop any crazy RF oscillations the op-amp might wonder about getting into on its bad days. That can help keep noise down too. 22pF would give you a 32KHz roll-off.
Good luck from here on!
Tom
Still some work to do here. Planned for the upcoming week.
Thanks guys.
A little updated schematic and demo.
You guys have to be getting bored with this one already but I'd appreciate your eyes and knowledge to see if anything can be further improved or if theres still any bits I could remove.
The blend works ok but I think I might try a different taper. Suggestions on this please.
(http://i.imgur.com/U0nIUKx.png)
The blend pot is a audio level control, so the theory says a log pot should be best - we hear in decibels and all that. What have you got?
Tom
Oh, and shouldn't that 220nF (B2) be the other side of the pot?
The pot is grounded, but the amplifier is biased to the midpoint. I'd have thought that means the cap needs to separate them. Whereas the Q5 stage is grounded the same as the pot.
Alternatively, you could take the bottom of the pot to the Vb I suppose, but I don't like it. Dunno why exactly, but it doesn't feel right.
HTH,
Tom
Sounds good Rich.
Can I ask a big picture question? Do you really need a depth and a mix and a volume control? I can understand 2 out of three. Maybe. As it is, you can't get a wet-only signal...
Also, you are not asking much of VB here, so why not use the IC4A as the input buffer?
And, have you considered staggering the caps in Magnavibe-ish stages to make it a little more Univibe-ish?
"Also, you are not asking much of VB here, so why not use the IC4A as the input buffer?
And, have you considered staggering the caps in Magnavibe-ish stages to make it a little more Univibe-ish?"
I tried the other half of the op amp as the input buffer (inverting set up)
It sounded much less hifi. It works but sounds nothing like as good.
However using a non inverting input op amp buffer is fine.
Thanks thats a few less parts and space.
I have changed the second lyman cap (L) to a 47nf. Should i try some different values. If so which?
Thanks Tom
I made a few other changes thanks to your suggestions.
Schematic coming up.
I ditched the 100pf caps they were choking the phase pretty much.
Thanks Guys and Thanks D.A.
Further suggestions always welcome.
(http://i.imgur.com/GZIcvQk.png)
Eratta
resistor 27 should be 33k not 47k
Heres a similar version with an alternate p90 style lfo shown.
And some differing vactrols. that suit more common parts for stompboxers.
Also note the resistor for the dry path at the op amp input (3) value has changed to 24k. 22k will work also as well.
I'm reserving judgement on using the volume pedal as a speed control hooked up via a switched 1/4" jack. (LFO1 only)
(http://i.imgur.com/fQqak6F.png)
I'd lower R26 (1M) to 47K~100K and use IC3's pin 3 as an alternate (switched) input for R38.
You may taste in phase or out of phase... phasing :)
Great Idea Thanks Fender3D.
Now I have a dilema. The phase mode is lower output than the Antiphase.IIRC
How do I compensate for this?
Volume pot at output? This probably wont work as one mode is below unity.
different gain resistors (Rin,Rf)?
pot in the place of R27?
It sounds amazing.
Hold the posts.
I think I have it.
When switching vibe inputs I have to switch the dry input too.
So DPDT. Snippet coming up.
(http://i.imgur.com/qv3Fy81.png)
In a differential amplifier you'd use R2=R38, R3 and R27=R26
If all the resistors are all of the same ohmic value, that is: R3, R38 = R2 = R27 = R26 then the circuit will become a Unity Gain Differential Amplifier and the voltage gain of the amplifier will be exactly one or unity.
Brilliant thanks Fender.
(http://i.imgur.com/po2c4xN.png)
I found if i make R4 less than 10k it oscillates.
Is that what you wanted? That switches the phase of both signals, so it's equivalent to leaving it how it was, but inverting the whole output.
I thought you were aiming to just invert the phased path, in which case the dry path could switch input resistors to keep the levels similar, but doesn't need to move to the other op-amp input.
Have I got the stick by the wrong end?
Tom
Yer your spot on Tom.It was a quirk of the breadboard making me think otherwise.
I need to change a few values but otherwise its done.
That 2nd ph
asestage gets loaded quite a bit!
Please elaborate Snap or anyone else.
Do I need a resistor between phase stages?
you need a higher impedance after the point where LDR and cap unite.
So a bigger blend pot? or bigger R38.
I thought the op amp impedence was basically set by the 1M to Vb.
Quote from: Kipper4 on October 01, 2016, 07:28:08 AM
I thought the op amp impedence was basically set by the 1M to Vb.
Inverting op-amp's input is a virtual ground, then its impedance is set by R38.
R26 keeps +input "open2 allowing you to feed another signal on + input.
What snap says is your Vact+R21 is affected by Blend+R6
Quote from: Fender3D on October 01, 2016, 10:10:17 AM
Quote from: Kipper4 on October 01, 2016, 07:28:08 AM
I thought the op amp impedence was basically set by the 1M to Vb.
Inverting op-amp's input is a virtual ground, then its impedance is set by R38.
R26 keeps +input "open2 allowing you to feed another signal on + input.
What snap says is your Vact+R21 is affected by Blend+R6
Well, yes, R21 doesn`t care *that* much though, but the combined, phaseshifted signal at the vactrol/cap-output is very "fragile" and screams for being buffered somehow.
Ok thanks so It would be more stable with a buffer after the 2nd phase stage output and before the blend pot.
It's still on the breadboard I'll stick a bjt buffer in.
Cheers
Thanks Guys for the advice. It is defeinitly worth the extra parts.
nice to see the winky led in shot, I find it provides more information about what I'm not/hearing in clips. sound good.
when you say "switch to antiphase", what is it you are doing?
Just this
(http://i.imgur.com/ilnd7gZ.png)
Quote from: Kipper4 on October 06, 2016, 10:08:09 AM
Just this
Why don't you use a 10K pot instead of R19?
Won't that misbias the transistor and add some horrible noise to the signal?
If not. What does it do?
It had'nt occured to me that was even an option.
It looks to me like a trimmer for R19 will allow you to adjust the "wet" output.
Oh I'm following now.
So an A10k lug3 to emitter, lug 2 to capK, lug1 to gnd.
The transistor is always working the same as the 10k series resistor.
but the pot put signal to output amp or not depending on rotation.
Works great on the breadboard too.
Thanks guys one part less.
Back to the layout.
Thanks
Larry this thing has so few pots it's nice to have the wet dry pot outside of the box.
R19(10K) and the Blend pot (25K) in parallel gives a 7.2K result, so replacing R19 with a 10K pot does adjust things a little.
I doubt it matters though, so go with it. Just thought it was worth mentioning.
HTH,
Tom
The only issue I have with this now is that when phased and dry sigal both go to the non inverting input theres a certain amount of dare i say it phase cancellation.
IE It's a lot brighter.
Now do i try to combat this with a low pass filter on the phased signal when it goes to the Non Inverting input only (extra cap to Gnd after R21) or some other solution.
It sounds ok if i just roll the guitars tone pot back a bit. And still sounds different enough to the opposite mode to say theres a definite change of sound and feel.
Suggestions please.
Quick fix schematic. New low pass filter with cap H1
note theres a new value (4u7) timing cap in the lfo.
different value resistors going to the output amp. All now 33k.
and different phase stage mix control as suggested by you guys Q1
Thanks a bunch fellas
(http://i.imgur.com/zOUOuS5.png)
Quote from: Kipper4 on October 07, 2016, 12:24:44 PM
note theres a new value (4u7) timing cap in the lfo.
I didn't noticed it before...
I think it should be BP (or non-polarized)
I dont have non polar.
Its life may be limited i guess.
You can use two polarized caps to make a bipolar.
Connect the negative leads of two 10µf polarized caps to "make" a 5µf non polarized cap.
The two "positive" leads connect in place of your 4.7µf integrator cap.
Cheers guys maybe in future I'll use the back to back 10uf
I'd rate that your best switch yet. and the budgies like it, I can tell.
Quote from: duck_arse on October 09, 2016, 09:54:32 AM
I'd rate that your best switch yet. and the budgies like it, I can tell.
That was Fender3Ds idea and a great one too.
Them ain't no budgies. It's condors.
Wait till you see the other enveloped phaser. Same theme. Keep you eyes peeled for more condors in the picture section.