New Phaser Design - “Causality 4” – Built with you in mind!

[bluebunny]

Mid build  causality 6 and I cant see how to wire the regen pot since I'm using the parity switch.

It's in there somewhere, mate.  I have a local copy of the C6 board and wiring diagram.  Either side of the parity switch (odd and even) go to the pads in the bottom left (if you're using Rick's board).  The common terminal of that switch goes to Regen 3.  The only other Regen connection appears to be to lug 2, and it comes off the bottom of R40 in the middle of the board (which is a 10K).

Edit: it's here.

Edit #2: watch out for Rick's caveats on p16!

[Kipper4]

Thanks Marc
Good catch.
Now for the will it won't it phase.
Did you see what I did there 
Cheers

[bluebunny]

Don't give up the day job, Rich.   

[Kipper4]

So maybe unbook my half hour slot at the comedy store then.
Well that was fun debugging and I'm not done yet.
I might have to implement the Vref using 78l05

[Kipper4]

Another afternoon debugging and i'm no nearer. frustrated now
Rant over

[Kipper4]

C6
I've been over everything with the meter to check continuaty.
I've checked the lfo output with the scope.
one sub instead of TL084 im using TL074
I'm at my wits end after another evenings debugging. it's 2.30 am
I've just done the 78L05 cludge. I'm off to bed.
I'll check if it has worked in the morning.
Otherwise expect a new thread entitled debugging the C6.
Night John boy...zzzzzzzzz

[Kipper4]

I take that back my lfo isnt lfo'ing.
plus im getting guitar signal on it at lfo output......

[Kipper4]

The fecker is now.
I had a solder bridge on the lfo output.
Now i can get back to the parity switch mod an phase/filter switch mod.
Thanks for letting me vent.

[Kevin Mitchell]

I'm really not one to relight old threads but I feel I should here;

I'd really like a many-stage LM13700 phaser I could wrap my head around and this fits the bill! Ever since I heard the deep-long swoosh of a Moog MF-103 I've been dying for an over the top phaser. I understand this is far from a Moog project but would anyone have any recommendations to make this compete with the MF-103?

I've been looking at the Causality 6 schematic and would like to triple the stages (how much is too much?  ) Though I'm a little confused to why the names like "Causality 4" seems to have 2 phase stages and the Causality 6 has 4. Is the name not relevant to the amount of stages or am I wrong here?

I see a few mods here that would be very ideal for this project but I'd still like some intel from the forum.

Has anyone here adapted this project beyond 4 stages (Causality 6)?

[Mark Hammer]

The number of stages that can add value to a phaser depends on what you're feeding it, and what you're listening to it through.  The same thing goes for the comb filtering of a flanger.

The challenge is that, much like a tree falling in the forest with no one around to hear it, a notch inserted to a frequency-band that the instrument/source does not produce, or listened to with a speaker that does not possess the requisite bandwidth, fails to impress.

Having listened to white noise processed with a 24-stage phase-shifter, I can vouch that, yes, highly complex wide-bandwidth signals CAN sound staggering through yet more stages.  But, as many guitar players can attest, the flanger they spent good money on doesn't sound anywhere near as dramatic as the recording that inspired them to buy it...when they simply play their guitar through it...because the guitar lacks the bandwidth that the mixed-down multi-source recording that inspired them had.

I find that, for guitar, more than 8 stages tends to be moot.  Yes, I know there is a plethora of phasers with 10 and 12 stages.  I have a Boss RPH-10 with 12 stages...but a guitar through a guitar amp makes those top two notches inaudible.  A synth played through wide-bandwidth speakers will display an audible impact of those top two notches, because both the synth and the speakers have the requisite bandwidth.

BUt, but, but flangers have a lot more than a mere 4 notches, you say.  And you are correct.  So why can I hear a lot more than 4 notches in a flanger, but not in a phaser?  Simple; they are spaced farther apart in a phaser, and the lowest notches a flanger produces are much closer together than those produced by a phaser, as well as the higher notches produces in that very same flanger.

Personally, I find that 6 stages is pretty much the sweet spot for guitars.  It is a complex-enough change, plus the feedback path causes fewer problems, and the location of the notches is less problematic.  Adding more stages lowers the frequency range where the notches (and adjacent peaks) are located, rather than simply adding one more notch above where your current highest one is, and leaving the other notches where they are.  As well, one assumes that each phase-shift stage is unity gain.  But even using 1% resistors, there is still a chance that, when all the phase-shift stages are added up, the entire path has a gain greater than 1x. And when that happens, feedback/resonance has to be turned down so that oscillation doesn't occur.

Now, both problems CAN be fixed by: a) changing the value of the caps to nudge the range up a little and keep the woofiness out, and b) using a trimpot to dial back the resonance/feedback so that you can safely turn the feedback up full tilt without fear of setting off the siren, and c) sticking a small-value cap in the feedback loop of one of the phase-shift stages to tame any accumulated noise.

[Mark Hammer]

In the process of trying to finish up some pedals that had been sitting on the bench for too long.

One of them was a Causality 4 MkII that made the most obnoxious thumping sound.  I used an LM358 for the LFO, so I thought it couldn't be that.  I had also used an LM324 for the 4 audio stages.

Reasoning that the 324 might not be able to handle something about the circuit, I swapped it out this evening for a TL054 quad op-amp (the schematic indicates a TL084, but this was close enough, and I got a good deal on them).  Problem solved!

It still provides a nasty thump if one dimes the width and range controls, but you're not supposed to do that anyway.  It was easy to get a nice thump-free sweep by using those two controls judiciously.

[Kevin Mitchell]

In the process of trying to finish up some pedals that had been sitting on the bench for too long.

One of them was a Causality 4 MkII that made the most obnoxious thumping sound.  I used an LM358 for the LFO, so I thought it couldn't be that.  I had also used an LM324 for the 4 audio stages.

Reasoning that the 324 might not be able to handle something about the circuit, I swapped it out this evening for a TL054 quad op-amp (the schematic indicates a TL084, but this was close enough, and I got a good deal on them).  Problem solved!

It still provides a nasty thump if one dimes the width and range controls, but you're not supposed to do that anyway.  It was easy to get a nice thump-free sweep by using those two controls judiciously.

I've just tried to breadboard the Causality 4 using 22k instead of the 27k and 1k5 instead of 1k8. But there seems to be a error in the nest...

I used an lm358 for the lfo and a TL074 for the audio path, was tempted to used a lm324 there lol.... I'll try again - I think I have a TL084 kickin' around somewhere I'll swap that if the 74 doesn't cut it.

Do you think my resistor substitutions would be a problem? Also thank you very much for the intel! Great info.

[Kevin Mitchell]

I'm trying to choose the right schematic loaded with additional features and I see this one

Why is Rev10 -normal Causality 6 from 2009 and Rev2 -with additional functions from 2010?.... These revision names are confusing. I wouldn't want to build something from an obsolete schematic.

Also I've heard many times any more than 6 phase stages is not audible with guitar so I guess I'll do 6 and not 12 

[pgorey]

I may need to start a new thread here but I'm wondering how important it is to have the 47k and 470k pots? I'm having trouble finding them without spending a ton on shipping and they are not the most typical pot values.  Also, any issue with getting a 500v capable ceramic disk in for the 10nF cap?
Using this layout by the way (http://tagboardeffects.blogspot.com/2012/02/causality-4-mkii-rick-holt.html)  and have everything soldered up on the board and only missing the 10nF ceramic disk.  Need to solder on the pots and I/O and eager to put this one to bed.  Thanks and please let me know if I should start a new thread.

[Cozybuilder]

pgorey-
You can use 50K and 500K pots in place of the 47K and 470K

The 10nF is just in the feedback loop of the LFO- you can use anything over 10V rating.

[bluebunny]

. . . and they are not the most typical pot values.

Perhaps not in North America, but quite common in Europe.  Rick's a subject of Her Britannic Majesty and is domiciled in her realm. 

[pgorey]

Thanks for the feedback.  I used those pots (50 and 500) and it sounds great!  Love this design and the variety of sounds I can get from it.  I installed a trim pot to dial in the bite of the regen / drive pot and it sounds phenomenal.  Thanks again!

[Kipper4]

I use the causality 6. Great phaser.
I did mod it to remove the dry path on a switch though.
If I get a big enclosure free I should do an 8~12 stager.

[Mark Hammer]

If one plans to use it exclusively for guitar or bass, I wouldn't bother going past 8 stages.  The additional notches produced by adding stages tend not to be audible.

The other advice I would add is limit the low end in the feedback path, and use a trimmer to prevent feedback resulting in oscillation.  Phase shift stages are intended to be unity gain.  But 5% resistors being what they are, a given stage can produce a smidgen of gain (e.g., 5% less on an input resistr and 5% more on a feedback resistor yieldsa stage gain of 1.1x).  As one adds more stages, the risk of cumulative gain increases (e.g., 1.1 x 1.1 = 1.21), increasing the risk of oscillation

That increased risk of gain also increases the risk of noise.  Phasers using 6 or more stages often include a feedback cap in one or two phase-shift stages to roll off accumulating treble.  If a phase shift stage uses 10k input/feedback resistors, consider a 1nf-1n2 feedback cap in parallel with the 10k to roll off some top end while still maintaining the crispness.

[Fight]

Hey guys,

i tried this cool design, but couldn`t get it to work. The circuit works so far, but there is a massive volume drop, until I touch my finger on one specific point on the upper side of the board (view pictures). The volume then comes back until bypass-volume, like it`s supposed to be.

I have done a litle video, where you can see the strange behavior: https://youtu.be/izvq2eONoNY

Does anybody have an idea how to solve this problem?

Many thanks for your help,
and best regards

Veit