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

[gambit07]

yes, i think i came across that 4th victim too.. will try to breadboard (though i hate breadboards) to see if i can do something about it..or maybe use sockets on "modifiable" areas on my build.. will also let you know if something comes up.. thanks!

[MrStab]

from another (let's face it, the other) stompbox forum:

"sundgist wrote:
Taking vref on the lfo buffer/gain stage from the lfo's voltage divider causes the lfo to swandive just before it gets to each positive and negative peak. I've moved the 10k resistor and wire along a bit and added a link to the main power supplies vref."

assuming this is the problem, i'm pretty sure i'd tried stabilising with the main vref that way, only to kill the effect

[artifus]

from another (let's face it, the other) stompbox forum:

this reminded me of this: http://security.stackexchange.com/questions/33470/what-technical-reasons-are-there-to-have-low-maximum-password-lengths

Take five chimpanzees. Put them in a big cage. Suspend some bananas from the roof of the cage. Provide the chimpanzees with a stepladder. BUT also add a proximity detector to the bananas, so that when a chimp goes near the banana, water hoses are triggered and the whole cage is thoroughly soaked.

Soon, the chimps learn that the bananas and the stepladder are best ignored.

Now, remove one chimp, and replace it with a fresh one. That chimp knows nothing of the hoses. He sees the banana, notices the stepladder, and because he is a smart primate, he envisions himself stepping on the stepladder to reach the bananas. He then deftly grabs the stepladder... and the four other chimps spring on him and beat him squarely. He soon learns to ignore the stepladder.

Then, remove another chimp and replace it with a fresh one. The scenario occurs again; when he grabs the stepladder, he gets mauled by the four other chimps -- yes, including the previous "fresh" chimp. He has integrated the notion of "thou shallt not touch the stepladder".

Iterate. After some operations, you have five chimps who are ready to punch any chimp who would dare touch the stepladder -- and none of them knows why.

[armdnrdy]

Take five chimpanzees. Put them in a big cage. Suspend some bananas from the roof of the cage. Provide the chimpanzees with a stepladder. BUT also add a proximity detector to the bananas, so that when a chimp goes near the banana, water hoses are triggered and the whole cage is thoroughly soaked.

Soon, the chimps learn that the bananas and the stepladder are best ignored.

Now, remove one chimp, and replace it with a fresh one. That chimp knows nothing of the hoses. He sees the banana, notices the stepladder, and because he is a smart primate, he envisions himself stepping on the stepladder to reach the bananas. He then deftly grabs the stepladder... and the four other chimps spring on him and beat him squarely. He soon learns to ignore the stepladder.

Then, remove another chimp and replace it with a fresh one. The scenario occurs again; when he grabs the stepladder, he gets mauled by the four other chimps -- yes, including the previous "fresh" chimp. He has integrated the notion of "thou shallt not touch the stepladder".

Iterate. After some operations, you have five chimps who are ready to punch any chimp who would dare touch the stepladder -- and none of them knows why.

So if I read this correctly we're not supposed to install some chimps.......Which chimps are we supposed to leave out? 

[artifus]

i generally tend to avoid the ones who are not already banging rocks together.

[MrStab]

so, from what i understand, 2+2=5?

[artifus]

yep - do it to julia.

[MrStab]

moving on from the event that never happened, i put a 78l05 back in, no effect, and lowered vref to about 4.5V with a 1n4001 (not sure why i thought that would work, but i thought screw it, might as well try and simulate what it would've been with the divider), still nothing.

i have a severed wire from experimenting between where Shape lug 1 meets the diode to ground and the main circuit vref, which, if i touch together then separate, gives me one solitary sweep. doesnt seem to be any considerable difference in voltage between the two extremes. clue?
i'll keep mindlessly poking stuff as ever

[MrStab]

if i connect aforementioned wires, then turn Regen full, it squeals out the LFO rate, then when i put it back down, it continuously phases although weak.
Pin 1/output A of LFO opamp (tried a few different ones inc. 4558, TL072 and OPA2227) is consistently too high, even with nothing in the socket. 6-7V.

source voltage has drooped to 7.5V or something since switching the 78L05 regulated vbias attempt

[MrStab]

things i've tried:

• separating LFO IC's power and placing a 1000uF cap to ground
• separating the V+ of the LFO's voltage divider from the V+ on the quad opamp and placing a 470uF to ground (not sure why that would make any difference, but meh)
• Voltage-regulated vbias as previously mentioned

decoupling came to mind because the circuit "thumps" when speed is on full. anyways, no dice - while the sweep does seem a bit smoother, it's still lop-sided. the Shape pot at full CW & CCW and the speed LEDs give an insight into the disproportionately sharp rise of the sweep.

thinking i should just start over from another layout, checking as i go with the schematic, but it's a pain when there's probably just one fix.

[jimilee]

I got the same thing going on too,  for the squeel on the regen pot and sometimes distortion, i put a 2k7 on lug 3 of the regen. it helped with that, but still lopsided phasing.

[MrStab]

does your Regen pot only squeal when you turn it near full clockwise, jimilee?

having relentlessly trawled the web for solutions to various hardware problems for years, it's actually reassuring that quite a few of us seem to have the same problem. this phaser just sounds really, really cool even when it's not working properly!

[gambit07]

this phaser just sounds really, really cool even when it's not working properly!

+1 here.. not sure with the squeeling you were referring to though.. anyhow.. i'l build another one, just for the heck of it.. was waiting for the parts and got them now.. i wont rush to finish the build this time.. wish me luck!

[MrStab]

the idea of rebuilding the whole thing kinda bugs me in case it doesn't work again and i waste more parts, but good luck nonetheless.

if i take the plunge, i'll probably use this layout, double-checking with the schem as i go: http://www.sundgist.talktalk.net/Layout/Causality%204/Causality%204%20Phaser%20Stripboard%20Corrected.gif

[jimilee]

does your Regen pot only squeal when you turn it near full clockwise, jimilee?

having relentlessly trawled the web for solutions to various hardware problems for years, it's actually reassuring that quite a few of us seem to have the same problem. this phaser just sounds really, really cool even when it's not working properly!

in certain settings. Phreak over at Byoc suggested removing the shape pit and replacing the speed  pot with a 1mc. I haven't done this yet but that's next. Adding the resistor did kill some squeal and distortion. Checking the solder joints on this thing is tedious as hell, but I found a few bridges ones. That helped also.

[MrStab]

in certain settings. Phreak over at Byoc suggested removing the shape pit and replacing the speed  pot with a 1mc.

thanks for sharing, jimi. amidst all the experiments, i've somehow stopped mine from working altogether (*sigh* typical...) so i'll need to resolve that before i can try myself.

i theorise that either everyone who built the phaser from that layout is having problems but just don't realise it, or we all got it right but think otherwise. lol

or maybe it really is just anally relentless with the parts used. in any case, i just can't see the difference between the TagBoardEffects layout, the other layout i posted and the schematic itself to try and narrow down this problem. damnit! wish i wasn't such a layman. c'mon, you pros! throw us a bone!

[jimilee]

I'm guessing everyone that built this is having issues or figured it out. As I am a solder by numbers type of guy, I have no idea how this solution helps,but he said it helped his.
With etched boards you gotta watch for solder  bridges for sure,they're far to easy to make when working this stuff out.I had an Octavia that I successfully disabled for many months one time trying to work stuff out.

[MrStab]

i'm just using strip/veroboard for this, as my monotony might've suggested. you've just got me thinking - it can't be a problem with just the layout i'm using if you're etching yet we both have the same issue. i'm a bit slow, in case you figured that out already...

what i tried:
-taking out the Shape pot. wasn't sure how to hook up the stray wires, so i tried all combinations. they all still showed a "preference" for one side of the sweep. connecting lugs 1 & 3 made it permanently fast, though.
-put 470k resistor in series with Speed pot just to simulate 1M, didn't really affect the above much.

it's late (7am, i'm clearly the employed sort), but i'm starting to wonder after watching the sample vid again (https://www.youtube.com/watch?v=eqjmauZ7Dao) whether or not there is a problem with my build after all. it just doesn't feel right, it's like i need some weird time signature to play along with it smoothly.

either way, the Regen pot shouldn't squeal at max (it makes some cool police car sounds...) and there shouldn't be thumping when Speed is at max either. so even if i am a moron and the sweep is fine, they remain issues.

[mistahead]

Complete noob thought that may have been presented earlier in a better way... and this was a while ago so memory is sketchy...

I had a series of boost/dirt circuits that shared a common GND rail - it was possible to swing the gain on at least one of the circuits to an extreme and the whole thing would squeal as you've described. I never finished that box up, but I suspected I needed to prevent the resistance reaching zero somewhere along the way to prevent a zero R feedback loop somewhere else in the series.

Thumping sound I've got nothing for (unless its a hybrid circuit and something about it is allowing clock/lfo to bleed into audio path) - but you already knew that could happen and have eliminated that possibility I guess.

[MrStab]

I suspected I needed to prevent the resistance reaching zero somewhere along the way to prevent a zero R feedback loop somewhere else in the series.

hmm... i had pictured a solution based around what you mean, but i've been up all night so i got it all wrong lol. i'll have a ponder when i wake up. i have something similar (albeit minor) with a compressor's release pot squealing on 0 resistance, but i hadn't really connected the two.  thanks for the suggestion, i'll get on that once i get the whole sweep thing sorted (if i even need to...).

i've tried decoupling the whole LFO, but no end to the thumping. maybe it's to do with the (white) LEDs i'm using, can't remember exactly but i think the current rating was on the higher side. it's only at full speed that this happens, which intuitively just seems like the circuit voiding its bowels to keep up.