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

[norv]

Hi,
In 2015 I built a stripboard version of the Causality 4 Mk II using tagboardeffects layout here http://tagboardeffects.blogspot.com/2012/02/causality-4-mkii-rick-holt.html .
It suffered from very low output and I got busy on other stuff.

I just revisited it and discovered that if I touch anything metal (screwdriver, tweezers etc.) to pin 12 of the IC2 TL074 (or TL084) the output becomes much louder, ie. "normal". Everything else seems to work. I tried a TL074 and a TL084 with the same result.

Can anyone suggest what to do next? TIA 

[norv]

FWIW I rebuilt the stripboard and now my phaser works. 

[bluebunny]

Good news.  I'm guessing from your "touch-it-and-it-works" description that you may have had a dry joint?

[norv]

Yes that's  the most likely possibility. The original build was pretty dodgy, using two scraps of stripboard "joined" with tiewire.. definitely sub-optimal 

[snk]

Hello,
I am building the Causality 4 Phaser MkII from this veroboard layout. Everything is going well so far, except that i just noticed that the 10nF capacitor is display in yellow, like a ceramic capacitor.
I have polyester and mylar 10nF caps, but no ceramics : is it important to use a ceramic cap, or can I just use any kind of capacitor, as long as it is 10nF?
Thank you !

[Edit] I checked TonePad layout, and the cap is the same than the other, so i think i have found my answer

[bluebunny]

I think it was probably shown in that layout as a ceramic since it needs a 2.5mm pitch in that position.  But anything you have to hand will do: it's in the LFO, not audio.

[Mark Hammer]

And besides, it's rock and roll, where cap quality doesn't often make any audible difference.  If it was an analog synth VCO, where stability and precision mattered more, THEN you'd be right to ask about type.  But for this particular circuit, rest easy.

[snk]

Hi, Thank you.

I just finished the build : So far, it sounds great ! I love phasers, and this one is very versatile with a sound on its own and many options. It's great it can do slow sweeps, and it sounds quite "synthy".

However, something is wrong, because I get a weak sound (low volume, no bass), and the phaser goes wildly into self-oscillation (I don't mean the expected self oscillation when the regen is cranked).

I have used 13700, TL074, 5532, as advised, but i have read that Rick Holt had used TL084 : could it be that? I am still reading the thread, but there are 26 pages(!), and haven't found a mention about such an issue yet... I am also obviously double-checking my build, but would such symptoms sound familiar to you (low volume, cranked resonance)?

[snk]

... and this is the kind of thing to expect when you forget to solder one chip socket's pin 

After close inspection (and one soldering on the missing pin), everything works as expected now, and I like this phaser a lot : thank you Rick/Frequency Central !

[bluebunny]

Result! 

If you like the C4, you might also enjoy the C6. 

[snk]

Ah ah !
For now, I think 4 stages will be enough. I often like softer phasers (2 stages), and 4 stages is creamy enough to my needs most of the times.
... But now that i know how great Causality4 sounds, who knows, I might be tempted at some point

[KarenColumbo]

Aaaaaand another one. Just breaded it, love this thing. Will try with the new TapLFO during the next days. Looking to somehow incorporate the Vibe/Whirl/Swirl trick from Tri-Vibe (ROG), though, instead of the "regen" pot. Maybe put it from buffer output pin to output pin of the last phase shifter.

[pinkjimiphoton]

holy cow, the whole enchilada!
i sent mine to steve hunter over in espana, so i need to rebuild myself another.

there's also a brilliant verified layout(s) on tagboard effects for this, with some other mods.

[KarenColumbo]

holy cow, the whole enchilada!
i sent mine to steve hunter over in espana, so i need to rebuild myself another.

there's also a brilliant verified layout(s) on tagboard effects for this, with some other mods.

Good one, will have a look. I have the ambition to make all my PCBs myself - got the photo positive etching stuff, maybe it's time I tried a double sided one for once. Heh, this will be a hectic thing between expose top and bottom side and quite a sprint to the developer bath

[KarenColumbo]

Just added the "Width" pot from Mk. II to my Mk. I Causality 4 bread. Now the sweep is much stronger than before. Nice!
I see that probably the biggest difference between Causality and Tri-Vibe is that the former doesn't utilize the LM13700's "Diode Bias" pins (2 and 15). "Instead" there's this 1k8 resistance 'tween the internal diff amps positive and negative inputs. If I now go and connect the diode pins to V+ with some resistance in series AND rip out the resistor between pos. and neg- op-amp inputs and put them to Vref via small resistors (470R @ Tri-Vibe), what will happen from a theoretical point of view? Since the LFO's output connects to pins 1 and 16, which are "Bias Inputs" AND the pos. and neg. amp's input are connected to V+, Diode Bias connected to Vref halfway between V+ and GND, what does that mean for effectivity?

[garcho]

AND the pos. and neg. amp's input are connected to V+

V+ or Vref?

Since the LFO's output connects to pins 1 and 16, which are "Bias Inputs"

I think I'm misunderstanding you, but in case I'm not, those pins, 1 and 16, "I_ABC", though labeled "bias" are the voltage/current control pins, they don't have anything to do with biasing inputs so AC can ride on DC, like what we do for single supply designs in guitar pedal world.

[PRR]

> ...those pins, 1 and 16, "IABC", though labeled "bias" are the voltage/current control pins, they don't have anything to do with biasing inputs so AC can ride on DC, like what we do for single supply designs in guitar pedal world.

Iabc really does set the idle current, a traditional function of "bias".

As you say it does not affect the in and out DC voltages, so it is unlike most of our usual circuits.

[FingerBlisters]

Long time no post.

Is there a schematic with designators anywhere for this? The OP mentions R5, C7 etc throughout this post but the schematic only has values so it's impossible to know which is which.

Any leads after all this time?

EDIT: also, pot lug numbers should be mandatory on all schematics. I have a chronic fear some of my pots will be backwards.

[bluebunny]

I presume those designators refer to Rick's PCB/perf layout.  Without looking back over the thread, I'm guessing they may have disappeared...

Edit: Take a look at page 2.

Edit #2: Take a look at page 23.  A while back I re-posted all the schematics and layouts from this thread that I have in my stash.

[FootSolder]

Is anyone offering a pcb for the mkII? It seemed like GuitarPCB did for a while but my query never got a response. Maybe someone on the forum can do single order fabs?