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

[in3x0rable]

What values are you using for R10 and R12?

I believe 10k. I built it to the specs of Revision 1.3.

[frequencycentral]

What values are you using for R10 and R12?

I believe 10k. I built it to the specs of Revision 1.3.

Neither R10 or R12 are 10k, they are 68k and 47k respectively. What layout are you using?

OK, anyway, you built a MkI from the schematic on page 1 of this thread. Change the 100k resistor (that goes from the -ve input of the output stage to ground) for a 47k. That's R12 on the perf/PCB layout. This was corrected in MkII.

[in3x0rable]

http://www.sundgist.talktalk.net/Layout/Causality%204/Causality%204%20Phaser%20Stripboard%20Corrected.gif

Actually, I built it from that diagram if it changes anything. But I see which resistor I need to change. Thank you very much.

I was assuming that the 68k resistor controlled the output volume?

[frequencycentral]

Here's my new MkII:

[doc_drop]

Rick,

That is a flippin' beautiful build! Are you liking the improvements we worked on? Have you tried it out in rehearsals yet?

Mine sounds great, but it sure doesn't look as beautiful as that!

[frequencycentral]

Hey Chris, just finished it today and had an hour to play with it before Mrs FC demended 'my immediate attention'......... The extra controls are really useful, particularly the width pot. I socketted R5 and R33 as I want to experiment with those two values, currently I've got 22k and 220k respectively (you used 10k and 330k), I'll try your values though, as the LFO isn't quite symettrical in the mid position of the shape pot. I'm also going to change the speed pot from 470k to 1M to go slower. You might notice I added a trimmer in place of R12, as I really wanted to get the volume perfect.

[jacobyjd]

Hey Chris, just finished it today and had an hour to play with it before Mrs FC demended 'my immediate attention'......... The extra controls are really useful, particularly the width pot. I socketted R5 and R33 as I want to experiment with those two values, currently I've got 22k and 220k respectively (you used 10k and 330k), I'll try your values though, as the LFO isn't quite symettrical in the mid position of the shape pot. I'm also going to change the speed pot from 470k to 1M to go slower. You might notice I added a trimmer in place of R12, as I really wanted to get the volume perfect.

You used entirely too many periods there...

[frequencycentral]

Hey Chris, just finished it today and had an hour to play with it before Mrs FC demended 'my immediate attention'......... The extra controls are really useful, particularly the width pot. I socketted R5 and R33 as I want to experiment with those two values, currently I've got 22k and 220k respectively (you used 10k and 330k), I'll try your values though, as the LFO isn't quite symettrical in the mid position of the shape pot. I'm also going to change the speed pot from 470k to 1M to go slower. You might notice I added a trimmer in place of R12, as I really wanted to get the volume perfect.

You used entirely too many periods there...

I can assure you the number of periods used was entirely appropriate......... 

[sundgist]

Here's my new MkII:

Very nice.
Would the empty half of the enclosure be intentional? Extra stages with Mark Hammers phase filter?

Mine is still out on the work bench. Havn't had the time to put it in a box yet, or try out adding the extra stages.

[frequencycentral]

Would the empty half of the enclosure be intentional? Extra stages with Mark Hammers phase filter?

It does look that way doesn't it? Though it wasn't the intention, it was just the best way to mount the board.......but now you mention it, I have left my options open haven't I?!

[frequencycentral]

After playing about with my MkII I've done the following tweaks to get it how I like it:

• R5 = 220K
• C4 = 47uF

R5 at 220k appears to me to keep the LFO symettry. I increased the value of C4 (the timing cap) because the addition of the shape control has the effect of approximately doubling the minumum available speed. I like very slow phase sweeps, so I played around with paralleling different value caps with the existing C4, I really liked the sweep with a 33uF in parallel, so I'm going to sub a 47uF for the existing 10uF. The fastest speed is now slower though, so it's a trade off.

[sundgist]

Managed to get some time to work on this again, trying to cram it into an enclosure and leave a bit of space for the extra board.

Noted a few fixes on my layout while looking at a few things on the o-scope. Layout has been updated.

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. Also noticed the lfo is getting clipped as the width control goes past halfway. Making this 10k resistor larger limits the gain and stops the flats at the top and bottom of the lfo. I've switched mine to 47k. Saying that, adding more gain here gets the lfo looking more square which can give some interesting effects.

[solfin]

I have a question about the wax and wane LEDs. I dont fully understand the schematic.

What does the top arrow connect to?

I'd also like to thank everyone who worked on getting this build to where its at and providing the layouts. Can't wait to get this running.

[frequencycentral]

What does the top arrow connect to?

The top arrow indicates the +ve voltage connection, ie 9 volts.

[Spidermonkey]

Oh! So you have another wire connecting Range 3 to the board?

[solfin]

What does the top arrow connect to?

The top arrow indicates the +ve voltage connection, ie 9 volts.

I did do a quick search for circuit diagram symbols and couldn't find an arrow used like that. Thanks for explaining.

[stringsthings]

The go-to phaser builds for DIY'ers are:

Phase 45 – Intermediate build. 2 stages. FET matching required. No regen. Very subtle.
Phase 90 – Advanced build. 4 stages. FET matching required.
Ross Ropez – Advanced build. 4 stages. OTA design.
Small Stone – Advanced build. 4 stages. OTA design.

The design concept for "Causality 4" was to achieve a musically useful intermediate build 4 stage phaser with regen, using easily available parts, and requiring no matching of components. It has two swept stages using a dual OTA, and two fixed stages using opamps. The LFO utilises a dual opamp and is based on the MXR phasers, much simpler than the LFOs in either the Small Stone or Ross Ropez. The fixed stages came from an idea suggested by Mark Hammer in this thread: http://www.diystompboxes.com/smfforum/index.php?topic=80111.0 Having four stages, even if two are fixed, allows for the addition of regen, which for me is a phaser essential. The Regen control goes from zero to just short of self oscillation - some great sounds available here. The Depth control is particularly interesting and useful, specifying where in the spectrum the phasing occurs.

Your critiques are welcome!

Soundclips, perf and PCB layouts to follow .....

this thread is just cooler than cool can be !  .... i'm putting this project on my "must-build-in-the-future" list .... pardon me while i go source some chips !! 

[jacobyjd]

Ok--After adding one forgotten jumper, I finally got my C4 up and running. It sounds pretty good, despite the fact that I wired all the pots backward 

However, the one major issue it does have is that the output with the effect on is WAY low. Any ideas on what could be causing this? I haven't taken any voltages yet, because I finished it just before bed last night. However, given that it functions perfectly all around except for the output volume, i'm thinking it might just need a couple resistor swaps.

Does that sound right?

I'm hoping to get back to it tomorrow evening, so I should have more info then.

[frequencycentral]

Hey Josh, glad you got it up and running. The volume issue is something I (attempted to) addressed in the MkII. The volume is set by by R10 and R12 in combination (on the perf/PCB layout), the closer those two values are to each other the lower the volume. R10 should be a larger value than R12. On my MkII build I ended up using a 100k resistor for R10 and a 100k trimmer instead of R12 so I could adjust to unity without having to dink around with socketting resistors. How come all your pots are backwards? I did label them correctly right?

Other mods I made to my MkII:

• R5 = 220k
• C4 = 47uF (I just paralleled a 33uF with the existing 10uF)
• R33 = 47k

[jacobyjd]

The volume is set by by R10 and R12 in combination (on the perf/PCB layout), the closer those two values are to each other the lower the volume. R10 should be a larger value than R12. On my MkII build I ended up using a 100k resistor for R10 and a 100k trimmer instead of R12 so I could adjust to unity without having to dink around with socketting resistors.

Fantastic--that's where I was thinking of looking first. You explain it in very practical terms. I'll fiddle around a bit when I get some time to dig into it again.

How come all your pots are backwards? I did label them correctly right?

lol..yeah...I built the vero, and looking at the schematic, I can never tell which lug is which. Usually I orient myself to the layout by a volume control voltage divider pot at the output. Since there's not one here, I was counting on the 50/50 chance to fall in my favor  Not so much this time

However, it's all pretty tightly wired. I'll probably re-do it all anyway, given the resistor swaps I'll need to do.