Phase Evolution!

[Renegadrian]

 

ok I'll try! THX for now...goin' out to see a gary moore tribute band!

[Renegadrian]

NEWS on this one after a week...
It appears (to me at least) that the bias pot is quite useless!!! I got no phasing as I didn't play around with it too much...
It seems to have a sweet pot at about 9/10, either than that I cannot hear any difference turning that pot down or to 10/10.
Also the mix pot is not that great to my ears, yes you can hear some slight differences here, but the deepest depth (sorry) I can have is on 9/10. turning it down cuts it someway and no dramatic phasing on 10/10.
I thank Rick for his layout (still I HATE perf!!! Now more than ever, that was challenging for me!!!) and didn't find it that subtile, but my next one will be a standard one with the univibe mod only (the only addon I find useful!)

And yes, that Gary Moore tribute band has been GREAT!!! Been there with a close friend for a good chat, have a couple of Desperados with that band nailing those classics!!!


EDIT - I was looking at the original unmodified schem and the schem with mods, both by Justin Philpott - I see that the bias part is almost the same, with a 250k trimmer subbed with a 100k pot. But those 2 47k res on lugs 1 and 3 aren't in the original schem - what if I replace those 2 res with jumpers?!

[richon]

Heres is a version of the Phase Evolution with mods on the coupling caps alla Univibe

0.015uF
0.22uF
470pF
0.0047uF


in the video ( http://www.youtube.com/watch?v=kZem8BVMe40  ) i found I have to play more with the trimmer to make it a deeper phasing efect, but sounds pretty awesome with mi KETCHUP Overdrive

[Renegadrian]

My 45 is officially done. It has the standard pot, replaced the bias pot with a 100k trimmer and took away the mix pot.
When the trimmer is in the right position, it has a good depth!!! Not so subtle...
I left the univibe switch, very good mod.

[El Heisenberg]

I'm gunna have to revisit this when i get enough FETs and put in the univibe mods.

The one I built a while back wasn't FET matched and the phasing is unbalanced or something. It sounds best with a distortion before it. Plus this was a while back and the biggest perf project I'd ever done to that point. I went through a big dark and hectic few days trying to figure out what was wrong with it, resoldering joints and checkin a rechecking the schem. I had put the freakinh zener diode in backwards and since it was verticle I guess I couldn't recognize it fast enough. Dammit. Now that I look at it again, If I just had the matched FETs Id do this again no sweat.

[richon]

Heres is a version of the Phase Evolution with mods on the coupling caps alla Univibe
0.015uF
0.22uF
470pF
0.0047uF
in the video ( http://www.youtube.com/watch?v=kZem8BVMe40  ) i found I have to play more with the trimmer to make it a deeper phasing efect, but sounds pretty awesome with mi KETCHUP Overdrive

now  with another mods (taken from some post and thoughts of JC Maillet):  the eight 10K resistors (two for each JFET) where changed for eight 100K resistors:  check the new vibey sound  http://www.youtube.com/watch?v=39iz4tiCmsY

[Pakaloabob]

Hi Rick.
After successfully building your "Little Angel" and "Casuality 4," I'm movin on to the "Phase Evolution."
One quick question: on the schematic for the daughter board you have two 9v inputs to the dual opamp. Should one of those be a ground?

Thanks so much for putting together such great projects! I was originally intimidated by phasers but somehow your circuits have given me confidence that I can build anything if I put my mind to it. 

[frequencycentral]

One quick question: on the schematic for the daughter board you have two 9v inputs to the dual opamp. Should one of those be a ground?

Yes, one should be to ground. My mistake, a copy-and-paste error.

Thanks so much for putting together such great projects! I was originally intimidated by phasers but somehow your circuits have given me confidence that I can build anything if I put my mind to it. 

That's really nice. The P45 is a good place to start. Being so simple everything is clear.

[Pakaloabob]

Ok. Got the regular Phase 45 circuit on the breadboard with the JC Maillet mods and it sounds mighty fine to me 
Haven't added in the extra stages yet, but I will try that tonight if I get time.
Out of 10 FETs, I was able to match a couple of pairs. The ones I used were 1.478v and 1.488v. I have a set of four that are somewhat close: 1.640,1.698, 1.726, and 1.751v. I hope these are matched close enough to use with the 2 added stages. If not, I have ordered a set of four matched ones from Barry.
Anyway, the "vibe caps" are great and I really like the mix option. I like the idea of the bias pot, but I am worried about the functional range. I haven't measured the exact resistance, but the range on my 250k trimpot is verysmall. I think the 100k pot with 2 47k resistors will be more range than I need/want.
I would love to hear what anyone else has used for their bias pot. I will do some experimenting tonight, but it would be nice to know what others have used.

[Pakaloabob]

Just to follow up, here's where I'm at with this project:
I tried out my supposed quad set of FETs with mixed results. As far as I could tell, the ones with Vgs of 1.640 and 1.698 (3.5% difference) did not phase as well as my original ones (<1%). The 1.726 and 1.751 (1.4%) were a better, but I think the original ones were easier to bias.
The GEOFEX article only says "To make matched sets, pick devices that are within a few percent of the same Vgs." It seems from my experience that Vgs matching should ideally  be within 1%, but definitely less than 3%.
When I put together the 2 extra stages on breadboard I got a much deeper effect , as expected. However, the total difference between these four FETs varies up to 6.8%. I believe when I get a properly matched quad set I will be even more impressed.
I tinkered with the bias pot as well, but have not really gotten satisfying results. With the recommended 100k pot and 47k resistors I got most of the useable range in the first 10-20 percent of the pot. Most of the rest of the rotation did nothing. In order to center the bias, I found that a 50k pot with 122k (100k + 22k resistors) on one side and 33k on the other to be pretty close to the feel I was looking for. I did try several other combinations, but this was the closest I could come. Still not very useable in my opinion. My hope was that I could have a small range in the "sweet spot" of the bias and be able to tweak within that range. So far it hasn't worked out and I may decide to omit the bias pot.
The only other thing to consider is the resistor from the speed pot wiper. I think stock is 7k5, but the common mod seems to be 4k1. I am using 4k7 which should still be faster than original, but I am not sure how much of a difference it makes. I don't really care for the super fast speed anyway, except in vibrato mode.
All in all I am very happy with this project. I am glad I decided to go beyond the stock circuit. "Vibe" cap switch is a must and the mix pot is pretty essential as well. If I could figure out how to switch the added stages in and out I might consider that as well so I would still be able to hear the original Phase 45 sound.
In the next couple of days I will probably commit this to a PCB. I already have etched and drilled one from the Tonepad layout. I'll add wires to add the extra stages, maybe using FC's addon board.

[frequencycentral]

There should be a couple of ways to switch between 2 and 4 stages. The easiest would be to tap off the output from an earlier stage, using a switch to select either 2 or 4 stages. here's a schematic to illustrate what a so-called Phase Evolution looks like, including the 2/4 stages switch:

[Pakaloabob]

Brilliant! Much simpler than I thought it would be.
A complete 4 stage schematic, plus the pinout of the dual opamp has been corrected. Nice work FC! You've been such a great help 

[GodSaveMetal]

you will made a layout with PCB please!!!!

[soupbone]

Nice!!

[Pakaloabob]

Last night I started populating the Phase 45 PCB from Tonepad.com. I was looking for places on the board to tap into the LFO and Vref for extra stages - Voila!  In the upper right hand corner there is a large pad where the Vref trace curves around a .01 uf cap. Another large pad to the right of the 3M9 resistor for the LFO. Just drill 2 little holes and wires can be soldered in place.
Since I plan on using the mix pot mod, I have left out the two 10k resistors that lead from pin 7 of the two opamps. Pin 7 of IC2 will have a wire leading from the red dot to the input of the extra stages board. The output of the extra stages board will go to lug 3 of the mix pot. Lug 1 of the mix pot will go to the green dot, and lug 2 the yelllow dot.
In order to insert a switch to select 2/4 stages, lug 3 of the mix pot would be connected to the center of a SPDT toggle switch instead of the output of the 4th stage. The outer 2 lugs of the switch will be attached to the output of stage 2 or stage 4.
I didn't get a chance to try this out yet so it is NOT VERIFIED. I won't have time to try it out until saturday.

[deadastronaut]

@bob, i built this version of the phase 45, i made sure i matched the fets etc..but it is very very weak on actual phasing...
i tried various trannies but its still weak..

any ideas on this?..

i ended up building the ggg version...with no problems... an phases great.

but i would like to get this one going too...rob.

[Pakaloabob]

I finally got my Tonepad Phase 45 PCB circuit working. I had a little bit of troubleshooting because of a sketchy trace between the speed pot and 4k7 resistor (7k5 stock).
I am happy to report that the wiring from my diagram works as planned for adding extra stages.
I am in the process of designing a perfboard layout for the extra stages plus spots for the stock/vibe caps and the 2/4 stages switch.

@Rob H.
I wasn't sure if you meant this version, as in the tonepad PCB or FC's phase evolution perf layout.
I myself am very new to building phasers. My only other experience was Causality 4 (great circuit  ).
If you built the GGG Phase 45 successfully, I guess you know what it is supposed to sound like and that it is not an in-your-face type of effect.
Did you use the same kind of FETs for both versions? I have read that some FETs do not work as well as the Fairchild 2N5952 that I used. I also found that I had to match the FETs very closely to get a good efffect. I believe that even a 3 percent difference will make it hard to dial in the bias properly. Did you try swapping the FETs you matched from one version to the other?
I also think the pinout for the FETs and the ICs are reversed between Tonepad and GGG versions. You'll see the notches of the ICs are together in the Tonepad PCB, but at opposite ends in the GGG version
I find the bias range is a bit touchy, but again, if you have built one version of the Phase 45 circuit you will know that.
By the way, did you do any of the mods? I really like the vibe caps and mix pot. The extra stages really spices up the phasing too.

[deadastronaut]

I finally got my Tonepad Phase 45 PCB circuit working. I had a little bit of troubleshooting because of a sketchy trace between the speed pot and 4k7 resistor (7k5 stock).
I am happy to report that the wiring from my diagram works as planned for adding extra stages.
I am in the process of designing a perfboard layout for the extra stages plus spots for the stock/vibe caps and the 2/4 stages switch.

@Rob H.
I wasn't sure if you meant this version, as in the tonepad PCB or FC's phase evolution perf layout.
I myself am very new to building phasers. My only other experience was Causality 4 (great circuit  ).
If you built the GGG Phase 45 successfully, I guess you know what it is supposed to sound like and that it is not an in-your-face type of effect.
Did you use the same kind of FETs for both versions? I have read that some FETs do not work as well as the Fairchild 2N5952 that I used. I also found that I had to match the FETs very closely to get a good efffect. I believe that even a 3 percent difference will make it hard to dial in the bias properly. Did you try swapping the FETs you matched from one version to the other?
I also think the pinout for the FETs and the ICs are reversed between Tonepad and GGG versions. You'll see the notches of the ICs are together in the Tonepad PCB, but at opposite ends in the GGG version
I find the bias range is a bit touchy, but again, if you have built one version of the Phase 45 circuit you will know that.
By the way, did you do any of the mods? I really like the vibe caps and mix pot. The extra stages really spices up the phasing too.

yep i meant the one above, not ricks one (which always sound superb).
it is very weak indeed, i sold my other one so i couldnt nick the fets out to try it..
i wasnt after a deep phase anyway,but just a bit more than this has...
but i may have to bite the bullet and build a proper kick ass  rick phaser...and be done with it.  cheers rob.

[Pakaloabob]

When working on my breadboard build I used JC Maillet's schematic and Rick's layout which have the Source going to Vref. I then noticed that the Tonepad layout has the Drain of the FETs going to Vref. Is this possible because the FETs are acting as variable resistance elements controlled by the Gate voltage?

[frequencycentral]

When working on my breadboard build I used JC Maillet's schematic and Rick's layout which have the Source going to Vref. I then noticed that the Tonepad layout has the Drain of the FETs going to Vref. Is this possible because the FETs are acting as variable resistance elements controlled by the Gate voltage?

Source and Drain are interchangeable in most applications (if I have my facts right), I don't think it would be that. You are correct that the FETs are acting as variable resistance elements controlled by the Gate voltage.

As I said in the first post of this thread:

After buiding and testing the main board I wasn't really happy with the quite subtle phasing.

....that was before I added the extra stages. TBH I can't remember back to exactly what it sounded like, it just wasn't what I was after. You got me thinking now maybe there's an error in my original layout - now I'll have to check it again to be sure. But then again, my FET's were not matched as closely as you're saying they need to be, so maybe it was that. Either way, I still adore my Phase Evolution, despite it sitting right next to my Sonic Death Ray.


EDIT: Another thing to try (which I didn't) with the 4 stage version is a Phase-90-Block-type fixed regen resistor. If you compare the above with a Phase 90 Block schematic, you'll easily see where to add it. As is, the 4 stage Phase Evolution is more akin to a Phase 90 Script but with less distortion, courtesy of the improved circuitry around the FETs.