I've done this layout, took a while, designed to fit into a Hammond enclosure (can't remember it's code) 4.7" L x 3.7" W x 1.34" H. (120mm x 95mm x 35mm). The layout is designed for the enclosure to be 'landscape' as opposed to portrait'. I used LM324 quad opamps to keep the size down. A 5 knob build. I know the chances are very slight - but anyone care to check it over for any obvious errors before I start building it? Thanks!
(http://i210.photobucket.com/albums/bb292/frequencycentral/180Layout.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/180LayoutReveal.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/p180plus.gif)
Link to GEOFEX article: http://www.geofex.com/FX_images/p180plus.gif
Here's the PCB version and PNP just for the hell of it, still needs to be verified though:
(http://i210.photobucket.com/albums/bb292/frequencycentral/180PCBLayout.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/180PNPLayout.gif)
Make sure and buy 20 bazillion fets to match!
Quote from: nelson on May 28, 2009, 11:08:00 AM
Make sure and buy 20 bazillion fets to match!
Wot? Won't 8 be enough then? :icon_mrgreen:
Just thinking out loud - I haven't got enough 0.047uf caps in stock to make this ATM, though I do have 20 bazillion 0.1uf. I'm just wondering how much difference it will make?
Hi,
I'm working on something pretty much like this and I just want to say that you could add a second trimmer to adjust the bias of the second 4 transistors to avoid the matching, maybe it could give you more possibilities to get nice and deep phase.
Let me know ;)
Greetings.
Quote from: Slade on May 29, 2009, 11:31:49 PM
Hi,
I'm working on something pretty much like this and I just want to say that you could add a second trimmer to adjust the bias of the second 4 transistors to avoid the matching, maybe it could give you more possibilities to get nice and deep phase.
Let me know ;)
Greetings.
Hi, nice idea, but I'm planning for the bias to be a panel mounted pot, as interesting variations are available. I've got a bunch of 2n5485, and I'm using sockets in my build for the FETs, so if the batch I have don't match up I'll just have to get some more! At least with the sockets I'll be up and running, just not quite there
Just a quick note, I did this layout using LM324 quad opamp packages for two reasons, one to save some space, and two because I have a bunch of LM324's that need using. TL064's and TL084's have the same pinout as LM324's so they are options too!
That's fine ;)
I don't really think that a external control for the BIAS could be very useful, let me know if it's so or not, please.
I'm doing mine using NE5532 Opamps, they're really clean and nice sounding, have you tried them?
Quote from: Slade on May 30, 2009, 01:16:03 PM
That's fine ;)
I don't really think that a external control for the BIAS could be very useful, let me know if it's so or not, please.
I'm doing mine using NE5532 Opamps, they're really clean and nice sounding, have you tried them?
There's an external bias on my Phase Evolution: Phase 45 with JC Malliet's mods (http://www.diystompboxes.com/smfforum/index.php?topic=76657.0), to which I added two extra stages. The bias control does add some extra interesting flavours.
Yup, I've got some NE5532, but I've got a glut of LM324 which I'm trying to deplete!
Excellent, excellent..
Finally, what would be the function of the Regen control in this phaser? Can´t find it looking at the schematic, is it the 47k pot (I thought this is a trimmer) before the mix pot?
Quote from: Slade on May 30, 2009, 01:56:42 PM
Excellent, excellent..
Finally, what would be the function of the Regen control in this phaser? Can´t find it looking at the schematic, is it the 47k pot (I thought this is a trimmer) before the mix pot?
The Regen is a resonance control, or a feedback control. It feeds the output back into the circuit and accentuates the notch frequencies. It can sound very filtery and chewy.
Ok, so that is what I'm doing by replacing the 22k (common mod) for a 100k pot in series with a 15k resistor. I'm not doing the Mix mod, but I'm doing a "Depth" control by changing the 1M resistor to the BIAS for a 620k resistor in series with a 1M pot, by increasing the value of this resistor you lose depth of the phaser and get a change in the tone and by decreasing it you get more deep phase sound, I think you should try it, it works perfect and gives you pretty nice textures ;)
Greetings.
Quote from: Slade on May 30, 2009, 02:05:48 PM
I'm doing a "Depth" control by changing the 1M resistor to the BIAS for a 620k resistor in series with a 1M pot, by increasing the value of this resistor you lose depth of the phaser and get a change in the tone and by decreasing it you get more deep phase sound, I think you should try it, it works perfect and gives you pretty nice textures ;)
Greetings.
Yes, I think that is referred to as 'Width' in R.G.'s schematic. Mark Hammer had suggested a resistor in series with the 1M pot, I was going to have to experiment with that, so thank you for confirming it, I'll do it your way!
Perf populated, now I'm waiting for the FETs to arrive, that's what the four six pin SIL sockets are for. I decided to use a BC212 PNP instead of the BC557 I listed on my layouts, as it's hfe is very close to the 2n4125 used in the original P90.
I think this is the best perf work that I've ever done:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0004-5.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0005-5.jpg)
:icon_eek: :icon_exclaim: :P
Master Perfer :o
it makes me dizzy just looking at it. well done, know make me one...
Just finished testing my build. I can confirm that the perf layout is now officially VERIFIED! Cool! Therefore, the PCB layout should also be verified, as all I did to that was copy the perf layout and replace the jumpers with traces. I can also confirm that this circuit works well with LM324, which I did have some misgivings about due to their preference for single supply rail operation, but they work just fine.
I ordered and tested thirty 2n5489 FETs, and was lucky enough to find three pretty well matched sets, with Vgs of ~1.8v, ~2.3v and ~2.5v. Having said that, I also tried some unmatched 2n5457 left over from my four stage P45 build, and it still sounded pretty good once the bias was tweaked in.
I still have to do some tweaking of the range of the Bias and Width pots. For the Bias I used a 100K pot with a 47K resistor in series at either end, I need to remove the resistor between the pot and ground, and increase the other end to 100k to put the centre bias central on the pot. I also need to reduce the 430K resistor I put in series between the Bias pot and the Width pot.
If anyone wants them, I've got two spare well matched sets of eight 2n5489, or four sets of four if you just want to build a 4 stage stock phase 90. PM me.
Here's my circuit board with the pots mounted on a seperate piece of perf, makes it very easy to test/mod:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-7.jpg)
Here's the pot board layout too, it may help to explain the resistor values I'm changing to get the Bias pot and the Width pot working right:
(http://i210.photobucket.com/albums/bb292/frequencycentral/180pots.gif)
After playing about with the resistors I placed either side of the Bias pot, I'm coming to the conclusion that I should maybe change out the 5.1v zener for a higher voltage zener, as the 'centre' bias is still pretty close to ground. The Tonepad P90 project file mentions something about this for subbing in different types of FETs. The matched set I'm using has a Vgs of 1.8v, I suspect that lower than this would be easier to bias with the 5.1v zener. My vref is ~3v at the moment, I'm wondering if I use a different zener to get the vref up to ~5v I'll get the centre bias close to the centre of the Bias pot. The alternative is increasing the value of R3 on my pot board (I've already reduced R2 to 0K), but it seems to be a diminishing returns situation. Any thoughts anyone? It would be great if R.G. could chip in here.
I searched and found a P45 (with univibe mods) thread where JC Maillet suggested putting one or two 1n4148 in series with the zener to raise the vref and centralise the bias on the Bias pot, so I'll try that.
All done!
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002-8.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0001-20.jpg)
Great work Rick!
The board looks very nice. Cleanl
Curious to hear how it sounds.
john
Thanks John, the board took quite a bit of planning. My favourite part is how the board is secured inside the enclosure (and grounded/powered) using solid core to the in/out sockets and the DC socket. I dislike having boards loose inside enclosures, so this was a good solution for me. I'll be doing it that way again.
As for how it sounds, I've never owned or built a Phase 90 to compare it to, though last month I built a Phase 45 to which I added two extra stages. The P180 is definately a thicker phase, though I'm not finding it as 'intrusive' as say a Small Stone with the color switch on, or my old Boss PH2 in mode II, which may be a good thing as the phasing it offers is musical without being over the top. I'm also not entirely convinced of the value of the extra pots really, I need to play with it a lot more though to discover all the possibilities, but there seems to be a sweet spot for each. But I'm on a phaser quest, so it was worth building. Still searching for the ultimate swooshy phaser, next up will be an eight stage Ross with the Hammer mods. I tend to use some of my pedals for gigging/rehearsal, some set up in my home guitar rig, and some set up with my Rhodes 73 MkI, so I have no problem in duplicating pedals!
Didn't you get some phase oscillation noise when you're not playing or volume loss with the 8 stages version?
I made this (not uising your layout, but one I made) and it works but I have that 2 problems.
I'm using NE5532's for the LFO and I used different cap values for the first two and last two stages and the 4 stages between them in this order: 33n/33n - 47n/47n/47n/47n - 33n/33n.
I made this 8 stages selectables with a toggle switch, so you can have 4 or 8 stages.
I can hear the oscillation of the paser when I'm not playing... :-\
I don't have any volume loss - maybe you need to look at the output transistor and its associated resistors. Not sure what you mean by phase oscillation noise, but yes I can still hear it quietly doing it's thing when I'm not playing.
I have different issues. My vref is 4.1 volts, so the central point of the bias pot is a little off from where I'd like it to be. I'm going to see if I can get the vref down to ~3 volts, which should solve the problem, though I suspect it's linked to the Vgs of the FETs I'm using.
The Regen/Feedback control doesn't seem to do anything at all, I'm going to try feeding it back at different stages to see if I can get it to do anything. The only post I can find about a Phase 180 build also states that this pot doesn't do anything.
Also I used a 100K Mix/Blend pot, though the schematic states 200K. I don't think it should make any difference, but it doesn't work in quite the same way as the similar pot on my JC Mailett modded Phase 45.
It does sound great though!
Thakns for your inspiration :D Now I know what's is causing the volume drop..
Yes, with phase oscillation noise I was saying that I can still hear the pedal doing his work when I'm not playing.
Well, my regen pot is woking fine, I'm "feedbacking" to the second stage, not the first, with a 27K resistor and a 50k pot. I didn't use the mix pot, instead of it I use the Width (or depth) pot, like I said before in this thread, and it works great.
Regards.
Rick,
I had a go at building your (spin-off) layout for the Phase 90 and I've had quite a nightmare trying to get it to work. After some hours of checking and double checking I'm pretty sure I see a mistake in your layout.
According to the schematic, the output of each opamp should connect directly to the 47n cap for the input of the next stage and not through a 10K resistor as you've done with your layout. That said, I'm sort of baffled as to how you've got your Phase 180 working because you have exactly the same layout "mistake"... if I'm right that this is a mistake, that is.
I am in disbelief as to the that perfboarding... How did you make it so perfect? You should make a video tutorial or something so we can all try to be 1/10th as good! At least I'd love to see a video like that. I probably couldn't perfboard an SHO booster circuit. :/ Well actually I tried and failed at perfboarding a rangemaster and that's a pretty darn simple circuit.
QuoteYou should make a video tutorial or something so we can all try to be 1/10th as good! At least I'd love to see a video like that.
+ a gazillion.
Quote from: GP on June 25, 2009, 01:05:44 PM
Rick,
I had a go at building your (spin-off) layout for the Phase 90 and I've had quite a nightmare trying to get it to work. After some hours of checking and double checking I'm pretty sure I see a mistake in your layout.
According to the schematic, the output of each opamp should connect directly to the 47n cap for the input of the next stage and not through a 10K resistor as you've done with your layout. That said, I'm sort of baffled as to how you've got your Phase 180 working because you have exactly the same layout "mistake"... if I'm right that this is a mistake, that is.
Damn, you are correct. I've ballsed it up. Mine does phase, though I have a problem which I assumed was to do with the FET biasing, but you've just pointed out that I've made an error with the layout. Oops, and sorry. Having said that, it should be pretty easy to correct. Thank you for pointing it out, I'll correct my build and update the layouts over the weekend. :icon_redface:
Quote from: doitle on June 25, 2009, 01:56:20 PM
I am in disbelief as to the that perfboarding... How did you make it so perfect? You should make a video tutorial or something so we can all try to be 1/10th as good! At least I'd love to see a video like that. I probably couldn't perfboard an SHO booster circuit. :/ Well actually I tried and failed at perfboarding a rangemaster and that's a pretty darn simple circuit.
Thanks - but I still make dumb mistakes! Oh well. Perfect perfing? Use a pointy fine tipped soldering iron, use thin solder and be frugal with it, follow a good layout (hah!), take your time. A video tutorial? Well maybe I could do that sometime, let me think about it. It's actually very flatteing to be asked for one!
Well, i'm even more baffled then because that (very very beautiful) soldered perfboard picture you posted looked just like your layout. As an aside, your regen return is injected into the wrong place too! I noticed you'd posted that it didn't seem to do anything on your build - this might be why!
As per the Phase 90 layout you posted, mine wasn't phasing but behaving like a tremolo - are you sure yours IS phasing and not just having more of a pronounced effect than mine because of more stages?
Anyway, I made some adjustments to mine to fix the problem. It's not as easy as one would like because i had to route some wires under the board because your layout is so tight. It's working better but it's still not working as a phaser so maybe i've missed something else. Everytime I connect in the regen, it squeals like a pig so I still need to work on it.
Quote from: GP on June 25, 2009, 02:28:25 PM
As an aside, your regen return is injected into the wrong place too! I noticed you'd posted that it didn't seem to do anything on your build - this might be why!
Yeah, I'd noticed that and corrected it to the right place already, still no control over regen though, which is obviously to do with the mistake (x8) you've pointed out.
Quote from: GP on June 25, 2009, 02:28:25 PM
.....are you sure yours IS phasing and not just having more of a pronounced effect than mine because of more stages?
Mine is phasing, but with issues as I said. Maybe you are right that the extra stages make it more pronounced with mine.
You've actually got me really stoked to get this sorted, with mine it's like there's a really good effect in there just waiting to get out. I assumed all the issues were FET biasing based, but obviously not!
As for your other issues, maybe they are FET biasing based. See this thread: http://www.diystompboxes.com/smfforum/index.php?topic=77324.0
I can't thank you enough for bringing this to my attention, now I know there's a major flaw I just can't wait to get it 100%!
Quote from: frequencycentral on May 28, 2009, 09:20:24 AM
I've done this layout, took a while...................I know the chances are very slight - but anyone care to check it over for any obvious errors before I start building it?
Well, where were you then? :icon_biggrin:
where was i then? somewhere in france on my way back to the uk... no internet, no soldering iron, no help at all, i'm afraid.
I only built this because i've had some matched Jfets lying around for ages and i've just not gotten round to it. I'm currently collecting together parts to build a Tau Pipe phaser (not for guitar use) so I thought i'd get myself into the moodfor phasers while i wait. I'm normally a vero man but your layout looked lovely so i didn't even think to verify it before putting solder to board.
yes, i'm figuring the the problem is fet biasing but it's taken me long enough to realise the problem with the layout!
Quote from: GP on June 25, 2009, 02:53:51 PM
where was i then? somewhere in france on my way back to the uk... no internet, no soldering iron, no help at all, i'm afraid.
Shame on you!
The Tau is a serious project - nice! I love phasers, I'm on a phaser quest myself, I've tried and failed to design a submini tube phaser, though it shouldn't be so different from the submini tube vibrato I've previously posted, so I figured I'd go phaser crazy to get me prepared for the next stab at the tube phaser. I'll do an 8 stage Ross soon too. My previous phaser build, a P45 with 2 extra stages and JC Maillet's mods went so smoothly. Ah well, we all gotta @#$% up sometimes............
Yep... the tau is serious but i have a spare 19" rack box and it needs filling with something interesting. A 9v stompbox phaser doesn't really cut the mustard in that setting.
i'm not so worried about knocking up a tau on vero as much as trying to get hold of the parts. Not easy to find 3046s nowadays and lm394s or ssm2210s are not cheap if you've got to buy 22 of 'em.
So I've just performed the surgery required to correct my layout @#$% up. Wow! The 'really good effect in there just waiting to get out' has now been unleashed! Amazing, a very deep and chewy phaser. The Regen control and the Blend control have now totally come to life. The Regen self oscillates when it's maxed out, so I'm going to add a larger value resistor to set the maximum a little lower. The surgery wasn't fun, entailing making 7 little 'bridges' from one point to another. I'm not sure if it's going to be easy to amend the layout to take in the corrections without adding slightly to the board size. I'll have a crack at it anyway.
The corrections I made are within the areas inside the black circles, entailing cutting a jumper and inserting a short red wire in each case, except for one that just required a jumper to be moved. If you compare it to my original layout you'll get the picture. The Regen connection has now been moved to the correct location.
(http://i210.photobucket.com/albums/bb292/frequencycentral/Corrections.jpg)
Thanks again to GP for pointing this out and helping me make this build work the way it should.
Any chance of some samples ?? I was gonna build a plain old phase 45, but I think I'm about to change my mind ;)
Also, do all 8 FET's have to be matched ?? I can get hold of matched FET's in batches of 4, not 8.
I'll try to get around to soundclips over the weekend. I also need to revise the PCB slightly in light of my errors. :icon_redface:
Yes you do really need all eight FETs to be matched. The set I used have a Vgs of -1.8 volts. I'm still in the dark as to the optimal Vgs for FETs in Phase 90 and derivatives, though my instinct tell me that maybe -1 volt to -1.5 volts would be good.
I used LM324 quad opamps because I have loads, TL084 (for example) have the same pinout and should would just fine too.
At the risk of impeding an in-progress party, ( :icon_biggrin: ) I've had good luck retrofitting the phase 45 style JFET gate-drain feedback circuit into P90 phasers. It cuts the JFET distortion a lot, making it sound much smoother.
I don't want to be pushy, but has the PCB been revised yet ?? I'm new to making PCB's and I don't have the confidence to run with it myself !! I've also managed to get myself 8 matched 2N5952's which has helped to treble my excitement/impatience.
Thanks.
Quote from: 1878 on July 16, 2009, 03:21:33 PM
I don't want to be pushy, but has the PCB been revised yet ?? I'm new to making PCB's and I don't have the confidence to run with it myself !! I've also managed to get myself 8 matched 2N5952's which has helped to treble my excitement/impatience.
Thanks.
I haven't got round to it yet, I'll try to find time over the weekend, though I'm off abroad on Monday, so it's going to be a busy weekend preparing. I'll try to make time for a fellow scouser even if you do support the wrong team. :icon_biggrin:
Ooohh... I suppose I'll have to take that one on the chin ;)
Here's the revised PCB and PNP, which i now believe to be correct! I had to make the board a bit bigger to correct the errors. If anyone makes up any boards and would like to send me one that would be dandy!
(http://i210.photobucket.com/albums/bb292/frequencycentral/180PCBCorrect.gif)
(http://i210.photobucket.com/albums/bb292/frequencycentral/180PnPCorrect.gif)
Cheers !!
I'll sort one for you. PM me your details.
Paging Mr. Central to the white courtesy telephone...
Hey Rick. I am just about ready to "smoke test" my build of your phaser based on the layout info in this thread. I am curious about the resistors you show in one of your diagrams around the bias pot. Did you leave those in when you made the corrections to the layouts? In other words, do I need those resistors to make the circuit work?
I have high hopes for this guy, so I hope I won't have too many debugging issues. I'll know after my Saturday morning pedal building session tomorrow.
Thanks
Hey Doc! You know the perf layout has errors right? I revised the PCB layout but didn't get around to revising the perf yet. Though I did explain the 'fix' for the errors in the perf. If you use a 250K resistor for the Bias pot you should be fine, you don't need those other resistors. Good luck!
That was fast Rick. Thanks!
I do know about the errors. I actually used the corrected PCB layout you posted to figure out the connections. I have done a continuity check, and I appear to have everything connected per the PCB layout.
But, I thought the bias was a 100KB pot. It sounds like you are saying to use a 250KB instead?
Are the other pot values per your little "pots on perf" layout?
Chris
If you look at the schematic it's a 250K Bias pot. From my experience with the P45 build I did, I know the useful range is mostly in the middle of the range of the pot, so my idea was to use a 100K with fixed resistors. In practice it's easier just to go with the schematic, after all, it's just a voltage divider whatever value you use. If in doubt consult the schematic. I added the resistor between the bias pot and the width pot on the advice of Mark Hammer (I think), to make the range of the width pot more useable.
O.K. a 250KB bias pot it is. (I definately made good use of the schematic while building this...But I really appreciate the work you put into the layouts and your generousity in sharing them.)
I'll post my results after this weekend.
O.K. After a bit of further debugging, and finding out that as usual I didn't have all the correct connections the first time, I got myself a working phaser this morning. ;D
I LOVE IT! Having all those parameters to tweak makes this guy really versitile. So much more fun than a one knob MXR Phase 90. I love how resonant the sweep can be. I have been getting all kinds of filtery sounds out of it. And being a synth guy, I like me some filta!
Thanks Rick/FrequencyCentral for the layouts. Thanks R.G. for the circuit!
If anyone builds this, even on perf like I did, I recommend using the PCB to do your wiring. It is correct and easier to read.
Time do go sound like, "thrweeeeeshsssshhhhhhhhhzzzzzz......ChuggaChugga......................"
Hey good for you Chris! Yeah it's so much more that a phaser isn't it? Extreeeeeme! I'm curious as to what FETs and opamps you used. Did you have to do loads of FET matching? Good to know the PCB layout is verified anyway, I'll have to get around to correcting the perf soon...........
I used 2N5485's, a BC560, LM324's and a 4558. Almost exactly per your parts list. (I had some LM324's from a value pack I got from Futurlec, so it was nice to finally use those.) I had 28 2N5485's that I took Hfe readings for using my DMM. They ranged from about 798 to 805. I took 8 that were right at 800. The phase sounds very symmetrical, so I guess it worked...
I have really been enjoying experimenting with the pot settings. The names don't do them justice. I did use a 250KB bias pot, which works like a sweep center frequency control. The Regen works like a Q control for the filter effect. I left the mix pot 100KB like your pot diagram even though the schematic uses a 200k pot. It seems to be a decent range like this. But it is backwards on your diagram :icon_wink: so I switched lugs 1 and 3 so the "more effect" direction is clockwise.
I am putting this in a box with a Magnus Modulus I just built as my first introduction to etching my own boards. That too is a deep and extreme circuit. Kind of like a Tremulus Lune mixed with your own Clari-Cubed circuit without the fuzz. This will be my ultimate mod box!
A sad story, and a couple of questions:
Rick,
Sad story:
So, there I was loving this circuit so much...But when I installed it in a box next to my Magnus Modulus, I must have screwed something up because it stoped making any sound at all. I tried debugging it, but I decided that this was a good time to try my new PCB etching skils, so I etched the board and rebuilt it by pulling the parts off my perf version. I was very careful, testing every part before I reused it. But, the circuit only works halfway. It is filtering, but there is no sweep. If I adjust the bias knob, width or regen knob, I hear the filter being affected. But, there is no pulsing sweep to it. It is also self-oscillating a lot.
Questions:
I see that the schematic calls out for the Vref to be 3v. Right now mine is at 4.36v to 4.45v as I rotate the bias pot. Is there a reason you didn't try to get the 3v Vref? Would changing the zeneer to a higher voltage lower the Vref?
But more importantly, I believe there is an error in the PCB. Look at the attached image.
(http://img237.imageshack.us/img237/2301/phaserevolutionquestion.th.jpg) (http://img237.imageshack.us/i/phaserevolutionquestion.jpg/)
Shouldn't the tops of R12 and R13 be connected to the bases of Q4 and Q5? That is what is happening with R6, R19 and Q2,Q7. I started wondering when I noticed the pad for R13 is free standing and not connected to anything but one resistor lead. I guess I missed this when I was using the PCB diagram to debug my perfed version.
Thanks!
Quote from: doc_drop on October 12, 2009, 02:46:45 PM
Shouldn't the tops of R12 and R13 be connected to the bases of Q4 and Q5?
Ooops - you are correct sir! I'll edit and repost when I get the chance. An easy fix for you though...... :)
Quote from: doc_drop on October 12, 2009, 02:46:45 PM
I see that the schematic calls out for the Vref to be 3v. Right now mine is at 4.36v to 4.45v as I rotate the bias pot. Is there a reason you didn't try to get the 3v Vref? Would changing the zeneer to a higher voltage lower the Vref?
I figured it worked at what it was, so why sweat? But I'll do some experiments on mine and report back.
You sir are the promptest responder on the whole internet! I wanted to have you look at it before I made my "lil' bridges". But since you agree, I will make the change tonight, and report back. ;D
I don't know if I really care about the Vref thing if I can get it sounding as good as it did at first by making the little correction above. But, I am all ears if you want to experiment a bit with that.
Thanks again for such a quick response, as well as posting this layout. I really like this circuit...at least I will when I get it up and running again...
I've corrected the mistake and reloaded the PCB and PnP, so the images above are now correct, you may have to refresh you browser for the corrections to show. I really hate being human and therefore prone to error - why can't I be perfect like Mrs FC?
Well, something tells me Mrs FC couldn't whip together a perf board like you if she wanted to. Or maybe she can, in which case, does she have any sisters?...
My last 3 circuits have all been debugging nightmares, so I know how imperfection feels. It always cracks me up how happy I am to find my own stupid mistakes when I am debugging something. And I usually hate making stupid mistakes!
That did the trick! I created my 2 intentional solder bridges, and whammo, sweet phase - totally adjustable phase!
Guys, if you want to buid a phaser, do this one. It is verified and amazing.
Although it didn't come up yet, it may at some point.
One of the things often experienced as one adds more and more phase-shift stages is that noise accumulates. With the traditional 4-stagers, it isn't much of an issue, but once you get into 8 and more stages, particularly if you have intentions to use regeneration/feedback around those 8 stages, hiss can get aggressive.
There are a few potential solutions to this. One is to stick a suitable cap in the feedback loop of every 4th phase-shft stage. So, if one was using a P90 configuration with a 10k feedback resistor, stick a 1nf cap in parallel with that resistor on every 4th stage. That would get you a rolloff starting just under 16khz. If you don't ever plan to use it with acoustic guitar, you can up the cap to 1n5 and bring that rolloff down to around 10khz.
Alternatively, if you would like to keep as much bandwidth as possible, consider using a lowpass filter configuration in the regen path itself such that the hiss-reduction only really kicks in at higher regen settings. So, as an illustration, let's use the Ropez/Ross circuit. You can see a 27k fixed resistor leading to the "regen" point. Split that 27k up into a 12k and 15k resistor in series, with the 15k first in line. Now, run a 1nf (1000pf) cap from the junction of those two series resistors to ground. Voila, a 10khz lowpass.
In the case of the Ropez, I've found that the unit tends to break out into low-frequency oscillation when more than 4 stages are used (i.e., it starts to "moo"). You can fix that by reducing the value of the 1uf cap after the Regen pot to a smaller value, like .1 or .047uf.
R.G.,
Although I haven't spoken to him lately, Mike Irwin told me that although the drain-gate R-C network around the FET does manage to reduce distortion, in reality it functions more to stave off distortion to a higher threshold, rather than reduce distortion at all signal levels. His sentiment was that, although he held out high hopes for the R-C network to solve a S/N problem that was fundamental to FET-based phasers, the sound of the distortion that came into the picture at clipping point was simply godawful and an unintended penalty. In his mind, in retrospect it was worth dealing with the more modest distortion at lower signal levels to NOT to have to deal with the type of distortion introduced at higher levels. He went back to the no-network configuration.
Now, having said that, it bears noting that Mike is principally a synth guy, so the sorts of signal levels he might view as common enough to be higher risk might be generally way out of our league as guitar strummers. In which case, we would never, or only VERY rarely, exceed the threshold set by the addition of the R-C network.
An empirical question I suppose, resovable with a bit of signal-generator and scope work.
There is no doubt that at certain settings this circuit can hiss like...an angry cat?...
I find the externalized bias pot can tame that by simply changing the range of the sweep, or backing off on the regen. I guess what appeals to me is that you can adjust things like that to get a personalized sound, but it leads to some noise issues as well. Not to mention self-oscillation if you push it too hard.
Quote from: doc_drop on October 13, 2009, 12:14:32 PM
Not to mention self-oscillation if you push it too hard.
I added a 100K timmer to my build to limit the regen to just below self oscillation, easily done, just added it in series with R33. You do need to play about with the Bias and Width though, as their settings can subtly increase the regen. In fact, if I were to build it again I'd replace R33 with a 100K trimmer. Actually I am planning to build another one to go into my modular synth, as a kind forumite has offered me a PCB of my layout, and I have two more sets of matched FETs... :icon_biggrin:
I've got a few other experiments to run on this circuit, so I'll have a look at the noise reduction solution Mark suggests along the way. It's not as noisy as my Phase Evolution (http://www.diystompboxes.com/smfforum/index.php?topic=76657.0) though, but I used some old 4558's in that build (which I'm planning to replace with NE5532's).
Quote from: doc_drop on October 12, 2009, 02:46:45 PM
I see that the schematic calls out for the Vref to be 3v. Right now mine is at 4.36v to 4.45v as I rotate the bias pot. Is there a reason you didn't try to get the 3v Vref? Would changing the zeneer to a higher voltage lower the Vref?
I just experimented with changing the vref. What I did was remove the zener, then I took jumpers from vref and ground to a breadboard. I added different sets of diodes.
- One 5mm amber LED plus two 1n4148 = vref of 2.97 volts
- Two 5mm amber LEDs = vref of 3.47
I tried some different combinations going to ~2 volts and ~6 volts. The phaser effect gets more subtle the lower/higher the vref goes, and each different voltage requires a different position of the Bias pot to get the same effect.
The conclusion I have drawn is that I'm happy to stay at 4.09 volts. There's nothing to be gained from the option of having the vref switchable (to 3 volts for example), as the Bias control is king, it does the job for you.
.......and now I know that there's no reason not to use two 5mm amber LED's in place of the zener next time I build a FET phaser. :icon_biggrin:
Thanks for posting the info., Rick. I also tried replacing the zeener with a couple of other values with similar results, but neglected to post the info.
My only experiment left to try is to power it with 12v. I know you power all your pedals with 12v, so I am curious to see if it helps with headroom. I have a nice regulated 12v adaptor in the mail, supposed to get here tomorrow, so I'll post in a couple of days what my results are.
So, I received my new 12v 500mA regulated adaptor yesterday. I went ahead and powered the circuits I was playing with on my work bench with it, instead of the 9v cheapo switching adaptors I had been using. The whole "rig" definately sounded better. Everything was a lot cleaner, and I had more headroom. The phaser was deeper, although I had to fight back the self-oscillation a bit. But it definately is more usable at 12v.
All in all the one adaptor was powering my diy Ruby-ish amp, a Mosfet booster, a Tonemender, an MXR dist+, an Orange Squeezer, a Magnus Modulus and our friend FC's Phase Revolution. Aka lots of home built circuits. I am really happy with the clarity and headroom I got. I think it is 12v for me from here on out... ;D
Finally got a chance to iron out a couple of things that always bugged me about this pedal:
- I implemented the mix control from the BYOC Phase Royal. The issue I had with the stock mix control was a variation in volume through the sweep of the pot - very annoying as the pedal should always be at unity. Using the Phase Royal's mix control the effect is the same volume wherever you set it. Here's the Phase Royal schematic: http://dl.dropbox.com/u/967492/PhaseRoyalSch.jpg
- The pedal has always had very slight background distortion with humbuckers (I think this is endemic of Phase 90 varients?), sorting out the mix control left the effect's volume above unity, so the logical thing to do was to attenuate the input signal until the output is at unity. So, I've added a 100k trimmer to ground from between the 10k resistor and the 0.01uF cap at the effect's input. Tweaked for unity, the distortion disappears. Nice.
This pedal is now as perfect as I can get it. Sounds great now. I've done so many tweaks to it over the last nine months that I'd need to RE it to draw up a final schematic! Funny how solving a few of small but niggling issues can make you fall in love all over again............
FC, I have a list of phaser questions for you. Hopefully you have some time to respond to these.
1. Have you needed to use the suggested filtering methods to tame hiss on any of your phaser designs? E.g. Feedback cap on every fourth stage? RC filtering in regen path?
2. In the Phase Revolution you have used trim pots to dial in the regen just below oscillation, and also to tame hot HB input distortion. Do you still use this technique on some of your more recent designs? Do you tailor fixed resistor values (ie. socket)?
3. To add a fixed stage to any phaser, is the basic circuit you have used on the two ends of the causality design usable as is (e.g. following a P45 or P90 series of swept stages)? Do the resistor/cap values need to be tailored depending on the phaser stage circuit?
4. I'm planning on using the RG's P180 design (ie. Phase Revolution) and adding four fixed stages at the tail end. What do you think would be more useable switching: 4/8/12 (4 swept, 8 swept, 8 swept + 4 fixed) or 8/12 (4 swept + 4 fixed, 8 swept + 4 fixed) or something else. Or do you suggest switching different regen paths as more usable unique sounds? Also, any benefit to splitting fixed stages to front and back instead of stacking at the end? (Note, I'm not real keen on dedicating any stages just to the regen path, but if you think this is a more usable option, I'd like your thoughts on it. Mark has commented on this a few times.)
5. I was going to use a SPDT switch and use the two outer positions to ground out the unwanted stages. (e.g. one position would ground input to output for the second set of swept stages, eliminating it from the path) Do you foresee any problems with this approach, meaning I'd have to use dual pole switching instead?
6. What are your thoughts on various LFO circuits? Do you have a favorite for phaser, or do they all serve the purpose? The P90 LFO is nice and simple, but there are lots out there, some of which are easily adapted with a shape control as you've done in the causality.
7. For the mix control borrowed from the Phase Royal, do the 22k resistors work for the dividers, or did you use a different value? Did you have to adjust anything on the input/output circuit or the regen path with the change to this mix circuit?
I'm going to experiment on breadboard, but I'd like to reduce the number of variables if I can. Note that my end goal is a somewhat traditional P90 based phaser sound with more depth and a little versatility/uniqueness... but not a knob crazy Phaserlab. I have a hundred 2N5952's on the way, so I'm hopeful to match a set or two of 12.
Thanks,
Travis
hey im having probs printing this out at the right size so that the sockets fit right. what are you guys using to print this out. i have gimp and ms paint
Quote from: frequencycentral on April 06, 2010, 05:55:25 AM
This pedal is now as perfect as I can get it. Sounds great now. I've done so many tweaks to it over the last nine months that I'd need to RE it to draw up a final schematic! Funny how solving a few of small but niggling issues can make you fall in love all over again............
Hey Rick...
Have you been able to get a FINAL revision of the PCB for this project? I am very interested in getting this one built.
Thanks as always ;D
very nice, may i know what other options can be done for the BC557 ? :)