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I got the PCB I was waiting for from FP, and I excitedly populated the board using the Tonepad parts layout. I bought a bunch of 2N5952 JFets for the project, figuring I would socket them and find two that would phase nicely. Alas, I didn't have room for standard transistor sockets on the PCB, so I cut down an IC socket which worked great.

One thing I must point out if anyone is having trouble making this circuit work is that on the layout, they have the pinout backwards if you're using 2N5952, so you'll need to turn them around. However if you're using other Fets like 2N5458, the pinout will be correct.

I know I should have built a JFet matcher, but I'm lazy and figured I would just stick them in till I found a decent match. I found that if you stick one in at Q2 by itself and get quite a good bit of phase, then just stick one in at Q1 and adjust the trimpot to get some swirl happening. It's phasing pretty good right now, but before I box it I'll probably perf the Fet matcher from Geofex.

Thanks Francisco!

RDV

I've been thinking about using FP's pcb for that too. Glad to hear it sounds good! I"ll definately heed the pinout direction. How do you like it compared to the 90? Less pronounced?

For the speed pot, I've seen 500k lin and 500k rev. log. Which did you use? Almost forgot, does the pcb have enough room for metal film caps? Try any different IC's yet?  I think that pcb will fit in a 1590b.

Thanks RDV, not hard to tell I've been thinking about one of those, lol!

QuoteHow do you like it compared to the 90? Less pronounced?

I just like the musicality and the little Univibey knock it gets. You just want to arpeggiate for days.

QuoteFor the speed pot, I've seen 500k lin and 500k rev. log. Which did you use?

I used 500K linear, but I can see where RA would help smooth out the rate.

QuoteDoes the pcb have enough room for metal film caps?

Dunno. Depends on how big. The spacing(lengthwise) is the same as for a 1/4watt resistor. I also had to use a few 1/2watt resistors, but it really wasn't a problem standing them up to get them to fit. I just used the little film caps I got from Smallbear for the .047 & .01uF. For the 10uF, it's definitely set up for radial electros.

QuoteTry any different IC's yet?

Nope. I used TL072. What difference might a higher gain chip make?

QuoteI think that pcb will fit in a 1590b

It will, but would be a tight fit with jacks & a battery, especially with radial caps that can't be bent over. I wouldn't be able to put my power jack in my usual place. I think I'm gonna use one of my 1590S size boxes for some breathing room, but we'll see.

Regards

RDV

Thanks for the input. I just printed the pcb up to scale, yup, a 1590b will be a little tight. IC wise, I was thinking more in terms of noise, not gain. I don't know if the Burr Browns would worth the trouble price wise, but the NE5532 might be. Assuming they might make a difference. Thanks to TI samples, it won't cost me anything.

Cool to know that it phased without matching JFETs. I haven't gotten around to the matcher yet either.

Thanks again for the report.

Pete

I did however try a bunch till I got something cool. I bought 20. I've got some 5532 I may try. There doesn't seem to be much noise except for the whoosh.

Regards

RDV

Quote from: RDVtrouble making this circuit work is that on the layout, they have the pinout backwards if you're using 2N5952

darn darn darn! that frase got me thinking, so I went looking for that buried useless board populated to be my phase 45 but abandoned long ago!

Actually I used 2N5952. With these, and according to the datasheet, the drawing of the tranny on the board is wrong, BUT the ones I used had GDS printed on them. Quite a contradiction...

edit: the layout and the thatasheet had same pinout flipped, i.e. the case was drawn backwards, but the pinout was ok.

I never realized that I put them wrong!!!! First thing tomorrow mornig: bring that son of a...back.

thanks for noting that!...wooosh I'm soo happy

I got the thing to fit in a 1590B today, so it can be done. I had to remove one of the 10uF and put in another one with more wire on it so I could bend it over. I then just angled the board down under the in/out jacks with the other end resting on the power jack. Just enough room. This is the best thing since sliced bread. I'm gonna build another phaser. Maybe a Phase 90 or Small Stone.

Regards

RDV

try the easyvibe!!...there is an exelent layout at geofex, and it sounds great..slightly different from other phasers and defenetly worth a build...

Johan

Great! I was hoping it would fit in a 1590! Time to order a board. I think I'll try a 500k rev. log first. Also, I have some 10uf tantalums, so I might try one instead of the electro's. They're decent Panasonics, so they shouldn't affect the tone. I was thinking of going the MXR route with the board as close to the bottom of the box as possible, trace side out, component side facing inside. Then use a sheet of mylar or other heavy clear plastic to prevent shorts on the bottom, like Boss does.

This is a really good sounding Phaser, you gotta wonder why JD quit making them.

Regards

RDV

Quote from: RDVOne thing I must point out if anyone is having trouble making this circuit work is that on the layout, they have the pinout backwards if you're using 2N5952, so you'll need to turn them around. However if you're using other Fets like 2N5458, the pinout will be correct.

done! it works, and it rocks!

It is a subtle phaser, but very cool sounding. I'm thinkin of putting it in the same box together with my small stone...I tink there's enough room for both!

BTW, it sounds better (to me) with the 5952 than with 5458's. Also, I have to insist on this. My 2N5952 have a different pinout than the datasheet. Beware of that

Hey RDV,

Did Jim Dunlop make a Phase 45?  I didn't think that one got "reissued"...

I agree, the 45 is fantastic!

Jim

Quote from: Jim JonesDid Jim Dunlop make a Phase 45?  I didn't think that one got "reissued"...I agree, the 45 is fantastic!

I really didn't know if they had, I think they missed the boat, this would be a good circuit for somebody to start  producing.

I also tried the 'Univibe Mod'(10:1 ratio caps), but I'm not sure if I like it better than the regular caps, it seems to lose that nice swirl the stock caps give it.

Regards

RDV

I haven't attempted a P45 or P90 yet, but I have a little RockTek 4-stage phaser that is probably pretty close in design.  This unit uses 2SK30AY FETs for variable resistors (and the ubiquitous .01uf caps), and, to Rocktek's credit, seems to also use the distortion-reducing resistor/cap network between drain and gate as found on some of the Korg phasers.  

On board, there is a trimpot used for adjusting the bias voltage to the FETs.  Twiddling with it, I found I could get a variety of sounds since it essentially acted like a "manual phase shift" control for part of its range, by chaning the default resistance to ground.  I chassis-mounted it and am glad I did.  At both the upper and lower extremes of its usable range, you enter a zone where the phasing effect becomes less pronounced, but more "watery", not unlike a Univibe.

Worth tinkering with.

Would it be a good idea for the phase 45/90 you think?

In all likelihood, yes, though I can't say how much of the range would be useful.  It may be smarter to take that 250k trimpot and turn it into a 50k chassis-mounted pot with selected fixed resistors tied to the outside lugs to simulate a 250k pot (e.g., 100k + 100k, or 47k + 150k, etc).  The general idea is to expand the small amount of rotation on the trimpot that may be useful into more degrees of rotation on a pot aimed at mimicking that small select region.  How big that region is (and correspondingly, what the chassis-mount pot value should be) will depend on the FETs you use.

The best way to figure this one out is to play with the trimpot while you listen and determine if having easy access to the bias voltage gets you something you can use.

I have no particular opinion or way of guessing whether any chassis-mopunt pot ought to be log or linear to get optimum "dial-ability".

Mark, that sounds like an interesting project....do you have a schematic handy?

Thanks,,
Michael

It's not a "project" as such.  Just go to Tonepad (http://www.tonepad.com) and download the Pez90 and/or Pez45 layouts.  Both will have a 250k trimpot on board.  That trimpot sets a steady bias voltage to set the range of possible resistance change.  This is combined with the control voltage coming from the LFO.  It is no different at all, really, than the "manual" control found on a number of different flangers that use a steady voltage and LFO-voltage to drive the clock.

If you wanted to implement the 2-resistors-plus-pot thing I noted, do the following with a completed unit (either P45 or P90).
1) Set the LFO for a semi-fast/semi-slow sweep so you can hear the difference in tone over the sweep.
2) Pick one leg of the trimpot - my preference would be wiper-to-ground.
3) Rotate the trimpot to zero ohms, and slowly adjust the trimpot to increase the wiper-to-ground resistance until you just start to hear the phasing effect occurring. Measure the wiper-to-ground resistance and make a note of it.  We'll call this R-start.  Determine the nearest standard-value resistor. (e.g., if it's 37.3k *or* 41.1k, we'll call it 39k)
4) Continue rotating the trimpot.  You will hear the phasing move either upwards or downwards in its range.  Same *amount* of phasing sweep, just over a different part of the spectrum.  Once you hear the phasing appear to stop (i.e., sweeping seems to peter out then stop), measure the wiper-to-ground resistance and write it down.  We'll call this R-stop.
5) Work out the difference in kilohms between R-start and R-stop.  Find the nearest standard-value pot that is either just a tad bigger or a tad smaller than that value.  Add up R-start and the estimated pot value, and figure out the nearest standard-value for resistors that will get you 250k.  (e.g., with a 39k R-start, and a 100k pot , the closest resistance value for the 2nd resistor would likely be 120k.  If you really want to be picky, I suppose you could always sub a pair of fixed selected resistors whose series resistance added up to the "ideal" value on each end of the pot.
6) Run leads from pads where the trimpot would normally go to the wiper, and outside lugs of the pot, with the additional fixed resistors going in between the leads and the lugs.

I don't *think* that needs a schematic but I'm sure someone here will eventually draw one up if that's necessary for maximum clarity.

To any Phase 45 builders: be sure to try the *univibe* cap values. Click on the Links above for a link to the post about this. Also cool blinking LED mod and increased speed mod. Also note that the DOD 201 is another nice P45 type *phasor*.

Kerry M

Is this the schematic?

http://www.lynx.bc.ca/~jc/phase45modded.gif

What about a simple level (volume) control? Wouldn't that be in place of the 150k?

Son of a gun.  I'm not sure if this means that great minds think alike or that fools seldom differ, but JC's schematic that you linked to shows pretty much exactly what to do with respect to chassis-mounting the bias control.

The 150k output resistor can probably be replaced with a 100k linear pot and a 47k resistor between the ground lug and actual ground for volume adjustments.  On the other hand, this thing is designed for unity gain, so I don't know what value there is in adding a volume pot.   Maybe, if you upped the gain on the input stage, but then that would likely distort the FETs.

Thanks Mark. I was just thinking that because sometimes, depending where in the effects chain the phaser is, the level gets boosted when the phaser's on. It would be nice to dial it back to unity.

Mark, I understand the idea,,,, I was just wondering if you had a schematic for that RockTek Phaser?

Nope.  No schem.  On the basis of the components on board, I'd say it isn't too much different than a bunch of other phasers like the Vox or Ibanez PT90.  Essentially the identical structure (dual op-amps, 10k input and feedback resistor and 10nf input cap for each section, FET to ground, dual op-amp LFO, single FET-switching for effect bypass).  The only major difference between this and things like the P90 is that the effect switching is done with a 4027 or 4053 (I forget which, and I'm at work now) instead of the discrete-based flip-flop in "name" pedals, and there is a cap/resistor combination between gate and drain on each FET to reduce distortion (see the Korg and Ibanez phasers for examples of this).  And, of course, the FETs are K30's instead of 2N5952's.

Tracing it out is probably a nonstarter these days.

Would a Phase 45 benefit from a higher input impedence, like a unity gain buffer? Mine sounds a little funny with a distortion driving it.

Regards

RDV

What I always noticed with the Phase 90 (basically the same) is if you put it after a distortion or overdrive, the phasing effect is way more pronounced. It also seems to boost past unity gain. With the speed all the way down it even starts to sound more like a flanger.

Quote from: RDVWould a Phase 45 benefit from a higher input impedence, like a unity gain buffer? Mine sounds a little funny with a distortion driving it.

I always use mine before distortion. Sounds more univibey. Try it. Wah-Phase-Fuzz Face is the combo I really like.

Kerry M

Quote from: bwanasonic
I always use mine before distortion. Sounds more univibey. Try it. Wah-Phase-Fuzz Face is the combo I really like.

Kerry M

Same here. Like I said above, if you use a phaser after the dist., it seems like double the effect. If I use it after a dist.+, fuzz, or DS-1, I have to leave the speed all the way down or it's useless. Maybe that's what you're hearing, RDV. It's even worse for someone using the reissue phase 90, with the added distortion in the unit. Used before the OD's/Dist.'s, the full speed range still comes through with the nuances. Flangers and Chorus's behave the same way. Sometimes, it's a cool effect for the phaser or flanger after the distortion pedals. Can give an EVH sound.

I haven't had a Phaser since I was a kid(Small Stone), & I sold that one. I really didn't know where in the signal chain they normally go. I just wondered if everybody else's sounded weird after distortion. Now I know.

I also didn't like the Univibe mod. With a Phase 45 it just seemed to take the swirl away, I bet I would like the mod on a Phase 90 as it is a four stage unit like a Univibe.

My particular Phase 45 may not have taken well to the mod though I think maybe cause I didn't electrically match the Fets, I just plugged them in till I found something I liked, which to me sounded kinda univibey already, so when I did the cap mod, it just seemed to make it sound so linear in the sweep, and actually undo the univibeyness(is that a word?).

Thanks

RDV

Okay, here's the deal.

1) Anything that provides a filtering action will have a more noticeable filtering action if it is provided with a harmonically richer signal, or any signal whose spectral content is pretty full from low to high.  So, your phaser/flanger/wah will have a very robust effect if it is inserted after a fuzz or processing white noise or a cymbal, and appear to not be working at all if you process the subwoofer output of your electronic crossover.

2) We too often forget that filters of every kind are inherently amplitude-altering devices.  That is, they reduce the amplitude of this part or that part of the frequency spectrum.  If a filter is swept around, what that means is that there will be a shifting impact on the amplitude of parts of the signal.  Some parts will stay unaffected, while others will get louder and softer, depending on what the filtering is doing at the moment.  Should there be any resonant peaks in the input signal being processed, filters can also momentarily *increase* the loudness of those peaks if there is any gain/emphasis built into the filter.

3) Distortions are largely threshold-based devices.  That is, signals below a certain threshold will have little harmonic content added to them, while signal at or above the threshold will have sharp increases in how much harmonic content is added.

When you put #1, #2 and #3 together, what you get is this.  
As the flanger/phaser/wah sweeps, there are peaks and dips introduced in the spectrum.  If the filtering action occurs after a source of rich harmonic content, it will have no effect on what harmonic content is generated but will have an effect on what part of that is heard.  

If the filtering action is inserted *before* the distortion, it will have a very different effect in that it will vary whether different parts of the input signal fall below, at, or above the threshold for clipping.  So, perhaps, that part of your signal in the 900-1200hz range is just right for producing harmonic content as it passes through your clipping stage (fuzzbox), but as the notches in the phaser pass through that zone, momentarily that range falls below clipping threshold, and then resumes "clipability" when the notches move elsewhere.

So, inverting the order of filtering pedal and distortion device alters what harmonics are being generated, as opposed to what existing harmonics/bands are being heard.  If it was the case that distortion devices only generated a single overtone (say, double the input frequency), then the harmonic content would seem to track the notches in an obvious manner.  However, distortion devices sprinkle the entire audible spectrum with harmonics of what you feed them, such that an input note of 300hz will generate harmonic content way up past 10khz (very often the upper limit of amp speakers).  As such, the shifting notches and peaks don't really eliminate harmonics as much as alter their relative distribution.  There may well be a dip at 2khz introduced by the flanger, but there is harmonic content in that band from lower notes as well.

Like Bwana, I too find that a phaser before a fuzz sounds more Univibey.  Bear in mind that the cap values in a Univibe result in broader distribution of phase, for want of a better descriptor, so that cumulative phase shift is not focussed or clearly different at some specific frequency.  This results in less peakiness/dippiness in Univibes.  I think the way that phase shifters will effective shift the balance of harmonic content (in the manner described above) when placed before a distortion device does the same sort of thing.  That is, it results in a more diffuse, rather than focussed effect on the signal, yielding a more animated sound.

The down side is that a consistently strong signal is essential to using any distortion as means to sustain a note.  Since the phaser will vary the amplitude of the signal through its filtering action, notes held via finger vibrato will behave very differently in the phaser-fuzz arrangement compared to the fuzz-phaser arrangement.

Having said all of that, you can see why a fuzz-phaser combination pedal with a sequence-flip switch would be a nice thing.  That would need some kinda switch, though, if you wanted to do order-flipping AND have a status LED.