Tonepad Phase 45 Build Report

[RDV]

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

[Fret Wire]

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!

[RDV]

How 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.

For 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.

Does 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.

Try any different IC's yet?

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

I 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

[Fret Wire]

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

[RDV]

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

[keko]

trouble 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

[RDV]

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

[Johan]

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

[Fret Wire]

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.

[RDV]

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

Regards

RDV

[keko]

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.

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

[Jim Jones]

Hey RDV,

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

I agree, the 45 is fantastic!

Jim

[RDV]

Did 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

[Mark Hammer]

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.

[smoguzbenjamin]

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

[Mark Hammer]

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".

[Michael Allen]

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

Thanks,,
Michael

[Mark Hammer]

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.

[bwanasonic]

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

[Fret Wire]

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?