Maestro PS-1A layout...for your pleasure

[jdub]

For them's who's interested:
I haven't found a DIY version of this legendary phaser, and always wanted one, so here's my shot at it. This is a condensed/modified version of the original board, put together from various gutshots; still bigger than I would like (right around 5" wide), but a smaller layout is a project for another day.  I'm using the GGG bipolar power supply for this- tried an LT1054 doubler/inverter but this puppy apparently draws more than the ~50mA or so that that circuit supplies.  Still playing with conversion to a single supply.

So far, it sounds pretty good, but bear in mind that I don't have an original to compare it to.  The ramping feature on this phaser is pretty sweet.  IMO, it would benefit from adding foot-controllable speed and doing away with the three switches, but I haven't had time to play with it yet.  Should be easy to implement, though.  In fact, it looks like the board could fit (snugly!) into a wah shell...

Tranny numbers are listed...I initially tried matched 2N5952 FETs but couldn't get 'em happening; the 5485s seem to work well.  They were matched using the Greatly Improved FET matcher here: http://tagboardeffects.blogspot.com/2012/07/greatly-improved-jfet-matcher.html There may be better subs for the original 2N4303 FETs and the 2N3638A bipolars, but these seem to work well, though socketing is a good idea.   I'll try to get a BOM up soon.

One other thing:  the 10uF polarized cap in the middle of the layout isn't on the schem and was only present on one board, but I threw it in anyway.  Probably not necessary.

Anyway, enough yakkin'.

Schematic:


Layout:


Transfer:


Enjoy!

[Cliff Schecht]

I posted a thread about one of these a while back. The one I messed with was built into an SG Systems amplifier and was an absolute blast to play with. Been wanting one ever since. Glad to see someone else taking interest in this pedal, it's a true classic that I think deserves more love than it gets.

[jdub]

Couldn't agree more...it's got a beautiful swirl/throb thing going on that I haven't heard in many phasers, almost Vibe-like.

[John Lyons]

Awesome! Nice work.

[newperson]

nice add and vintage style tracing.

[Steve Dallman]

Excellent! I had one for years and still have a couple SG's with them in. Besides the great phasing, the switches are unique. Forget a speed control. The slow and fast speeds are set at the two speeds of a Leslie and ramp up and down when switching between the two. You won't match that ramping with a pedal. THAT is the best feature of this pedal.

Plus, it sounds great on bass as well.

[juansolo]

I wondered where this layout came from! Cheers dude. Just built this and it's a stormer! FWIW the 2n5087 on the input is backwards on the layout. As are all 6 of the 2n5485s. The HA17458 opamps we got from Tayda work, which is good as other things we tried didn't. It's worth adding the 5 RF surpressing caps underneath the board also as it's good at getting radio with out them.

As the board needs +/-12V. We've used a 12V supply with LT1054 on Madbean's Road Rage for -12V. Hopefully it will work with Madbean's new dual charge pump circuit at 9V when it lands as we found trying to do it with a single didn't yield as good results as a 12V source.

[jdub]

Nice work, man!  Looks and sounds excellent.  Sorry about the backwards trannies, once again I uploaded the wrong version of the layout- I have about 10 revisions of it saved and used the wrong one.  Correct one is now in my layout gallery (http://www.aronnelson.com/gallery/main.php/v/jdub/Maestro+PS-1A+layout.png.html) or here: http://i1220.photobucket.com/albums/dd454/jdub5248/MaestroPS-1Alayout_zpsaeda6660.png.

I love this phaser, it's my favorite so far.  If I may ask, how did you wire your stomp switches?  Did you go true bypass?  I'm about to rehouse mine- my prototype just has spst switches and no LEDs, and I'm trying to decide how I want to do the stomps.

I had to use the 47pF RF blocking caps, too- the radio stations were louder than the effect at times.  I also had to do some LFO deticking- used a TL062 as well as some surgery to install a 100R resistor  to the +12 pin and a 22uF to ground. 

I bet it would work well on +9/-9V, but I already have it set for +12/-12 from an AC adapter, so I'll just stick with that, I guess.

Cheers, man! Glad you like it! 

[juansolo]

I tried it at +9/-9V and the lack of headroom in comparison to +12/-12V was surprising. I wouldn't recommend it. Indeed I've thought about going +15/-15V like the Oberheim.

It's wired true bypass. The slow and common are linked so it's always on, and the in/out just go to the optical switch board (could just as easily be a 3PDT). The only downside is there is a little bit of a volume drop when you engage the effect.

No issues with ticking on this one.

But yeah, it's a stunning phaser. The speeds are nigh on perfect, the ramping effect is cool as hell and it just sounds damned good. Well worth a build and many, many thanks for doing the project!

[pinkjimiphoton]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!  !  ! !!! ! 

[Kipper4]

sweet swirly madness love it . Good work

[yearofrolling]

I hate to newb out on you, but are those DPSTs or DPDTs?
Also, if that BOM is hangin' around? That'd be pretty cool. I can make one, too, if not.
Thanks!

[danielzink]

I hate to newb out on you, but are those DPSTs or DPDTs?
Also, if that BOM is hangin' around? That'd be pretty cool. I can make one, too, if not.
Thanks!

You've got the new layout which lists all values right on it.

Not much need for a BOM at that point.



Dan

[tomas1808]

Just finished my Maestro breadboard using the original parts. Sounds great!!

It is working perfectly but there might be something slightly wrong with mine because I had to remove the 10K resistor going from the FET BIAS trimpot to -12V rail to increase GATE voltage and get the FETs to modulate nicely.

With the 10K resistor I could only get -2.6V max on the FETs Gate which was not enough to get phasing. Can somebody measure their GATE voltages? There is either a small mistake on my breadboard or my FETs have a very high Vgs.



Here is a BOM sans the PSU:

https://mega.co.nz/#!ksokXRID!C213mSAKWfWWMXkVyuIy7y-gevld-6ygnZVrvsoT5LY

Thanks jdub for the PCB layout, will be using it soon!

[duck_arse]

with the 10k fitted, you should be getting from -6V to 0V at the pot wiper. with no 10k, you should be getting -12V - 0V at the wiper. you can put the 10k to 0V and the pot to -12V, in which case you'll get -6V to -12V, if your fets are a bit high Vgs wise.

[tomas1808]

Thanks, I'll check my voltages.

I am a bit put off by the amount of hi-frecuency loss. Didn't expect this amount.

Adding true-bypass only made this loss more apparent.

Any ideas on how to reduce the hi-frecuency attenuation?

[duck_arse]

check all your 50pF caps really are only 50pF. I don't think there should be much high attn, perhaps there is another error lurking. you'd want one of the experts to clarify what or where.

[jdub]

+1 on checking the 50pF caps, if you added them.  I notice on your BOM that you have those caps listed as 0.47pF; are you sure you didn't accidentally use 0.47uF? 'Cuz that would sure cut a lot of high end ...Apart from that, I'm not sure what to check other than maybe the input cap.  I don't really have much high-end loss at all with mine.

[tomas1808]

No, they are 47pF, sadly.

I put 47pf in the BOM because 50pF seems hard to find I think? 

There must be something wrong with my breadboard. I'll check.

If I dont find anything I'll go for the PCB and hope it fixes itself!

Thanks

[duck_arse]

erm, it struck me the next day, of course. if your fet bias ain't right, it'll affect the tone. that's why I'm going with a panel mount bias on my (soon) phase 45, you can shift up and down sweepwise.