Maestro PS-1 Phase Shifter - anyone tried to clone one?

[polaris26]

I am looking for info on the Maestro (6 stage) Phase Shifter - the one with the three speed rocker-switches on it.  I have a schematic, but I think some of the parts could be subbed for ones I already have.  Has anyone tried to clone one of these?  If so, what parts did you use? 

I do have a collection of JFETS that I matched and sorted back when I was building Phase 90's.  Could these types also work with the Maestro circuit? 

Also, I was thinking that I wouldn't need to reproduce the three-speed switching circuit, unless it contributes something to the sweep of the phaser.  I'm not sure what the LFO waveform would look like from this circuit as opposed to the Phase-90 style LFO, but having infinite range of sweep speeds I think would be a nice touch instead of only three speeds.  Any thoughts?

Dave

[vanessa]

It may be my favorite phaser of all time. I think it gets looked over because most have not heard it before. I also think these might have been expensive pieces back in the day, and may account for their lack of popularity amongst the average musician. Just put on the beginning of "No Quarter" by Zeppelin and you'll hear what a cool piece it would be to have in your collection.

The three speeds are really two and a on/off switch. It's a 6 stage phaser that had a really full phase sound by comparison to the Phase 90's and other's out at the time. If you like P90 phase over the others, the Maestro is your phaser. You could do a number of mods to it including switching in and out stages (P45, P90), cap changes for Uni-Vibe etc.. The speeds were setup to emulate a Leslie and it does a convincing job. I don't remember if they ramped up or down or not (me thinks not), but that would be an excellent mod to this piece as well.

[John Lyons]

Sounds like a good one to clone for sure. Hopefully someone will take you up getting this cloned. I don't have the time!

John

[polaris26]

I was actually turned onto the Maestro PS-1 while trying to find out which phaser Alex Lifeson used on the early Rush albums, and specifically on parts of "Lakeside Park".  Somewhere on the net it referred to his use of Maestro phasers, so I began to look into them.  Then I came across the John Paul Jones reference and I knew this was an effect I would like to re-create.  After looking at the schematic, I thought some of the parts could be simplified or done away with, but then again, it really isn't all that complicated, so perhaps for authenticity's sake, I should make one as-is.  I don't have the proper JFET's but as I mentioned I do have matched sets for Phase 90's  (2N5952 I think), so I will probably start with them and see how it goes.  By the way - if anyone needs matched JFETS, I will have some of these left over ( I bought 200 and used the op-amp jfet matcher to sort them into clusters matched within 4mV).

Dave

[caress]

i'm pretty sure it is a ramp up/down style.  check out some of the soundclips from mode zero...
http://www.modezero.com/maestro-ps1a.htm

[vanessa]

i'm pretty sure it is a ramp up/down style.

Yeah I think it was. And I think that was another one of the reasons I really liked it. On guitar it really was a beautiful effect. It was very much the "Leslie" in a box for the day.

After looking at the schematic, I thought some of the parts could be simplified or done away with, but then again, it really isn't all that complicated, so perhaps for authenticity's sake, I should make one as-is. 

I'm sure a charge pump could help this one out. I doubt it has a big current draw. I'll have to look at the schematic again. It would be really cool with 3 stomp switches. The unit I had (and most of them for that matter) was missing the stomp adaptor. You had to be very careful to push the rocker switches back and forth with the tip of your toe because you could accidentally turn on one of the other switches (I think the faster speeds override the slower when that happens). I think I would much rather have the 3 switches over a single dial. I have phasers with speed controls. This would react more like a Leslie. Then true bypass the off/slow switch (on/off).
What would be really cool would be to add a Uni-Vibe mode to this one. I think with 6 stages it would be very "Vibe" like. I've done Uni-Vibe mods to 4 stage and 2 stage phasers and the effect it rather weak (better on a 4 stage but not there) by comparison to the real thing. I think a 6 or an 8 stage (it would be easy to tack on an additional stage to this one) phaser with the "Vibe" cap mods would be the ticket. Anyone agree?

[ulysses]

i dont hear any ramping on those mode zero clips.

the mode zero guitar clips dont give a very good example of what the maestro sounds like.

the univibe was a 4 stage phaser.

cheers
ulysses

[polaris26]

In looking at the schematic, I guess the 220uF cap across the base of the emitter-follower transistor that establishes the source voltage for the LFO JFET is what allows for the Lesliesque ramping.   The parts breakdown doesn't specify the type of JFET used for the six phase-shift stages, it just says "FET, N-channel, Matched Set of six"   There are other JFETs used in the circuit - one for the LFO and one for the mixing of phase-shifted & dry signals (the gate of which is used to control whether you have "off" or "slow" phase - tied through a resistor network to the first rocker switch I suppose.  It seems like a funky way to blend the two -  why wouldn't you just put a switch on the phased output to open up that path when you wanted dry out only?  In any case the unit is of course not true bypass, as the signal always goes through an emitter-follower buffer at the input.  This is where cloning old effects gets funky - do you re-do the sections that you think could be done better, or do you try to be as true to the original sound as possible (since it worked back then, it must be good now)?  If you keep that output-mixing JFET in there, what type do you use?  It calls for 2N4303 which seems expensive today - I guess you could just use the 2N5952's throughout?

Dave

[ulysses]

rg would be the man to ask about the ramping.

when it comes to cloning old effects its fairly common practice to update the parts of the circuit that dont effect the tone by using more effecient methods - bypass switching - buffers - switching modes that my not be desirable to create a simpler circuit.

rg recently modded the phase 90 and the ea trem (two completly different circuits) to contain the "same essence of the tone" as the brownface vibrato.

another example is son of screamer which is the "core tone creation" of the tube screamer without unneccesary buffered switching.

cheers
ulysses

[polaris26]

Is part of what people mean by "Univibing" using staggered cap values for the phase shift stages?  The Univibe had staggered cap values which I have found in simulations decreases the slope of the "linear portion" of the phase vs. frequency plot of the all-pass filter as a whole, and thus spreads the notches further apart.  I would imagine trying this with a two-stage phaser would simply result in a changed notch center frequency, which would of course sound different, but since there is only one notch, then there is no spacing between notched as you would have with 4 or more stage phasers.  I think you have to be careful with 6 or more stages to space the notches in soncically interesting areas for whatever instrument you have running through the effect.  I liked using staggered values in the Phase 90 - it seemed to give it a "chewier" sound to my ear - much like the Univibe itself.  I am wondering if as a 6-stager were swept across it's range, the highest notch would pass right out of audibility - you might need to play with notch spacing and sweep range to get it all worked out - I usually do things on a solderless breadboard just so I can play with all the values and test by ear.

Dave

What would be really cool would be to add a Uni-Vibe mode to this one. I think with 6 stages it would be very "Vibe" like. I've done Uni-Vibe mods to 4 stage and 2 stage phasers and the effect it rather weak (better on a 4 stage but not there) by comparison to the real thing. I think a 6 or an 8 stage (it would be easy to tack on an additional stage to this one) phaser with the "Vibe" cap mods would be the ticket. Anyone agree?

[vanessa]

Check out this sample for the ramp sample, It sounds pretty convincing on a guitar (not so much on a synth).

http://www.modezero.com/sounds0000/rs09a-maestro-ps1-3.mp3

I think the Uni-Vibe mod would work good. You would have to figure out the staggered cap values for a 6 stage phaser (or better make this an 8 stage? Very easy to do). If not you could have it where you could switch in/out stages and switch in the vibe mode for the 4 stage only. I really think staggered caps on a 6 stage phaser would be the ticket.

A pulse LED would be cool, as would a feedback loop (for spacey phase stuff).

J201's for all the JFET's. They seem to be the magic JFET's for these types of phasers.

[ulysses]

hmmm.. i dont hear ramping in that sample.. 

except momentarily when the speed is switched slow and fast.

cheers
ulysses

[vanessa]

I definitely can hear it, all be it subtle it's in there. It's not like it goes slow right to fast. A value change here or there might make it more pronounced. To me it's close to a real Leslie ramp. When I got my first Leslie I had expected it to ramp up like a helicopter. I was supprised to find the transition to be rather quick.

[box]

Hi,

I have just finished a Maestro clone. I used a Traco Power TEM2-0521 (DC / DC converter) to power the system.Circuit consumption is 140mA.
The power supply is a 9V adapter, a 5V regulator and Traco Power(+/_12V +/_80mA---2W).
Regards,
box

[kaycee]

Pictures please 

I would dearly like to build one of these, I really would. There are a couple of people making clones of it, but no one selling a PCB. I tried a vero, but couldn't get it to work properly after much time and effort.

[Ry]

Madbean has a few boards available for what I assume is this model, here's a link to the build doc:

https://www.madbeanpedals.com/projects/_folders/FilterMod/pdf/StageFright2015.pdf

[Mark Hammer]

The Madbean schematic is a clone of the later-issue MP-1, not the original Oberheim/Maestro unit.  It is also a 6-stager, but uses OTAs instead of FETs, and has a continuous speed control, rather than the 3-speed arrangement with ramping.  None of that is a "bad" thing, but may not be what you're aiming for.

[box]

Pictures please 

I would dearly like to build one of these, I really would. There are a couple of people making clones of it, but no one selling a PCB. I tried a vero, but couldn't get it to work properly after much time and effort.

Hi,
I am sending materials that may be helpful.

[Ry]

The Madbean schematic is a clone of the later-issue MP-1, not the original Oberheim/Maestro unit.  It is also a 6-stager, but uses OTAs instead of FETs, and has a continuous speed control, rather than the 3-speed arrangement with ramping.  None of that is a "bad" thing, but may not be what you're aiming for.

Thanks, Mark!  I didn't realize that there was more than one Maestro phaser.

[Mark Hammer]

The phaser your hear here is the Oberheim/Maestro unit that box provided drawings for.  I know because I went to see them when the album first came out, and saw it when I walked up to the stage before the show.