MOOG Moogerfooger MF-103 12-Stage Phaser  [schematic]

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iznogoud
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Post by iznogoud »

Techniguitare, MDR, Je connais Shaddo IRL [smilie=a_biggrin.gif] Enfin, j'espère bien ne jamais le revoir. Dire que j'ai accueilli ça sous mon toit :thumbsdown

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johnnyg
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Post by johnnyg »

I didn't know where to ask this question on the forum, but hoping here might get a response:

I've been looking over the schematics for the Moog designer 1970s Maestro (MP1) Phaser and Maestro (MSP-274a) Stage Phaser for a few days - and I've built the (simpler) MP1 Phaser using LM13700N in place of the original CA3094. No adjustment to the circuit whatsoever to suit the LM13700N.

This works... but my feeling is it may not sound as good as it could... particularly from hearing demos online of the Stage Phaser (it sounds much better). Now I know the Stage Phaser is a more complicated beast and there are more than enough differences between that and the cheaper/simpler MP 1 (like a different LFO) to mean it will sound a bit different to the MP1.

However, I've been wondering if the different transconductance amplifier has an impact - especially after looking at the Moogerfooger which is designed for the LM13700N.

Before I start the (for me) epic task of attempting to hack the MP 1 circuit on the breadboard - attempting to replace the phase stages with the six stage LM13700N chain from the Moogerfooger - would anyone more knowledgeable (i.e. just about everyone else on the forum :lol: ) be able to tell me if there will be issues I haven't realised?

The reason I've had some concern there may be is the use of a split rail power supply. Looking at the LM13700N datasheet, this is the recommended manner of using the IC in the example circuits. So I'm thinking to get the best out the IC it's the way to go... and Bob Moog would surely know after all.

If I'm keeping the rest of the circuit as the MP 1, with the single positive 9 (or 12?) supply and ground, will just using a negative 9 (or 12v?) supply at the output of the Darlington Stage be ok - or cause issues...

... or am I getting way out my depth here! :D

The reason I ask about using 12v is I believe the Stage Phaser ran on this (to light the bulbs) - possibly another factor in the improved sound?

Before anyone says why don't you just try - I have to go buy a more sections of breadboard :lol: (as I'd be splitting the circuit up into constituent blocks to facilitate the attempt hacking).
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johnnyg
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Post by johnnyg »

I should have added this link to my question: it is Volker's project for the Moog designed MP 1 (utilising the LM13700N):

viewtopic.php?f=13&t=5818&hilit=meister+maestro+phaser

Could anyone see likely issues with replacing the phase stage chain with that from the Moogerfooger stage phaser (just the six stages)? Excuse my ignorance if they are obvious.
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Post by jdelgoulet »

Hello everyone. First post on the forum ;-)

I want to have a try at this schematic and transform it to a layout. There is one thing confusing on the schematic. Q4 and Q5 are noted as 2N4401 which are NPN transistor whereas, they are drawn as PNP (VCA part of the schematic).
Could someone confirm which one is the good one ?

PS : I did a try of the VCA using 2N4403 (so as drawn on the schematic). Works great despite one thing. It seems that the "AmountPot" range is only between 0% and 35%. Above, VCA output a DC voltage ... (I did not add the sweep part by the way and use a linear pot for the "amount" ...).
P2 : are pots log / lin ?

Thanks everyone !

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beneat
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Post by beneat »

Thank you very much for this schematics.
Have a good day!
Pat

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Post by loylo »

alain-mac wrote: I've checked the schematic and found it is ok up to a small detail concerning the connections to the "positive" VCA output. RN3-2 should be connected to RN3-3 and PIN 3 of U10A what is the positive input VCA.
In the schematic RN3-2 is connected RN3-3 and R34 and so we short input and output of the allpass filter.
Hello,

I agree with you, Alain. In my opinion the schematic is wrong in the area you have pointed.
But I think your correction is wrong too.

U10A should be configured the same way as U10B.
So RN3-2 should be connected between C24 and pin 3 of U10A, just like RN3-1.
RN3-3 should be connected between R34 and pin 4 of U10A. Just like RN3-4.
So RN3-2 and RN3-3 shouldn't be connected together.

I just bought a withe special editin of the MF-103. I'll try to have a look in order to confirm my suggestion.
But my version of the MF-103 seems to be SMD...

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KevinMitchell
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Post by KevinMitchell »

Hello! This must be my first post on this site. Perhaps some of you will recognize my name from the other stompbox site. I wanted to share my experiences here - with the origin of the project. I've considered all corrections and have worked up a vero layout for 6 phase stages and a more minimalist approach. I'd like to build a good OTA phaser for guitar and although this require much work, I'm definitely diving in.

I've managed to find some free time to put this layout together. I'll work up a schematic to accommodate my connections. I wanted to share this UNVERIFIED layout in hopes that anyone would take interest and perhaps spot any errors. Other than half the stages and omitting the soft touch bypass I've also left out the power supply for now. I apologize for the unlabeled standing resistors :roll:
Image
FULL IMAGE

I'll check repeatedly as I find the time. I hope to start soldering this weekend. I'm not 100% on the pot values since I'm going off of memory. Months ago I've done an immense amount of research and to the best of my ability retraced the PCB using any images I could find. I had notes on the values but I can't find the dang schematic in the jungle of prints in my work space...
I hope this site is lively!

Best regards,
-KM

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Dimitree
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Post by Dimitree »

other possible mistakes in the schematic:

1) the moog manual says the LFO output impedance is 600ohm, here it looks like 2.2K, right?
2) looking at the guts, R67 is connected to the same track of LM13700 vdd pin. If so, R67 should be connected to 9V and not 5V. Maybe some other parts too in that area?
3) I did a spice simulation of the LFO, and looks like you need a resistor (1M or 2.2M?) from U14C + input to +V, otherwise it won't oscillate

what do you think?

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Post by Dimitree »

also, I see a LM339 on the pcb, but not on the schematic. What could it be used for?

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Post by Bernardduur »

Here's the power supply!
Attachments
MOOG - MF-103 PSU.JPG
'No more....... loud music.......'
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Dimitree
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Post by Dimitree »

Cool! Do you have the chance to check the possible mistakes I noted some posts above?

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KevinMitchell
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Post by KevinMitchell »

I'm back. Sadly dropbox took all public files down. I may have my own MF103 next week. If I get it I'd actually like to redraw the schematic in full and a copy of the PCB for a true clone. From there I'll very likely work up a downscaled - 6 stage, true bypass clone to fit in a 1590B enclosure.

The project has not died 8)

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Post by toneman »

Have u seen the Music From Outer Space (MFOS) 8stage phaser?

It uses LM13700 OTA's also.

http://musicfromouterspace.com/analogsy ... ER2007.php

a nice pcb is available.

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Dimitree
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Post by Dimitree »

KevinMitchell wrote:I'm back. Sadly dropbox took all public files down. I may have my own MF103 next week. If I get it I'd actually like to redraw the schematic in full and a copy of the PCB for a true clone. From there I'll very likely work up a downscaled - 6 stage, true bypass clone to fit in a 1590B enclosure.

The project has not died 8)

Cool, can't wait!

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Post by Chorusjunkie »

Any update? :D

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KevinMitchell
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Post by KevinMitchell »

Chorusjunkie wrote:Any update? :D
No not yet. This morning I was browsing the internet market to see what's available. Not looking good for the old through-hole units. So it'll be a waiting game and strike of luck before I have one to reverse engineer myself.

I might put up adds soon. Or at the least give it another shot on breadboard.

I'm really interested in the unit because it has an envelope trigger where the LFO is progressive with your strokes. So if you stop playing, the lfo pauses and picks back up where you left off. I can think of a few effects where I'd love to have that function.

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Post by Dimitree »

KevinMitchell wrote: I'm really interested in the unit because it has an envelope trigger where the LFO is progressive with your strokes. So if you stop playing, the lfo pauses and picks back up where you left off. I can think of a few effects where I'd love to have that function.
Are you sure about that? I can’t see any link between the LFO and the audio signal that would probide that functionality, at least on the available schematic

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Post by KevinMitchell »

Dimitree wrote:
KevinMitchell wrote:Are you sure about that? I can’t see any link between the LFO and the audio signal that would probide that functionality, at least on the available schematic
Nope. I was wrong :roll:

It was a demo video I seen a while back that gave me that impression (using an external sweep signal). My bad.

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KevinMitchell
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Post by KevinMitchell »

Dimitree wrote:also, I see a LM339 on the pcb, but not on the schematic. What could it be used for?
This is still an open question and I'd like to know as well.

Recently they've discontinued the SMD version. Eventually they'll be more sought after than they already are. So I'd like to make some headway and do up an exact clone of the PCB. It'll be a hell of a project but I've done crazier things :lol: Also - I don't personally know anyone who has one of these so I can't reverse engineer it to get the dimensions and resolve the questions at hand. So this will take me a while to replicate.

I've still got my vero boards kicking around unfinished. So that's still something I can work on. I've attached that layout (from my previous post) to this one. I'm also working up a BOM to clone the original through-hole version entirely. So I'll at least have all of the parts aside for when the main board is ready. I'll share that for the sake of collaborative effort when it's sorted.

-KM
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OTAPHASER.png

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