Musitronics - Mutron III 1975 factory schematic

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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modman
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Post by modman »

Check out JC's page on this one - also contains the original schematic as well as some in depth discussion:

http://www.lynx.bc.ca/~jc/pedalsMutronIII.html
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Post by modman »

modman wrote:Check out JC's page on this one - also contains the original schematic as well as some in depth discussion:

http://www.lynx.bc.ca/~jc/pedalsMutronIII.html
The original source of this schematic hosts a larger version, I think
http://home.houston.rr.com/cjlectronics ... utron3.jpg
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Torchy

Post by Torchy »

Full DIY-ed project with links to RG/GGG pcb and layout etc...

http://www.pisotones.com/MuTron-III/MuTronIII.htm

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Post by remork »

hi there
been reading a lot round here
major source of learning.. thanks

i am scratching my head trying to get an old Melos Effectmatic (= mutron III clone, minus few minor details) to work, with varying success..
before any other troubleshooting can take place, i have a question about powering the thing :oops:
should it be possible to drive it from an 18v voltage divider circuit, to get the + and -9v? >>

+18v----- +9v
I
I
>
>R1
>
I
I---------GND
I
>
>R2
>
I
I---------- -9v
-

i tried, with diff res values (R1=R2), and i got some strange results.. 12v to 6v, 15v to 3v..
could this have anything to do with the diode driver bias circuit- another volt divider between +9v and gnd?
i will try to run it off two batteries tomorrow to see how that works out.
i will have to stock up on batteries anyway, but i really want to be able to run it off an adapter if it ever comes back to life in a decent way.. any thoughts?

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Post by R.G. »

It's not practical to do it that way.

A resistor voltage divider passes some current through the two resistors to cause the voltage division. If you then have current pulled out of (or pushed into)the middle of the divider, then the voltages cannot any longer be balanced as they will have unequal currents. For a divider to work with any accuracy, the current through the two resistors must be at least ten times the current entering or leaving the middle point. For powering an effect, that's a prohibitive amount of current.

Try using a charge pump voltage inverter like the MAX1044 or LT1044/1054 to make -9V from +9V, as in the article at GEO (http://www.geofex.com) under circuit sweepings.

remork
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Post by remork »

thanks!!
had a feeling it might be a tad more complicated
rookies, gotta love us.. :oops:

just had a look, seems pretty straightforward, great explanation as well!

don't mean to hijack the thread, but..
so far i've only used the ICL7660S as a voltage doubler, could i use that one as well?
it's just that i know where to get them here, and it also has the frequency boost.

thanks again!

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Post by DiscoFreq »

remork wrote:i am scratching my head trying to get an old Melos Effectmatic (= mutron III clone, minus few minor details) to work, with varying success..
I have some of these (Effectmatics and Funky Filters), if you need pictures or other info (from someone who still has to learn about electronics ;))...

I burned the first Melos Funky Filter I received (4-5 years ago) by connecting a 1000mA Boss adapter to it (it worked with batteries but not with a smaller adapter): it has the same plugs but it turned out to be inverse polarity ;)

The guy who repaired it said some of the battery wires were wrong, but it worked with batteries, so he was probably confused by those 9v/18v things somewhere :)
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Post by Bernardduur »

I had one in the shop a long time ago! The batteries are in parrallel so they won't deliver 18V but simply 9V

I have a schematic of it somewhere!

Schematic
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remork
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Post by remork »

thanx for that schematic!!
could try to run photoshop over a mutron schematic highlighting the differences-
not that that would be any use to anyone. if you're gonna build one, might as well build the mutron..?
Bernardduur wrote:I had one in the shop a long time ago! The batteries are in parrallel so they won't deliver 18V but simply 9V


you mean i can basically run this thing off a 9v supply? :scratch:
oh man :slap:
i'll give that a whirl one of these days!
i put it aside for the moment. (was focusing on the elka dizzytone..)
but i can see why someone would be confused by those battery wire hookups- i know i was..

thing is, i don't even like it on guitar- i want to use it on a casio toy piano. don't ask :roll:
thanks guys!
i'll try not to fry mine :wink:

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Post by JiM »

Bernardduur wrote:Schematic
Interesting schem, it almost gives an answer to a question i think about for a while ...

In a lot of pedals (phasers, compressors, envelope filters, ...), variable resistance is acheived using vactrols/optoisolators/LED-and-LDR or JFETs. What about using an optocoupler (LED and phototransistor) for that purpose ?

This Melos Effectmatic shows me it is indeed possible !

I happen to have a pile of CNX48 photodarlington-couplers http://www.datasheetcatalog.com/datashe ... X48U.shtml , which would be easier to use than heat-shrink-tubing LEDs and LDRs or getting NOS vactrols ...
These are made for digital signals, but aren't CD4049 too ?

I can even imagine a LFO-controlled gain in a Bazz Fuss :mrgreen:

PS : dear moderators, please move this post if it's too much off-topic.

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Post by Bernardduur »

Could someone provide me with a picture of an original Mutron III? I'm currently writing an article for a magazine I work for about the Mutron III but I lended out my own and now I can't make any product pictures........
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Bernardduur
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Post by Bernardduur »

Good idea!
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