Help building the 70's Maestro MPF-1

[Dirk_Hendrik]

According to a page at Angela Instruments ( http://www.angela.com/catalog/potentiometers/Alps_Pots.html ), S-taper is the same as linear taper.

That's not completely true although a linear will do the trick.
The S-taper is the same as the "w" taper found in the tubescreamer for the tone control. It's also referred to as the "g" taper and is a combination of a log and a reverse log travel. This makes the tonecontrol "nicer" to control.

example (partially borrowed from R.G.)

[Rectangular]

I'm totally in favour of this thread

I've got one of these gems and have wanted to clone a backup for a long time.

your main hurdle is that is uses old hard-to-find OTAs and other semi-obscure chips, so sourcing those at a decent price will be tricky.  OR we could work on modifying the circuit to use more common equivalents (lm13600s for example)

also an idea for a modification/improvement: when you switch the unit into overdrive mode, there is a considerable volume drop,  rectifying that would be nice. 

btw: the schematic jpg isn't showing up

[Rectangular]

actually maybe I'm confusing this with the maestro phasors,  I can't remember if this actually uses any OTAs. its such a hassle to disassemble these cases,  so kudos to Theehman for taking the time to do so.

still can't seem to find a schematic anywhere on the net (without having to pay for one)

[theehman]

actually maybe I'm confusing this with the maestro phasors,  I can't remember if this actually uses any OTAs. its such a hassle to disassemble these cases,  so kudos to Theehman for taking the time to do so.

still can't seem to find a schematic anywhere on the net (without having to pay for one)

Let me see what I can do.

[theehman]

actually maybe I'm confusing this with the maestro phasors,  I can't remember if this actually uses any OTAs. its such a hassle to disassemble these cases,  so kudos to Theehman for taking the time to do so.

still can't seem to find a schematic anywhere on the net (without having to pay for one)

Not the greatest, but if there's any questions, let me know.

[fuzzo]

That will be  really  cool if you can  make a usable layout of that pedal !  (To calm dowm my QOSTA's fan attitude )

The first IC reminds me something . I believe a guy here I've made a similar distorsion unit.

[slacker]

The first IC reminds me something . I believe a guy here I've made a similar distorsion unit.

Yeah it's a CD4007, basically a bunch of Mosfets on a chip. There's a few distortion designs using it.

Here's the schematic that was linked to in the first post in the thread, I downloaded it ages ago, but I've never got round to doing anything with it. If anyone has a problem with me posting it let me know and I'll remove it

[MarcoMike]

well... it seems it is possible to substitute the whole CD4011-4016-rotaryswitch with just 4 spdt switches... also I'm not sure the second part of the rotary is doing anything at all with those 330 ohm at some positions...

[fuzzo]

An another cool thing will be creating another pedal inspired by that Meastro but with a different schematic, more "modern" (I don't really know how that could be more "modern").

I don't know if it's mentioned somewhere in that thread but that pedal (and other with the same enclosure) have made by Moog.

[Rectangular]

thanks for the two schematics guys, great stuff

the TL022 is the only thing I'd have to order. I forget what the deal with those is, are they like the tl082s where its some impedance difference (compared to a tl072, 074) ? or they're extra precision ?


man, what a weird pedal, this isn't the kind of circuit I was expecting at all, after looking at the other maestro designs.

[gigimarga]

I hope that I will have some time to make a PCB for it next weeks 

[gigimarga]

 

[fuzzo]

I hope too 

[gigimarga]

I have a lot to work at my job, so, maybe, the next month I will have sometime for MPF

[fuzzo]

Isn't to press you, take you time. I say that just to mention the fact I'm intersting too (but I haven't the skills to do PCB of a big project like that)

Anyway, Someones can explain how works that circuit , the different part which act on the signal.

[SpencerPedals]

I have a fair amount of time during the week, lately.  I was thinking about starting a PCB for this in Eagle, as I've done a few with success.  This, however, is one bizarre looking creature and I can't say I quite understand what is going on in some parts of it.  I would be willing to collaborate by doing the normal-looking things in the circuit, if someone with Eagle experience and a knowledge of the circuit would be willing to tie up the bizarre switching and the weird intricacies like that.  I have no problem with the average or even complex fuzz box, but this one is out of my league.  I can certainly lay groundwork, though.  Send me a PM if you're interested.

[Rectangular]

I agree, the switch arrangement is very confusing.  nothing is more frustrating than trying to decode someone's  "A,B,C,D,E,F" labeled connection points and hoping you're doing it correctly.  rotary switches can confound even the simplest of schematics.

[jmasciswannabe]

I am going to be on a plane the majority of Sunday and Monday. If Theehman can send me a picture of the trace side I would gladly put together the original layout. I've no experience in designing my own or using eagle or anything like that, but maybe an original layout can be some groundwork for a more advanced version. Especially if nelson takes a swing at it!

[Dirk_Hendrik]

http://www.dirk-hendrik.com/temp/mpf_track.jpg
http://www.dirk-hendrik.com/temp/mpf_comp.jpg

[jmasciswannabe]

Cool...I'm on it! I'll report back Tuesday.