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x0x mods to MAM MB33 mkII???
Moderators: Altitude, adafruit_support_bill, adafruit, phono, mome rath

x0x mods to MAM MB33 mkII???

by human fly on Sat Feb 19, 2011 8:26 am

any thoughts about modding a MB33 MKII with x0xbox parts?
it is supposed to be a faithful copy, using cheaper components.
schematics are around, partslist too, i think.
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Re: x0x mods to MAM MB33 mkII???

by guest on Sat Feb 19, 2011 2:54 pm

it doenst seem like there is much in common
between the mb33 and the x0x
the only place where parts could swap
would be in the filter
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Re: x0x mods to MAM MB33 mkII???

by human fly on Sat Feb 19, 2011 7:21 pm

ah right. and i wrote 'faithful copy' which it isn't; it's just that i read some
manufacturer thing where they said they'd copied it. evidently not so, then.

saw the filter looked like a diode ladder, hence the question.

it isn't a bad little unit at all-and maybe the filter could be improved in
this way. seem to remember it didn't quite get there, and the overall sound
was a bit harsh.

not necessarily to make it 'pure 303', but maybe give it a bit more range using
some of the tricks used here, if there are any 'obvious' weak points.
other points:
there are a couple of mods to FM and resonance online; and i've wondered about
trying to get longer keyed notes(the decay is set and cuts off)..i mean, i have a
x0x now, so i thought something slightly different and complementary.
it has a sub osc, and pulse/saw can be mixed, and there's-i think- PWM.
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Re: x0x mods to MAM MB33 mkII???

by human fly on Tue Feb 22, 2011 9:05 am

so... do you think it'd be worth having a go at changing over
filter parts, and where would be a good place to start?
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Re: x0x mods to MAM MB33 mkII???

by altitude on Tue Feb 22, 2011 12:32 pm

You're making a huge assumption that the MB33 is laid out anything like a 303/x0x. Without proper schematics, you are wasting your time.

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Re: x0x mods to MAM MB33 mkII???

by human fly on Thu Feb 24, 2011 4:09 pm

http://www.box.net/shared/xputk0bgzk

here's a set of schematics found the other day.

the filter section looks very familiar. but i really don't
have the experience/skills/knowledge at this stage, and
ask out of curiosity. it's a decent little unit that could do
more, has midi cc control, etc. thinking it could be expanded
to be something other than a 303? has sub-osc, pwm..

there might be more info somewhere, parts, etc.
thanks for any time, info, interest, etc.
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Re: x0x mods to MAM MB33 mkII???

by altitude on Thu Feb 24, 2011 4:34 pm

hey, nice find.. Might have to clone that sub osc..

Any chance at some readable ones though?

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Re: x0x mods to MAM MB33 mkII???

by Brassteacher on Thu Feb 24, 2011 6:59 pm

While the filter is a fairly accurate copy electronically, it is built with CA3046 chips and only a few discrete transistors. It's a decent design, and switching C2291 and C1583 in place of the CA3046 chips is not only likely to make no audible difference. However it is highly likely to drive the experimenter INSANE trying to fit the individual transistors in the holes correctly, especially trying to figure out which four holes will be left empty.

Put it this way, yes, I could do it, but I wouldn't. I don't have so much hair left on the very top of my head that the amount I'd pull out in the process wouldn't show... ...especially since it will sound the same after all that work.
Don Taylor, a.k.a. Brassteacher
"Jack of all trades, master of none, proficient at even fewer..."
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Re: x0x mods to MAM MB33 mkII???

by human fly on Fri Feb 25, 2011 2:32 pm

haw haw..
so you're saying the CA3046's replace transistors, and it'd be a major pain
to transfer/replace these within same location?
so, getting somewhere, anyway. thanks for having a look.

altitude, i have better copies if these weren't good, i'll dig them out.
(may be more infos there too)

not quitting on this yet, though :) since this thing does deserve some
thought, i reckon: it's still a pretty good little monosynth, and it's analogue,
and has potential for mods, whatever they could be.
(for the sake of argument...)

x0x mods are very specific, seeking to emulate a specific device exactly.
this doesn't have to be about that. (you can mash out perfectly good acid with
an ms10, really. bit darker though...)

ok: so i thought it might be fun to be able to oct/detune the osc+sub, that it
might be fun to add an lfo to modulate pwm(?), and that something could be
done about the eg decay on notes (currently it can't hold a note longer than
preset decay if playing it keyed-eg: no sustain). i also remember not being
totally happy with the slide action, so i don't know if it resembles 303/x0x.
(you have to do the overlapping notes thing).

other than that, the filter lacked something. sorry, i know it's a long wishlist,
but that's the cat out of the bag anyway. cheerz.
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Re: x0x mods to MAM MB33 mkII???

by altitude on Fri Feb 25, 2011 2:55 pm

Please find better copies, the sub osc and PWM on the MAM box were two things I really liked about it and ive been looking for those for a while

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Re: x0x mods to MAM MB33 mkII???

by Brassteacher on Fri Feb 25, 2011 3:37 pm

human fly wrote:haw haw..
so you're saying the CA3046's replace transistors, and it'd be a major pain
to transfer/replace these within same location?
so, getting somewhere, anyway. thanks for having a look.

other than that, the filter lacked something. sorry, i know it's a long wishlist,
but that's the cat out of the bag anyway. cheerz.


Now, given you've said above, changing the filter to be a TB-303 filter would be a pain. However, changing it into a Moog transistor ladder filter would be EASY. The board layout would be nearly identical, as most later Moog factory filter builds used CA3046 for the top and the bottom of the ladder.

If you want to try it, let me know, and I'll write up a set of instructions.
Don Taylor, a.k.a. Brassteacher
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Re: x0x mods to MAM MB33 mkII???

by darffader on Sun Feb 27, 2011 11:42 am

While you're at it, if you have MAM MB 33 mkI schematics please post them too :D
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Re: x0x mods to MAM MB33 mkII???

by human fly on Sat Mar 05, 2011 3:46 pm

;p

mb33 mkII schemz, can't recall where from, but these are readable.

http://www.box.net/shared/jg30qnp3ue

not up forever, so grab them now, Interested Parties.
also, if interested, this, schem of mc202 audio(idem):

http://www.box.net/shared/rrl2ixvsrc

so, it looks like transistors are replaced by ca3046 ic's?
(is this anything to do with midi cc control?)

@brassteacher: could the moog mod be switchable, to keep orig
18dB/oct filter? there's a 'res' boost' mod for it that allows filter
to self oscillate; is this the same?

i read that this unit is 'poorly manufactured' and that solder pads are
prones to lifting, it's fragile etc.
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Re: x0x mods to MAM MB33 mkII???

by Brassteacher on Sat Mar 05, 2011 3:56 pm

human fly wrote:;p

so, it looks like transistors are replaced by ca3046 ic's?
(is this anything to do with midi cc control?)


No, mostly economy, one chip replaces 5 transistors, and they happen to be pretty well matched, plus one pair is connected as a differential amp already.

human fly wrote:@brassteacher: could the moog mod be switchable, to keep orig
18dB/oct filter? there's a 'res' boost' mod for it that allows filter
to self oscillate; is this the same?


No, the only way to do that would be to build the Moog filter on a daughter card and put a switch between the two. A properly built and calibrated Moog filter can indeed self oscillate, not sure what to do for the original filter, I haven't looked at the schematics yet.

human fly wrote:i read that this unit is 'poorly manufactured' and that solder pads are
prones to lifting, it's fragile etc.


Even "well manufactured" boards are prone to solder pads lifting, especially if they are double-sided with through-plated holes. Those take longer to heat enough to melt solder. It's safer to use solder wick on a double-sided board, and I use a solder-sucker on single-sided ones.
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Re: x0x mods to MAM MB33 mkII???

by altitude on Sat Mar 05, 2011 4:37 pm

Thanks HF! cloning the sub osc on that thing is definitely getting on the to do list.

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