THE Microbrute Modification thread

[HipDestroyer]

Hey guys


I'm a music tech diy newb but I'm really tempted to modify my wonderful, beloved MicroBrute and make it even more powerful.

I've seen a couple Micrbrute mods mentioned around the forum and the internet but not a whole lot of them. So, I thought I'd collect them here and ask whether you guys have experimented any more with modding the Microbrute?



The schematics
Are here: Here.

The Hack-a-MiniBrute thread
Is here.

Midi out mod
I would love to do this myself. Found this album by accident while googling – if anyone can decipher the images and let us (=idiots like me) know how to do it, please feel free to share it.
Midi out mod

VCA CV in
Yusynth has this mod on his hackabrute site. This could be useful – according to yusynths website this was made for a theremin to be used with the input but I imagine using the LFO out into this would make some sexy vibrato effect as well.
VCA CV IN

OSC waveform outputs
Flux touches on the subject of adding individual outputs for the waveforms in this really really helpful video (which is 99% about the Minibrute but I guess the technique can be applied to the Microbrute) by using testpoints TP93= SQUARE VCO, TP94 = SAW VCO, TP102 = SUB VCO, TP124 = TRIANGLE VCO.
[video][/video]

So yeah, please share your DIY experience with the Microbrute. As soon as I have tested some of the above, I'll add to the subject.

[abelovesfun]

I've been slacking on modding my brutes. Might start the micro mod tonight. My intention was/is to use a DIN connector/cable between the brutes and a stomp box enclosure. My main hesitation thus far has been dremelling the port for the din connector. Is there any disadvantage to building the buffer op-amp in the stomp-box enclosure vs within the brute? Seems simpler to me.

[HipDestroyer]

Just saw this on Reddit as well:

"What I added was individual wave output for each wave. The test points on the outermost PCB ( on the bottom) will give you direct way of outs but they are the waves without the nice modifications aka super saw, Metalizer, pulse width modulation, and the sub modification of one fifth tuning. I wanted those since they would be fairly intense and crazy when using them for filter frequency modulation control or FM. It was very simple to find them on the board where the potentiometers reside. All potentiometers do for amp is take a signal and ground and go between them. So one of the Pens is obviously a full level attenuated signal, and the other that outputs the wave is the attenuated signal so its just probing with the scope to find it. It took all of about 10 minutes then its figuring out where you have to solder to and from wire length, Jack physical placement and any physical modifications that need to happen and then testing circuit before you drill holes. Since on a new machine like this you're obviously voiding the warranty. Then it's getting it done correctly and precisely so there's no physical conflicts on reassembly, or shorting out because something presses or touches somewhere else that it should not."

"When I first did it I took the output directly from the wave mixer amount potentiometer after it was attenuated. This doesn't work very well since you must turn the wave up to get it to act as a frequency modulator and as an audio source. After initial tests I then had to add for 100k potentiometers, one for each wave. Then the wiper out of those potentiometers goes to your jack."

"It's a very tight fit inside. Small case and some physical fitness going with the Dremel tool had to happen. But nothing out of control. Luckily I had some very small low wattage potentiometers lying around that just made it by a millimeter or two inside the case."

[HipDestroyer]

Adding the pots to the wave outs is a nice touch!

[euromorcego]

interesting!

Midi out mod
I would love to do this myself. Found this album by accident while googling – if anyone can decipher the images and let us (=idiots like me) know how to do it, please feel free to share it.
Midi out mod

But it is written there, or?

Arturia Microbrute Midi Out mod
Yellow : DIN pin 5 on LPC2361 pin 82
Red : DIN pin 4 on 3.3V with 100R in serial
Black : DIN pin 2 on ground

Midi Out requires three connections: ground and 5V/3.3V and serial output. Pins 2, 4, 5 of the 5 pin Midi Jack. Maybe the serial output should be buffered?

[HipDestroyer]

interesting!

Midi out mod
I would love to do this myself. Found this album by accident while googling – if anyone can decipher the images and let us (=idiots like me) know how to do it, please feel free to share it.
Midi out mod

But it is written there, or?

Arturia Microbrute Midi Out mod
Yellow : DIN pin 5 on LPC2361 pin 82 (1)
Red : DIN pin 4 on 3.3V with 100R in serial (2)
Black : DIN pin 2 on ground

Midi Out requires three connections: ground and 5V/3.3V and serial output. Pins 2, 4, 5 of the 5 pin Midi Jack. Maybe the serial output should be buffered?

Sure, but there's a couple of things in there that are a bit hard to understand for a diy newb as myself.

1) This pin seems so tiny. Granted, I haven't opened the synth yet and seen for myself but it looks microscopic. How does one solder such a tiny pin without shorting the whole thing?

2) I'm not sure what "100R in serial" means – haha, yaeh, as I said, I'm a bit of a newb.

[HipDestroyer]

interesting!

Midi out mod
I would love to do this myself. Found this album by accident while googling – if anyone can decipher the images and let us (=idiots like me) know how to do it, please feel free to share it.
Midi out mod

But it is written there, or?

Arturia Microbrute Midi Out mod
Yellow : DIN pin 5 on LPC2361 pin 82 (1)
Red : DIN pin 4 on 3.3V with 100R in serial (2)
Black : DIN pin 2 on ground

Midi Out requires three connections: ground and 5V/3.3V and serial output. Pins 2, 4, 5 of the 5 pin Midi Jack. Maybe the serial output should be buffered?

Sure, but there's a couple of things in there that are a bit hard to understand for a diy newb as myself.

1) This pin seems so tiny. Granted, I haven't opened the synth yet and seen for myself but it looks microscopic. How does one solder such a tiny pin without shorting the whole thing?

2) I'm not sure what "100R in serial" means – haha, yaeh, as I said, I'm a bit of a newb.

And another thing I'm curious about regarding this midi mod is – do you think it would transmit midi cc as well or just the notes?

[HipDestroyer]

Also, a potentially important information I noticed on yusynth's sparse website:

"Rotary potentiometers: the best substitutes are those from the PTV112 series by Bourns (available at Mouser, Digikeys, farnell...)"

[HipDestroyer]

So. A quick update. I finally got around to doing some modifications.

And I have to say... It was pure NAM in there. Those test points are way smaller and way closer to other things than I had expected. This was even more daunting to me cause I'm still a newbie at soldering, but in the spirit of DIY i defied all common sense and went ahead with the soldering anyway. And seems to work!

To be begin with I only did the three waveform outputs as they are the most important mod for me: triangle (tp124), square(tp93), saw (tp94). The square output at tp93 is the hard one – it's only a couple of milimeters from a smt resistor.

Here are some pictures to boost morale

[sceledra]

That's acres of space! Nice job.

[HipDestroyer]

Okay, so I finally finished the first run of modifications and I'd like to share some important tips for other people who would like to do the same:

* Use a metal or plastic drill for drilling the jack socket holes in the side. Have a piece of wood behind the whole so it doesn't splinter. Use a tiny drill first, then slowly work your way up to the 6mm drill. IMPORTANT: Drill at low speed so you don't melt the plastic.

* Use a pointy canonical soldering tip for the test points - as I said, some of them are tiny and wedged inbetween some tiny ass SMT stuff.

* ALIGN THE HOLES. I didn't do this – I thought I did, but I didn't. So the holes are a bit out of line with eachother which isn't very sophisticated. So really take your time in aligning the holes before drilling.

* The sub out (at tp102) is modifyiable with the sub>fifth knob, FYI, as opposed to the three raw wave outputs that aren't affected by any pots.

* The triangle output (tp124) isn't as loud as the other outputs. I'm wondering what might cause this. Can anyone else who's done this mod confirm this? Maybe I have to throw in a opamp to fix this?

Here are some pictures of the thing. I might do a second run of mods – make the midi output, maybe try and find a BRUTE CV IN – that would be swell.



At first, (first hole on the left) I tried using a wood drill which almost messed up the whole thing (fortunately the nut from the jack socket covers the mess. All in all I can really recommend doing these mods – they take a wonderful instrument to the next level.

[HipDestroyer]

Oh and if anyone has an idea for how to screenprint either the waveform symbols or tiny text under the jacks that would be appreciated. I thought about this for a long time without coming up with a good diy solution

[Rex Coil 7]

Not the same kind of ~mods~ ... but ....



The initial chopper thread .... viewtopic.php?t=134893&highlight=

And another chop thread, this time it's the double chop .... viewtopic.php?t=136152&highlight=

Perhaps some of that helps motivate.

[cupwise]

so i'm guessing you could do some cool psuedo-feedbacky stuff now like use the raw waveforms to modulate the stuff in the mod matrix?

would the raw waveforms already be at appropriate levels to just patch them into euro modules?

seems like itd maybe be cool to have both the raw waveforms and the ones processed by the knob effects. vca cv in might be cool for being able to get some amp mod stuff in there. if lfo rate could be cv'd that might be cool too, and i agree the brute factor would be cool for cving (if possible).

[seanbonner]

You didn't by any chance take close up photos of where each of those soldering points were did you?

[BigCranberry]

I added a VCA CV input with an attenuator and a dedicated VCA control knob.

The CV input connects to a linear 10K pot which is used as a voltage divider. Pin 1 of the pot connects to one of ground pads on the rear board and the wiper connects to TP10 (any of TP10-TP14 will work) on the front board.

The VCA control uses a linear 10K pot as a voltage divider. The voltage source is TP56 on the rear board which is the +5VNUM rail. The wiper connects to TP11 on the front board.

The VCA control is really useful for setting an offset for the CV input.





I'm working on a dedicated clock inputs and outputs next. I will post details once those are finished!

[melittophily]

Look what someone (not me) shared on reddit today: PWM expansion mod!

I really need to sit down and practice on a scrap SMT board so I can get working on all this. If I get the VCO waveform outputs and VCA CV input working, I'd really love to complete it with a switch to turn off the internal keyboard/sequencer cv/gate to VCO/EG inputs, but it's probably beyond my skills in execution.

[Fwestivus]

I'm just debating getting one of these for having a tinker with, and notces in the schematics that there's a hard sync and soft sync input labelled - has anyone made use of these?
Any other interesting mods beyond what's already here?

[puffinstuf87]

I HAVE noticed the sync test points. Just got an MB, was browsing through the schematic because id really like to add a linear fm input, which i believe is possible, though id like it if someone would confirm my reasoning isnt nuts... The U17(b) opamp in the MB VCO schematic (its yusynth VCO counterpart would be U3b) would be attached to the Lin FM jack with a 100k resistor at the inverting input.

Anyone see a reason why that wouldn't work?!?

There's also a test point at the VCOs triangle shaper that could be tapped for a sine shaper as well, tho the voltage might need to be attenuated before going back into the line in. The thru zero pwm mod is interesting as well. Seems this thing is full of possibilities.

Edit: I'm not sure if its cool to post the MB schematics btw - OP posted the link

[neutronarmy]

I HAVE noticed the sync test points. Just got an MB, was browsing through the schematic because id really like to add a linear fm input, which i believe is possible, though id like it if someone would confirm my reasoning isnt nuts... The U17(b) opamp in the MB VCO schematic (its yusynth VCO counterpart would be U3b) would be attached to the Lin FM jack with a 100k resistor at the inverting input.

Anyone see a reason why that wouldn't work?!?

There's also a test point at the VCOs triangle shaper that could be tapped for a sine shaper as well, tho the voltage might need to be attenuated before going back into the line in. The thru zero pwm mod is interesting as well. Seems this thing is full of possibilities.

Edit: I'm not sure if its cool to post the MB schematics btw - OP posted the link

I noticed the same thing when comparing the Yusynth schematic to the Microbrute. I'm planning to break out several of the test points to the side panel - including the syncs and linear FM - and build an external passive attenuator box to avoid the space of internal pots. Currently I'm deciding what connector to use internally to allow the main PCBs to be removed easily without removing all of the additional jacks. If I end up completing the modification I'll let you know how it all goes.

[puffinstuf87]

The only thing thats throwing me is that it opamp input takes 12v in the MB and 5v in the yusynth

[Fwestivus]

Hard sync in works fine. Soft sync doesn't seem to (looks like there's a cap missing, but even with it in, it doesn't seem to do anything). Here's sync in -
[video]https://scontent-lhr3-1.cdninstagram.co ... 4624_n.mp4[/video]

[neutronarmy]

Hard sync in works fine. Soft sync doesn't seem to (looks like there's a cap missing, but even with it in, it doesn't seem to do anything). Here's sync in -
[video]https://scontent-lhr3-1.cdninstagram.co ... 4624_n.mp4[/video]

Embedding Instagram that way doesn't seem to work. I assume this is the video you were sharing:

I also noticed from your page that you have done a whole host of mods - you listed a few here: Great work! Very inspirational in the extent you've really gone all out.

I was curious about a few modifications you mentioned. I'll just list the questions for less confusion.

1). Perhaps I am being dense, but doesn't the VCF already have a CV input? Are you running a second in parallel?
2). Am I correct in assuming you tapped the VCF before the mix at TP19 to be able to use the filter standalone?
3). Do you have a preferred LFO that was small enough to mount internally, or did you whip something up protoboard?
4). What are the additional switch and the pots towards the top of the unit?

So much interesting stuff. Thanks again for sharing!

[Fwestivus]

Sorry for taking a while to get back on this!

The mods (so far) are:
Seperate VCO wave outs, after shapers
Mod wheel CV out
Pitch CV with glide out
VCA in (with a pot)
VCF in (with a pot)
VCF out
Sync in (with a switch for hard/soft)
A little tri/quare lfo with a switch for fast/slow and a pot, and that's normalled to the extra VCF input
An extra audio in
MIDI out

All the ins and outs are buffered, and so far I've had no magic smoke!

It's a really fun synth to mod - the schematics and all those test points make it easy (and easy to go a bit overboard...) and the plastic case means drilling holes isn't too much of a pain.

There's a fair bit of room under the keyboard, so at some point I might see if I can squeeze a simple VCO in or something...

Hope that helps!

[RingMad]

I can't delete this post. Please disregard it. I edited it so I can put this notice here and not waste anyone's time. I finally realized my stupid mistake and do not need help on this now.

original post:
Can anyone who did the MicroBrute CV in for VCA mod help me?

I did the mod for a friend, and it is pretty simple, but it doesn't seem to work. I am expecting that the volume would go up and down according to the voltage (more voltage = more volume). I press a key, vary the CV I'm sending, but there's no volume change.

Are my expectations incorrect? Do things have to be set a certain way in order for the CV to have an effect? (I've tried various combinations -- especially the one that Coralie Ehinger shows in her video controlling her MicroBrute with a Theremin (as mentioned on the hackabrute page, and which is VCA on Env, Env Amt pot at full, and all ADSR sliders up).

I have been doing electronics for several years, know how to solder, and have built many projects (mostly audio, but not quite modular synth). I admit to not being well-versed in using voltage-controlled synths, but I understand the concepts.

The VCA still works like it did before the mod, so I am confident that I didn't fry anything when doing the mod.

I usually work in single supply, but I tried with my friend's synth (Kilpatrick Audio PHENOL) with the LFO that produces -5V to +5V. I also tried with my homemade sequencer which produces a CV out from 0 to 10V, with a pot that can attenuate the max down to 5V. And I tried with a simple voltage divider made using a potentiometer to give 0 to 9V. I also tried with the Brute's own LFO out. Nothing varies the volume of the Brute.

Thanks for any advice,
.:James:.