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arturia minibrute modding

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

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codemode
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Post by codemode »

now that the schematics have been released maybe people can get on more with modding. I'm going to share these pics from when I did a benchmark of the Minibrute and documented the schematics a year or so back. They may be helpful to someone...

Minibrute

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bartleby
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Post by bartleby »

codemode
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Post by codemode »

very well I see they released everything including the pdf's of the pcb layout. I'll leave the pics up but recommend the Yusynth files or visually improved versions linked above.
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okelk
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Post by okelk »

Does anybody now a parts number/manufacturer of the 3 way switches used in the mini/microbrute? or a switch that has the same footprint?
..I managed to break the lfo switch on my microbrute....
codemode
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Post by codemode »

okelk wrote:Does anybody now a parts number/manufacturer of the 3 way switches used in the mini/microbrute? .
It would generally be hard to find a switch with the exact specs since the shaft length etc.. would be spec'd for the Minibrute, and distributors don't usually stock all variations of each part.
They probably source them from Wealth Metal, Chun Kai, or one of the many other Chinese companies making these standard switches.
  • Mouser has some from Alcoswitch such as the link below. You may get lucky w/ correct spec..
    http://www.mouser.com/ProductDetail/TE- ... arnGisA%3d
  • If you wanted to be disingenuous you could always pose as a company and order a few samples from one of the many suppliers that make them.
  • Worst case I'm sure you can buy one from Arturia (although their support doesn't seem to be very responsive)
artgiles
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Post by artgiles »

I would contact Arturia to request the part number and ask if they could sell you one. I have done this for switches for Presonus and Danelectro gear and both of them just asked for my address and shipped it to me for free (Presonus sent spares). :hyper:
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Shoggoth
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Post by Shoggoth »

One mod not mentioned on the Yusynth site:

The brute has some tuning issues in the upper registers that the manufacturer has implied was due to a component value mistake (R89). I saw on the Arturia forums one member upped R89 on his unit from the stock value (63.4k) to 390K and it worked well for tracking.

I just made the same mod (and I was terrified, not having much SMT experience or really the greatest soldering iron) and I can say it does help. The mod dropped the general tuning of the synth by a few notes, but you can easily fix that by working with the offset trimmer. As for a plastic handled screwdriver, I just wrapped my metal screwdriver handle in electric tape.

Unfortunately, no matter what you do, you can't get the full key range to be in tune consistently. I would highly recommend the mod though, the upper range was pretty much unusable otherwise imo.
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Flux302
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Post by Flux302 »

as pointed out in another thread... I had missed the post that had leaf cutter johns mods documentation lol... so I ended up doing it myself independent of his stuff. I haven't had a chance to read his mods yet but hopefully will later today. anyway, I did a video of my mods and how I got to em.
I am sure I am far less skilled than he... But this may help someone :)
[video][/video]
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FluxWithIt.com
Youtube.com/Flux302
The SynthSummitShow (Live show)
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Shoggoth
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Post by Shoggoth »

I did the leafcutter mods but was able to do it without the breakout box. I even added an attenuverter that's normaled to the filter env. I also added a hard/soft sync input with a switch but for some reason the soft sync isn't working (should be a simple fix). Im really happy about how it turned out, because I agonized over how to do the breakout box since I have zero space for any other equipment. The Tayda jacks fit nicely in the width of the side cheeks, though you need to use a slightly larger bit to create a larger opening on the interior after drilling the initial hole to allow the jack threads enough room to screw on the nut.

I'm surprised there hasn't been more activity in this thread after the full schematics were released.

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quietchannel
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MiniBrute mods!!

Post by quietchannel »

I love the dedication to the MiniBrute on MuffWiggler! I have a few questions that I hope some folks may be able to answer!

First-- The Pitch is very sensitive to the LFO +/- pot, to the Mod Wheel Vibrato, and to the Aftertouch Vibrato.
I usually want a very slight vibrato, but can never seem to achieve it.

Is there someplace where I could alter the circuit to reduce the minimum CV effect?

Second-- I want to sometimes use an external VCF or SVF. (Actually, I have built several from your website!)

Is it possible/easy to route the audio to/from an external filter, as well as the CV bus for filter cutoff control?

Thank you all very much!
Flynn
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Post by Flynn »

Thanx a lot Leafcutter for the documentation!
Saved us so much time!!!
You´re awesome!
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kites
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Post by kites »

Sweet brute mods up in here! Thinking of better was to incorporate my Minibrute SE. Right now, the poor thing is feeling alienated since my merging of modular.

Has anyone seen and good minibrute cheek/case mods incorporated into their modules?
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spacedog
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Post by spacedog »

Flux302 wrote:as pointed out in another thread... I had missed the post that had leaf cutter johns mods documentation lol... so I ended up doing it myself independent of his stuff. I haven't had a chance to read his mods yet but hopefully will later today. anyway, I did a video of my mods and how I got to em.
I am sure I am far less skilled than he... But this may help someone :)
[video][/video]
Thanks Flux302!

There is a Microbrute-mod for individual OSC outputs in the video above...

And another Microbrute-mod for VCA-CV input can be found here:
http://hackabrute.yusynth.net/index_en.php?&arg=6

Just saw them, have NOT done them...

:guinness:
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kites
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Post by kites »

@space ah thanks, those mods look great but scary to me. It's may be too advance for me at this point.

I guess I'm thinking of external mods as far as permanently incorporating a Minibrute into one's system / case. Didn't find much in the pics of setups thread.
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felixer
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Post by felixer »

Kitesrfun1 wrote:those mods look great but scary to me. It's may be too advance for me at this point.
maybe find some tech to do 'm for you? might cost a few quid but then you're avoiding any risks :mrgreen:
don't need midi, don't need keys, just want knobs and cables (all together now ;-)
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bitflip
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Post by bitflip »

There's one thing about the microbrute that's driving me nuts and would love to know if there's a straightforward way to "fix" it...

The LFO ramp wave (reverse ramp actually) begins its cycle halfway down the ramp instead of at the top, thus preventing a full-range sweep until a half-range sweep is completed.(!) :despair:

I'm sure there's a reason for this and i'll have to do some homework to figure out why, and how it might be fixed... though i lack a scope and much know-how. Anyone already tackled this "feature"? :help:
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LudfisterSound
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Post by LudfisterSound »

Just put together a PCB layout for all the buffered outputs and clock input listed in the Leafcutter document and the Vibrato range selection from the Yusynth Hack-a-Brute page. I'm not great at layout but it should work if anyone cares to verify it.
Attachments
MegaBrute PCB.pdf
MegaBrute PCB
(72 KiB) Downloaded 121 times
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sam
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Post by sam »

Thanks ludfistersound, helps me visualize the thing.
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Bamboombaps
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Post by Bamboombaps »

ive been offered a minibrute with a 'fried cpu board' ive not seen it in person yet but does this sound like its worth looking at? what is there thats irreplaceable?
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davestrength
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Post by davestrength »

Get it. If you can fix it cool. If not, I'll buy it from you. I need another dead one for test fitting panels on.
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Bamboombaps
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Post by Bamboombaps »

:tu:
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Troubleshooter
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Post by Troubleshooter »

I have put some resistors around that LFO pitch modulation pot.

I found it almosn impossible to dial in suble modulation.
bafonso
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minibrute with low volume problem

Post by bafonso »

Hi everyone,

I was looking into modding my minibrute but just recently an issue came up where the output is very low, both in headphones and main out. I opened it up and did some measurements and I'm wondering if you guys can help me debug this issue. I don't think Arturia can help me with this one out... (but let's not get into that)

Here's what I know and I'd appreciate if I could get some readings from a normally working minibrute. I initially thought the issue would be at the VCA out, but when I measured the PT40, at the envelope out, I get signals up to +6V if set a curve with attack and release. I'm guessing this is roughly normal signal? The reason I thought the issue would be the VCA output is that if I set the LFO to modulate the VCA I can get the VCA to open up much more but still not as loud as I remember. This leads me to believe the issue is in the VCA circuit and maybe the U17 opamp? The ratios are different between the LFO and the Env2 inputs into the opamp but I did not measure the LFO signal.

Then I thought, the issue is likely how the envelope out controls the VCA. So I look at R237100K and the same signal is there. After the resistor I get ~0V which I believe is expected for this opamp configuration but if I recall correctly I get 0V at the pin out of the Opamp U17B, which seems strange. I guess it should be reducing the voltage since the ratios are 22k/100k, does this make sense? I will read again tonight the voltages to see if I'm seeing a ~20% reduction.

I measured also PT50, where I should see a 2Vpp max but I'm getting only about 10% of that, which seems to indicate the issue with the volume happens before this. PT52 also reads very low.

I'm wondering if someone has some ideas to debug this issue and could tell me the values they're seeing on PT84, PT85 (mine is quite low here). Any help would be appreciated :)
bafonso
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Post by bafonso »

As it turns out, I found out that it looks like it is the filter type knob selector like many others. That would explain the weird Filter out value... Anyway, I've ordered the part that I saw mentioned in arturia's forum:

http://www.mouser.com/Search/ProductDet ... 1712F-24NS

Let's hope that fixes it :)
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davestrength
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Post by davestrength »

Thanks for this part number! Got a brute here with a bad filter select switch I've been meaning to look up.
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