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 Forum index » DIY Hardware and Software » YuSynth
Minibrute schematics vs Yusynth + some potential mods
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radray



Joined: Sep 21, 2014
Posts: 3
Location: United States

PostPosted: Thu Oct 02, 2014 9:45 pm    Post subject: Minibrute schematics vs Yusynth + some potential mods Reply with quote  Mark this post and the followings unread

This topic is for the folks who love reading synth schematics and for those looking for some mods for the Minibrute.

I found out last week that the Minibrute schematics website by Yves Usson is up and running http://hackabrute.yusynth.net/index_en.php. I immediately began reading all the pages, looking for patch points and finding out how the heck the Sub oscillator works. Then I began going page by page comparing schematics with Yusynth designs to see what may be different. Most areas have some subtle changes others are drastic.

Super Saw/Saw Animator-
Some Yusynth modders may notice the Super Saw/Saw Animator has the triangle to sine mod for the lfo as seen here http://electro-music.com/forum/topic-18854.html. It's pretty noticeable when using the Yusynth module next to the Minibrute. The Minibrute Super Saw is a much smoother LFO to the stock Saw Animator.

Metalizer/Wavefolder-
The most obvious change is the Metalizer. I expected as did many on the web that it would be the same as the Yusynth Wavefolder but to my not so smart eyes it looks more like a CGS29 Wave Multiplier using transistors instead of diodes. If you can break this circuit down or link to where it has been used please speak up. I have to guess and suppose that the use of a different circuit is because Jürgen Haible designed the circuit in the Yusynth module.

Something I didn't expect to see was Velocity CV being used to control the depth of Envelope 1 with an OTA. I didn't think there was Velocity CV implemented in the Minibrute. I have never noticed any change in depth before but it's there so maybe simpler patches will show it off. I intend on probing it to see how much range is there in the hopes of adding a velocity CV output. And now that I think of it how the heck could that work since the envelope has to decay after a key is released. Hmmm probing should give some answers.

Another thing that I was surprised to see was the use of TRS jacks on the CV in's with the ring connected to +12V through a 10k current limiting resistor. So this means you can use an expression pedal or volume pedal to control those inputs not just a CV pedal as many have thought. Why the heck the manual doesn't mention this I have no idea. I tested it out with a multimeter and sure enough just under +12V is on the ring. Then I used an Ernie Ball Jr. volume pedal and a 3.5mm trs to mono left right splitter to test it out. Of course with a 12 octave range the pitch input can go beyond human hearing but the filter and VCA inputs were very usable. You could rig something up to drop the voltage a bit for the pitch but for the VCA it felt like the full range of the pedal was used.

One other neat thing according to the schematic is that there is already traces set up for soft and hard sync connections to the VCO. Sweet! Should be simple to add an input port for syncing to external VCO's.

Well I'd love to hear other folks thoughts on this sweet gift from Yves and Arturia and some kind of description of the Metalizer circuit.
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a100user



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PostPosted: Thu Oct 02, 2014 11:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice work

I'll be watching this space Smile

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radray



Joined: Sep 21, 2014
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PostPosted: Thu Oct 09, 2014 7:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

So I did a bit of probing last night just checked out spots for tapping Aftertouch CV, Mod Wheel CV and Velocity CV signals. I found that the Leafcutter mod points for Mod Wheel "PT655" and Aftertouch "PT656" found here http://leafcutterjohn.com/?p=1887 are pre processor and only get around 1 volt of CV max so I tested the post processor points Aftertouch "PT676" and Mod Wheel "PT674" and got about a 0-10v CV range so I would recommend using these points for Mod and After Touch over the Leafcutter ones. Since the After Touch is post processor it's response will of course follow the software settings of lin, log and anti.

Now for the Velocity CV results. In order for the Velocity CV to have an effect on Envelope 1 output depth while letting Envelope 1 decay after a note is released the Velocity CV will hold it's value until the next note is played. The softest key press gives a reading of 8.5v and the hardest (or quickest) key press gives a reading of 9.5v. Not a whole lot of range + that's a high offset. So if I end up using the Velocity CV I'll have to set up a circuit to subtract 8.5v followed by a gain stage to get it to a 0-10v range. Could be worth it.

That's it for today stay tuned for more results and I'm still interested in a description/analysis of the Metalizer circuit.
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yusynth



Joined: Nov 24, 2005
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PostPosted: Tue Oct 14, 2014 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes velocity was part of the initial specs in the MiniBrute, but as it is implemented in the MiniBrute it does not give an interesting result therefore it was decided to remove it from the list of official features rather than providing something that was not really OK. As a matter of fact we had no time t o solve this with respect to the deadlines.
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yusynth



Joined: Nov 24, 2005
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PostPosted: Tue Oct 14, 2014 4:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Concerning the Metalizer (a yusynth Module will be soon published on my site) you are right concerning the fact I didn't use JH design for reasons of intellectual properties. I designed the metalizer by chaining basic cells similar to CGS52.
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yusynth



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PostPosted: Tue Oct 14, 2014 4:40 am    Post subject: Reply with quote  Mark this post and the followings unread

By the way if you design some nice hacking I'll be pleased to publish it on hackabrute.
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radray



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PostPosted: Fri Oct 17, 2014 9:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you for the feedback Yves. I totally missed the "Simple Wave Multiplier" and it's even on the schematic for CGS29. head banging monitor The only info I can find on this circuit is at http://www.tradeofic.com/Circuit/3560-NONSELECTIVE_FREQUENCY_TRIPLER_USES_TRANSISTOR_SATURATION_CHARACTERISTICS.html I don't know if there was more in the article from Electronics Design. Seems to be used in some DIY guitar fuzz pedals as well.

This weekend I will be doing some probing around the LFO and Sub-Oscillator. Curious about the "CMD PWM" from the processor. Is it a compensation control for various speeds or some never utilized PWM processor control. For the Sub-Oscillator I will be using an audio probe to see what PT151 and PT152 sound like.
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