Turning a Musini into a Midi Controlled Synth

[theshame]

Circuit Bent Musini Pt. 3 - Midi-controlled Synth

I love the Musini, and while I was bending a new one, I discovered that it uses a synth on chip for digital audio. The chip uses one pin for midi data. Turns out you can make some simple modifications to send midi into the chip and play it with a midi controller. I'll post pics soon, but the mod is simple:

1. Take your midi out ground pin to the pin labeled ground on the Musini's cartridge slot.
2. Cut the midi wire coming from the cartridge slot.
3. Take the midi out current source pin to the wire you just cut (the end that connects to the main board).
4. Play some notes on your midi controller.

It helps to turn the sensitivity on the Musini all the way down so you don't mix in the built in signals. If you have a cartridge, you can insert that to block any unwanted midi signals.

From there, it's just a matter of sending the right midi messages to get more out of the chip. I can switch through the 128 instruments, but I haven't figured out some of the more complex commands. The chip has a ton of effects built in, including reverb, portamento, chorus, flanger, etc. I haven't figured out how to get my controller to send the messages to activate them, but my controller has a limited interface.

edit: here's a diagram

[noystoise]

wow! that is pretty cool. i used to see those everywhere but now not so much. wish i had picked one up while i had the chance. good find!

[crossedout]

this is really great

[Gordonjcp]

MIDI is actually a current loop interface, and you should have an opto-isolator connected with the LED across pins 4 and 5 of the MIDI socket.  There are scads of diagrams of this sort of thing on the 'net.  Try it, and see if you find you get a more reliable interface - especially if you've got several things hooked up.

It's worth noting that on many cheap MIDI cables, pins 1, 2 and 3 aren't connected at all.

[samspike]

I'm fascinated by this, and would consider buying a Musini just for this purpose.

Do you know what chip it is (I'm wondering if we could hunt down other devices with the same chip and/or find the MIDI specs for this chip)?

And, is this same machine - http://www.amazon.co.uk/Neurosmith-Musini-Preschool-Music-Maker/dp/B0000AC9D3/ref=sr_1_1?ie=UTF8&s=kids&qid=1282677974&sr=1-1

[Bogus Noise]

And, is this same machine - http://www.amazon.co.uk/Neurosmith-Musini-Preschool-Music-Maker/dp/B0000AC9D3/ref=sr_1_1?ie=UTF8&s=kids&qid=1282677974&sr=1-1

Sadly not, I bought one of those ones a few years ago when I was getting started in bending, having seen wicked videos of the Musini in the original post. Turned out to be pretty sparse inside and couldn't get anything good out of it - it's even made it into the 'unbendable' thread in the General section.

I'm going to have another go at some point but not holding out much hope, so it's waaay on the back burner right now. Only seen the good ones going on the American eBay in the £20 - £40 range.

[samspike]

You don't happen to know the model number/name of the "good" Musini?

[Bogus Noise]

I don't... but I just searched 'Musini' on eBay and there's actually a lot more showing internationally than I thought, and cheaper. They're going between £5 and £15 but usually about £10. Only stinger is the £25ish postage! Look for the placement of the four coloured buttons - the one you want has them grouped around the front corner.

[theshame]

Do you know what chip it is (I'm wondering if we could hunt down other devices with the same chip and/or find the MIDI specs for this chip)?

It is called a DREAM synth on a chip (or something like that). There are a few models, but the Musini uses SAM9773.

Datasheet (PDF DOWNLOAD)
Userguide (PDF DOWNLOAD)

I'd love to know if other devices use this chip. I'd also love to see more people doing more with Musinis, they are my favorite thing to bend so far.

[samspike]

Wow that chip's a monster

About 200 sounds, 4 drum kits, velocity, aftertouch, multiple types of reverb, chorus, flanger, panning, filters, **stereo**.

[noiseybeast]

What I just realized.

If you're interrupting the Musini's local midi control with that wire cut, doesn't that mean the Musini can be used a midi controller?

[theshame]

Hmmm, interesting idea. I'm not sure how the ROM data works. My guess is that some part of the circuit steps through the sequence that's programmed into the cartridge. Possibly part of the cartridge itself. I suppose I'll have to just try it out.

[Gordonjcp]

Well, the datasheet tells you where the MIDI signal goes into the sound chip, so I guess you could trace it back across the board.

Got any decent pics of the inside of it?

[Bogus Noise]

And, is this same machine - http://www.amazon.co.uk/Neurosmith-Musini-Preschool-Music-Maker/dp/B0000AC9D3/ref=sr_1_1?ie=UTF8&s=kids&qid=1282677974&sr=1-1

Sadly not, I bought one of those ones a few years ago when I was getting started in bending, having seen wicked videos of the Musini in the original post. Turned out to be pretty sparse inside and couldn't get anything good out of it - it's even made it into the 'unbendable' thread in the General section.

I'm going to have another go at some point but not holding out much hope, so it's waaay on the back burner right now. Only seen the good ones going on the American eBay in the £20 - £40 range.

Ok... just for fun I had another quick poke around... you can pitch them with an LTC1799, but they're still boring... definitely don't bother

[talkingfox]

Improved MIDI diagram: (edit: ignore the GROUND label above the yellow wire)

(Optoisolator circuit "borrowed" from the fine folks at http://www.notesandvolts.com)

The original circuit might "work", but it might end up killing your Musini over time for two reasons:

• The original design would result in 5 or more volts going in an input expecting a maximum of around 4.5V. The datasheet specifies an absolute maximum of VCC+0.5V. The Musini's VCC appears to be 4.5V.
• The MIDI standard calls for an optoisolator. The Musini doesn't have one.

If your Musini shuts off more often than you want, replace the trigger circuit (the white box) with a cheapo 555 Timer Module:

If you wish to use your Musini as a MIDI synth, perform both mods and insert a cartridge.