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Midi English 48key Coming Up !


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Hello everybody,

 

Having converted many acoustic accordions and old electronic accordions to MIDI over the last few years as part of my business, I've finally decided to bite the bullet and convert a salvaged Lachenal that I bought from Chris Algar a year or so ago. It was always my intention to get around to it but you know how it is.

 

I've got some spare time having finished the Jeffries G/d, shown elsewhere on this site.

 

My intention is to do the MIDI conversion during the next week or so and post pictures etc as and when progress is made.

 

The system I will be using is that which I developed for accordion over 3 years ago, the hardware and software designs are my own and will be adapted for the concertina.

 

First some pictures from today:

 

post-623-1112982260_thumb.jpgpost-623-1112982291_thumb.jpg

post-623-1112982347_thumb.jpgpost-623-1112982380_thumb.jpg

post-623-1112982408_thumb.jpgpost-623-1112982438_thumb.jpg

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I've already decided how to go about it with this prototype.

The system will be non contact using magnets and Hall effect switches.

The concertina will be reed free.

Bellows pressure will be measured and used to control MIDI expression.

For the moment it will be single MIDI channel, 0.

Voice selection from the expander only.

Cable connection.

Bellows calibration switch (momentary) and bellows effect potentiometer will

be provided.

 

I've started so I'll finish, let me know your thoughts.

 

REGARDS

 

Roy Whiteley

Accordion Magic Ltd

www.accordionmagic.com

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Sure,

 

The old fashioned way of attaching switches to a musical instrument i.e. accordions, was to fit spring-wire switches or very fragile 'springy coils' to the mechanism. I had indeed considered this in this application.

Having stared at the limited space for a while I finally decided on the more modern method of determining when a key is pressed using magnets and Hall effect switches.

 

Three semiconductor Hall effect switches and two different size magnets are shown in the fourth picture above. The output of these switches simply changes state when the magnet is brought near, nothing touches and nothing wears out AND they are immune to dirt, dust etc.

 

The magnets are attached to the moving part, the lever arm in this case and the switch must be solidly mounted to a PCB as shown in the last photograph. I've made 6 pillars to hold the PCB's in place... close fit.

 

I'll try to fit them all to the right hand side today.

 

CHEERS

 

Roy

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Right side complete!

 

post-623-1113056148_thumb.jpgpost-623-1113056170_thumb.jpg

 

As you can see, all switches and magnets fitted to right hand side. Connections to each switch have been made through the action board with purple insulated wire.

The 0 volt and scan lines will also pass through the board and connect directly to the hexagonal 'bus'. The 24 switches will be scanned in two groups of 12 because my existing circuit and software has been optimised for a 12 bit accordion system and there is absolutely no need to change it to an 8 bit bus for example.

 

Thoughts; When this is finished, it would be relatively simple to add a switch and convert it to anglo............ If you rotated the instrument through 90 degrees and had Anglo straps also fitted, could you play it as a 48 button Anglo?. I can do it if you can play it.

 

I can imagine a future instrument with slightly curved rows that would be easier to play as an Anglo but still playable as English... somewhere in between. Not even thought about Duets?

 

I am intending to fit restrictors behind the board so that it feel like a reed instrument, these I imagine will be cardboard circles with a single hole stamped in it to allow some air to pass. Perhaps one button should be left open and used as an Anglo air button?

 

CHEERS

 

Roy

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It would be very interesting to know how this design compares with the midi instrument that is about to appear in production at the Concertina Connection and which has been under development for some time.

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It would be very interesting to know how this design compares with the midi instrument that is about to appear in production at the Concertina Connection and which has been under development for some time.

 

Yes it would.

 

Both sides now finished as can be seen below.

I will build the prototype circuit board over the next couple of days and try it first without the bellows pressure. Should be finished including bellows pressure before the end of the week!

 

post-623-1113141718_thumb.jpgpost-623-1113141752_thumb.jpg

 

I'm going to build the circuit onto the inside of the left hand end.

 

CHEERS

 

Roy Whiteley

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That's incredibly tidy. I love those hexagonal power/ground rails.

 

I've always wondered how the pros did pressure sensing. I was converting a Stagi to midi back when I had more free time, and I couldn't get decent precision from the pressure sensor, a dual-ported Motorola sensor whose packaging was kind of a pain to interface with the box.

 

I was thinking instead of using a single-ported sensor, or maybe a pair of them if that would help with noise. But that's for another time. Cool box!

 

Caj

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That's incredibly tidy.  I love those hexagonal power/ground rails. 

 

I've always wondered how the pros did pressure sensing.  I was converting a Stagi to midi back when I had more free time, and I couldn't get decent precision from the pressure sensor, a dual-ported Motorola sensor whose packaging was kind of a pain to interface with the box. 

 

I was thinking instead of using a single-ported sensor, or maybe a pair of them if that would help with noise.  But that's for another time.  Cool box!

 

Caj

 

The experience I've had with accordion bellows and sensing bellows pressure is that noise is not so much an issue as is drift. It is surprising that despite all your effort, the actual pressure developed inside an accordion or concertina bellows is actually quite low! I've used both guage and diffrential transducers in the past and found that gauge types work very well so long as you use a suitable instrumentation amplifier and provide a means of calibration, either at power up or during a session with a reset pushbutton. Using a devoted instrumentation amplifier is expensive and a more reasonable approach is the 3 opamp method while still maintaining reasonable performance. Dual rail amps can be used with resistor dividing to provide a false earth at half power potential, the bellows direction is therefor determined as being one way from 1/2v to 0v and the other from 1/2v to V. Constant current source is not required.

The trick with bellows pressure is to use software to produce a square or exponential result in volume, i.e. twice the squeeze gives for example; four times the volume or more.

 

Untill next time.

 

P.S. I'm now claiming Lachenals first MIDI instrument; ANY comments....please.

 

Regards

Roy Whiteley

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Very impressive, Roy.

 

I have no idea why I read through your entire post because I have no idea what you are talking about. However, I am very impressed. And maybe one day will understand what you have done.

 

Bravo.

 

Helen :)

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The MIDI system is now fully incorporated into the Lachenal. The MIDI and power connection is now via socket on the left hand end as can be seen.

 

post-623-1113312100_thumb.jpg

 

The next step is to fit the bellows pressure sensor and amplifier as shown below.

 

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It will then take a day or two to restrict the old pad openings in the action box so that the instrument feels natural and at the same time to control volume or expression with the transducer.

 

Still expecting to have finished item by end of week.

 

CHEERS

 

Roy

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I'm now claiming Lachenals first MIDI instrument; ANY comments....please.

I'm sure that Louis Lachenal would have been fascinated, indeed he would probably have already brought out a MIDI model himself, were he alive today, and I'm sure that he would have embraced CNC/laser production too.

 

Interestingly, his great grandson Bill La Chenal followed in his footsteps by building a tone generator, played by Dave Stewart on the album "Egg" in 1970, and has become quite a computer wizard since.

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I'm sure that Louis Lachenal would have been fascinated, indeed he would probably have already brought out a MIDI model himself, were he alive today, and I'm sure that he would have embraced CNC/laser production too.

 

Interestingly, his great grandson Bill La Chenal followed in his footsteps by building a tone generator, played by Dave Stewart on the album "Egg" in 1970, and has become quite a computer wizard since.

 

I was almost sure that Louis Lachenal would have turned in his grave..... however, my claim... 'first Lachenal MIDI' is a light hearted one while remaining true at the same time? I think. I've seen other - 'sort of' MIDI concertina's and could'nt understand why it has not been done properly.

Anyway it's nearly here, I've had many emails and hope to have a demonstator within a couple of days.

 

CHEERS

 

Roy

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It's starting to look like there are at least a couple of folks reading this thread who don't know what MIDI means. Here is a very brief explanation.

 

It stands, first of all, for "Musical Instrument Digital Interface."

 

Imagine an electronic instrument of some sort. It has keys or buttons or some other way of controlling it. It also has a sound module that makes the noise. These two parts need to communicate with each other so the sound module can produce what you're playing on the controller.

 

MIDI is a set of standard signals for this communication, so you can mix and match controllers with sound modules and they all speak the same language, even among different manufacturers.

 

What Roy is doing is making a controller out of a concertina, so it puts out a MIDI signal when you play it and can therefore drive a synthesizer or electronic piano or any other MIDI-compatible sound module.

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Trully impressive.

 

Couple of questions.

 

 

I realise this is a prototype but the connector looks a bit bulky, do you have plans to use another type of connector or go wireless?

 

Yes, the connector is a 'what I had to hand' connector (D type). Normally a smaller screw type would be used.

Problem is there's got to be one somewhere.

I expect the finished unit will be tidier but will have quite a few protrusions from the case! Even wireless needs an antenna!

 

CHEERS

 

Roy

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