Waldorf Streichfett DIY Stand

After making the stands for the Volcas I thought I'd make one for the Waldorf Streichfett - an amazing string synth.  As it only needs to hold one Streichfett, the case design is much simpler to build (with less chance of me messing it up!).

You'll need;

6.5mm Birch Plywood (250mm x 500mm) €2.60 from Modulor Berlin excl. delivery

9mm Birch Plywood (250mm x 500mm) €3.30 from Modulor Berlin excl. delivery

Black 3,9x30mm screws (€5-ish for 800 from Toom)

The 6.5mm plywood is used for the side and the 9mm is used to hold the Streichfett (I use 9mm here because any thinner and it'll split the wood when screwed).

You'll also need;

saw/table saw /sander / ruler / pen/pencil / sheet of paper / drill /tape

Start by choosing the desired angle of your stand...  I laid the Streichfett on its side on some paper until I found a good angle.  I then drew round this, adding a few mm each side for some leeway.  My final dimensions were like this;

I used the 90 degree angle of the A4 paper as the reference angle, then the preferred angle that the Streichfett was sitting on the paper.

To cut the 9mm wood that the Streichfett will stand on I used;

18.5cm width (same width of Streichfett) x 12cm long (so there's no chance of it tipping forwards or backwards as you operate it).  Cutting this part out should be much trouble, just remember to keep it as straight as possible ;-)

With the paper template drawn, you can now draw into the wood

Then mark out the other part (just reverse the paper)

First I roughly chopped the plank in two, to make it easier to handle. 

To cut at the correct angles I continued the lines and measured the angles and set the table saw to the same.  If you're using a normal saw you could also use this as a guide line.

With both the parts cut out, I compared them and then sanded them down until the matched perfectly.

I then sanded the main panels for smoothness and the edges at 45 degrees.

Now place the Streichfett where you like it to sit (making sure it doesn't overhang or anything).  Mark a line at the bottom of the Streichfett, then place the 9mm board and mark the edges here.

Use a ruler and calculate the exact centre, then mark two spots diagonally where you'd like the screws to go.  You only have to do this to one panel.

Tape the two panels securely together (you don't want them moving) and for a better finish you can mask with tape where the drill enters and exits (not pictured, but this will help prevent splintering).

Now drill these holes.

Once drilled, measure the distance of the spaces...

...Then mark these spaces on both sides of the 9mm board.

Then drill guide holes into the centre of these markings on both sides of the 9mm board.

Add the screws to the board but only drill them through enough so the tip is barely coming out the other end.

Match the screws up to the guide holes, and then start to slowly screw them into place, making a few turns before changing to the other screw (this will help prevent any warping of the angle).  

Repeat for the other side.

You should now have a pretty cool stand for your Streichfett!  You could varnish it from here, but personally I like the exposed wood look.

 If the Streichfett is too loose, you can sand down one side of the 9mm board, just make sure you keep it straight.  Another way around this is to use double sided velcro.

 Enjoy your new stand!

***UPDATE Arduino Drum Machine****

Simplified Schematic

Ok, so this 'simplified' schematic might not actually make things any simpler!  But some people have asked for it, so maybe it'll help clear somethings up a little bit - especially how to wire up the audio output and pots/switches.  This was drawn from memory so I hope it's correct - give me a shout if not and I'll update (the pots might work in reverse, but they'll still work).  I'd also urge you to look at the schematic on Jan Ostman's website for more help;

https://janostman.wordpress.com/the-o2-source-code/

Thanks!

***Update to the Update***

If the linked website is no longer working, use the Internet Archive to visit a cached version of the site (copy and paste the address and choose a date from around when this pages was posted: around Dec 2016).

***MIDI update***

From the forums of Look Mum No Computer, somebody has posted the code but with the MIDI update;

https://www.mediafire.com/file/5hwyuvykzn8kszg/O2minipops2midiout.ino/file

(Read the forum for more info and schematic).

Older Stuff: A Handful of Different Modules

Over the last few years I’ve made quite a few different modules, some never get to leave the drawer due to space, and others get slowly changed as my needs suit.

Pictured above is a 6-into-1 mixer (for the volcas), a delay, a fuzz, and then an MFOS synth.

The delay came a Velleman kit from Conrad, which is always fun, but since then I’ve built a few others using the classic PT2399 IC.  

The six into 1 is I cobbled together from various schematics from the book ‘Handmade Electronic Music’ by Nicolas Collins.  

This book is great for just getting out and making things, with lots of simple but effective ideas that you can easily build upon. Highly recommended.

****UPDATE**** SIMPLIFIED SCHEMATICS FOR MAKING THE STRING SYNTH

Below is a simplified schematic for the string synth...  Sorry it's not the best quality I'll try and take a better picture later, but hopefully this should be of help those of you new to schematics that want to try and build this synth. 

The connections where it says 'goes to keyboard', you can see elsewhere in this blog for another detailed diagram of where and how these can be wired up to the keys.   As for the potentiometers, I *think* I've drawn them the correct way (if you make this and the pots are working the opposite as you'd expect, swap around the ground and 5v connections on each pot).  If the drawing is incorrect, let me know and I'll re-do it. Even if this version is wrong, nothing will break & it'll still work OK (just the pots will work in reverse). 

You can see where the pots 5volt and ground connections need to go in the diagram, I didn't join them in the picture because the wires would start overlapping and become confusing.  It's pretty obvious what to do though.

Also drawn is the audio out headphone socket, with the positive voltage/audio signal coming from the output D11, which then goes through the resister/capacitor (which acts as a filter to reduce some of the noise from the Arduino).  The other side of the audio goes to the ground signal.  If you don't know how to wire up a audio jack, maybe google 'audio jack pin-out' or 'audio socket wiring diagram'.

If you plan on adding the analogue filter, you'd leave off the audio jack and have the previously mention positive wire go into the input of the filter.  You'll have to learn to read the schematic for that I'm afraid, as I couldn't really simplify it without it becoming more complicated than a normal schematic.  Give me a shout if you get stuck though.

Good luck! 

P.S

I'll draw a simplified schematic for the Arduino drum machine soon.

****UPDATE PART 2******

Below is a wiring diagram to add a bypass switch to the filter;

...And if you were struggling to figure out how to wire up the Pots for the filter, I've drawn out a simple picture showing how (I've had to do this whilst away traveling, so it's partly drawn from memory but I'm pretty certain it's correct)...

Obviously the drawing only shows how the pots are wired and not the full schematic.  Go look at the proper schematic for the rest of the plans, but this will give you a good idea of how to wire up the pots.

Powering the filter from a 9v Battery will give it it a bit more 'oomph', so if you'd like to do that, the below illustration will give you an idea.  Further, should you want an LED indicator showing if the filter is switched on or not, see the chequered box;

I only had SPDT switches available when I built the synth, so that's why there's separate switches for both the on/off & bypass, but you could easily just use one 2PDT to save space.  You could even add an audio in jack at the start of the filter to process other audio.

Good luck!

From Goddard to Apollo EdX Short Course

By far the easiest course I've so far completed on EdX is From Goddard to Apollo: The History of Rockets Part 1.  That's not to say it wasn't enjoyable or that I haven't taken anything away from it, but comparing it to another introductory course like CS50 is like comparing apples to oranges.  I guess that's not really the courses fault though and it was pretty interesting learning about the origins of rockets, it's just that it never felt to me as though it was really pushing you. You do have to write some assignments, so it's not all just watching videos, but I'm not even sure the assignments get checked by another person.  Once you've submitted the text, you're asked if you've completed all the required points; I'm not sure if I could've just submitted a picture of a cat and it would've accepted it or not, but some sort of feedback might have been good.  Still, if it helps stop the brain from rotting any further then thats good.

Weller S32 solder tip replacement - fake?

My S32 tip for the Weller WHS40 soldering station fell apart pretty quickly, so when it's replacement turned up it seemed strange that it was a different size; Maybe the one I'd been using was a fake?  Or the new one is a fake?  I guess only time will tell if this tip will dies like the old one.  Reading into the amazon reviews, these chisel tips do seem to have a reputation of falling apart pretty quickly, which leaves me in the strange situation of hoping the new one is a fake that is better made than the Weller version...

DIY Arduino String Synth

DIY Arduino String Synth With Analogue Filter

***Updates at bottom of page - Easy to read Schematics etc****

Just like the Arduino Drum Machine, this is another build based on the amazing work of Jan Ostman, who is generous enough to share the code over on his website;

***Old website***

https://janostman.wordpress.com/how-to-build-your-very-own-string-synth/

***New Website***

http://synthworks.eu/arduino-string-synthesizer/

The suggested $3 dollar donation is quite simply amazing value for money, so if you use this, don't forget to tip!

On top of Jan's work, I've added a 12db filter with resonance (based on this design) to add a bit more sound sculpting to the synth.  Filters are a massive part of synthesis to me (mainly because I can't play but can quite happily turn knob) and an analogue filter really adds to the warmth 'wobble' of the synth.

The filter has a separate on/off switch and bypass switch.  Looking back it would've been better to build that into one switch, and also to move the output further to the right.  Ahhh the power of hindsight.

I wanted the synth to look very Minimoog-ish or Prophet 5-ish, which I think I achieved, but building the case was by far and away the hardest part of the build (due to my own inexperience/stupidity).

Total build time was spread over 3 months and probably took about 20 hours (most of that time was spent staring at nothing trying to think what to do next).  If I were to make it again I think I could get it down to about ten hours, if luck was on my side.

Here's a quick video of it in action;

Parts

The total cost of parts came to about €60, with most of that going on the MIDITECH midi keyboard. I used a cheap Chinese Arduino Nano clone to keep the cost down (around €2), then a few pots and resistors etc again from China. Also high quality plywood from Modulor for €2.90 (I think it was 6.5cmx250x500). The perspex was also from Modulor. Obviously if you don't already own wood stain and glue etc your cost will be significantly higher. For the panels I used my banggood laser engraver, which I think adds massively to the look of the synth.  If you don't have one of these you could use a label printer.

Electronics

Jan's website documents the build process pretty well, so go check there for schematics etc.  I did manage to draw up the wiring diagram which may save somebody a bit of time when hooking up the keys (find it somewhere below).

I started by taking apart the MIDITECH and unplugging the ribbon cables;

You won't need this part any longer so remove it to save some space;

I soldered the Arduino Nano to some perfboard to make it easier to handle (and to screw down to the chassis later on).

Then using some ribbon cables I began to figure out how to connect the keyboards out's with the Arduino's In's.

Eventually I figured out what went where and soldered it all down and covered the connectors with heat-shrink. You'll probably save a bit of time if you use this;

That's the majority of the synth finished!  From the nano's output I added a bypass switch and then the 12db filter.  I forgot to take any pictures of that though until it was already attached - sorry!  But it all fitted onto another small perf-board;

The Case

I started by cutting some cheap board and securing the key-bed onto it.  This gave me an idea of the final size of the synth to which I based my design around.  I kept the bottom plastic of the MIDITECH (always capitals!) keyboard because it would secure down easier (using it's screw holes) and also because it would probably be a pain to try and re-construct it any other way.  I also added some 'feet' at this point.

Feet...

With bottom panel size known,  I sketched out the rest of the case...

The side panels;

All the parts have been cut here (the other bit of perspex with the dials on was temporary just to make sure it was still working);

Notice the pencil with my name written on it.  That's mine it is.

Then using my old friend Ponal Wood glue I started sticking everything together (including fingers, clothes and everything else);

Then it was time to design the front panel and the laser engrave it onto perspex.  The smell was awful (and toxic)...  I stayed in the room long enough to feel faint.  I did sleep well that night though.

Running a test on card;

Burn!

After it was engraved I filled it in with white acrylic paint;

 With the panels and case completed it was time to stain the wood.  I used a mahogany brown stain, using two or three coats.  The trick here is not to use to0 much and to keep it moving when it's been applied, otherwise you'll get an uneven finish.

 Once this had dried it was time to add the varnish.  Like with the stain, I find it's best to use only a tiny amount and spread it out as much as possible to get the best finish (you can always add another layer later).  With this synth I found one layer to be enough;

Once this has dried you can now put it all together.  For extra security I also used some hot glue to do this (and it's not fallen apart yet)

I added screws to secure the perspex panel but can't find a picture of that. But I'm sure you can imagine what it looks like.

Conclusion

Overall I'm pretty happy with how it turned out, with only a few gaps in the wood caused by my rubbish cutting/maths skills.  Should I make it again I'd move the output over to the far-right as I've noticed it's possible to knock the cable when going mad on the filter (you should only touch a synthesisers knobs as if they are really hot, otherwise you're not a real synthesist).

I've been learning C for a while, but it's a massive mountain to climb.  From here though I've bought the following book;

When I eventually get around to reading it, it should give me a better idea of what's going on in the code, then I'd like to attempt a version 2 using maybe an Arduino Due and add some more controls.

Thanks!

****UPDATE****
SIMPLIFIED SCHEMATICS

Below is a simplified schematic for the string synth...  Sorry it's not the best quality I'll try and take a better picture later, but hopefully this should be of help those of you new to schematics that want to try and build this synth.

The connections where it says 'goes to keyboard', you can see elsewhere in this blog for another detailed diagram of where and how these can be wired up to the keys.   As for the potentiometers, I *think* I've drawn them the correct way (if you make this and the pots are working the opposite as you'd expect, swap around the ground and 5v connections on each pot).  If the drawing is incorrect, let me know and I'll re-do it. Even if this version is wrong, nothing will break & it'll still work OK (just the pots will work in reverse).

You can see where the pots 5volt and ground connections need to go in the diagram, I didn't join them in the picture because the wires would start overlapping and become confusing.  It's pretty obvious what to do though.

Also drawn is the audio out headphone socket, with the positive voltage/audio signal coming from the output D11, which then goes through the resister/capacitor (which acts as a filter to reduce some of the noise from the Arduino).  The other side of the audio goes to the ground signal.  If you don't know how to wire up a audio jack, maybe google 'audio jack pin-out' or 'audio socket wiring diagram'.

If you plan on adding the analogue filter, you'd leave off the audio jack and have the previously mention positive wire go into the input of the filter.  You'll have to learn to read the schematic for that I'm afraid, as I couldn't really simplify it without it becoming more complicated than a normal schematic.  Give me a shout if you get stuck though.

Good luck!

P.S

I'll draw a simplified schematic for the Arduino drum machine soon.

****UPDATE PART 2******

Below is a wiring diagram to add a bypass switch to the filter;

...And if you were struggling to figure out how to wire up the Pots for the filter, I've drawn out a simple picture showing how (I've had to do this whilst away traveling, so it's partly drawn from memory but I'm pretty certain it's correct)...

Obviously the drawing only shows how the pots are wired and not the full schematic.  Go look at the proper schematic for the rest of the plans, but this will give you a good idea of how to wire up the pots.

Powering the filter from a 9v Battery will give it it a bit more 'oomph', so if you'd like to do that, the below illustration will give you an idea.  Further, should you want an LED indicator showing if the filter is switched on or not, see the chequered box;

I only had SPDT switches available when I built the synth, so that's why there's separate switches for both the on/off & bypass, but you could easily just use one 2PDT to save space.  You could even add an audio in jack at the start of the filter to process other audio.

Good luck!

***UPDATE Arduino Drum Machine****

Simplified Schematic

Ok, so this 'simplified' schematic might not actually make things any simpler!  But some people have asked for it, so maybe it'll help clear somethings up a little bit - especially how to wire up the audio output and pots/switches.  This was drawn from memory so I hope it's correct - give me a shout if not and I'll update (the pots might work in reverse, but they'll still work).  I'd also urge you to look at the schematic on Jan Ostman's website for more help;

https://janostman.wordpress.com/the-o2-source-code/


Thanks!