Tuesday, 15 November 2016

Korg Mini-Pops DIY Drum Machine

Korg Mini-Pops DIY Drum Machine 




This is a really cool build;  It a recreation of the Korg Mini-Pops drum machine, an instrument which has been on a ton of records the most famous of which might be Jean Michelle Jarre’s ‘Oxegen’ album, hence this clone being called the ’O2’.  



The brilliant Jan Ostman built this using only an Arduino nano and a few barebone parts.  Jan is giving away the full details on his website and is only asking for a $3 donation in return.  Bargain!


***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;
(Read the forum for more info and schematic).

***More Advanced Model Update***
If you'd like to build a more advanced version, head over to the NoiseyMaker website for more info and a nice detailed guide.  This version builds on the original & adds some advanced features like a display and even pitch control of the samples.  Also the drum patterns have been updated to be a bit more 4/4 time 'electronic-style', rather than than some of the 3/4 time waltz in the original code (you could always copy & paste these over to the old code if you wished).

....



I started by building my first version using a cheap Maplin plastic enclosure, but I thought it was worth spending a little more time on it so I got the table saw out. 














Because the table saw has a maximum cutting width of 7cm, I based the case around this limitation.











The switches mute the individual drum hits. The pots select the pattern and its tempo.





































V3.




***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!

Tuesday, 1 November 2016

DIY Jesus & Mary Chain Fuzz Pedal

DIY Jesus & The Mary Chain Fuzz Pedal


This was my attempt at the Jesus and Mary Chain Shin Ei Fuzz Wah.  The Mary Chain pedal was famously faulty which I wanted to incorporate the same nastiness into my version.  Also the original pedal was a wah-pedal, but I don't have the means to build that.  So I thought about it; a wah-pedal is essentially just a filter, so why don't I just add a filter onto the original schematic, so that you can drive it into self oscillation creating the feedback that it was known for?


After building a few different schematics I'd found on the web, I went with this one as it sounded the best to my ears;


However, note that this isn't the actual fuzz pedal schematic, but just the fuzz part of it.  That's ok, because this is where I add the following filter tat's capable of self-oscillation;


I've put this filter into loads of different build before because it's simple but sounds pretty good (or nasty if that's what you want).

I then added numerous bypasses, and the ability to run the filter and fuzz separately.



For some reason after building this I put it away in the drawer and forgot about it, which is a shame because it sounded pretty much like the mary-chain in a pedal.  I should probably get a batch of PCB's made if I build any more because it was a lot of work making it on perf-board.  

One day I'll do that and post some audio-examples.

Tuesday, 25 October 2016

Korg Volca DIY Stand Guide

Korg Volca DIY Stand


I’d seen lots of nice looking, but very expensive cases for the Korg Volca series, so to save some money I thought I’d try to build my own, with the very real possibilty of losing a few fingers :-)  

It actually all turned out pretty ok with no digits lost, however the problem I did have was with the case of the volca stand; this was either my poor woodworking skills or perhaps not having the correct equipment.

Where the case has a fold in it I managed to nick the other side, so it isn't quite as neat as it should, but it’ll do for now.  It's maybe a job for a dremel to do properly.  

I found that I had to use a thicker piece of wood for where the Volca sits, as otherwise because of the size of the screws, the wood will split (you could of course use smaller screws here but I didn’t have any).



To build the stand I used;

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)


You'll also need;

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


I started by drawing out the angles of the stands, there were a couple of different angles I could have used, but I finally settled on 30 & 60 degrees.  One thing to note here is that you can turn the stand upside down and use the reverse angle, which gives a sharper incline.





…Then I drew around the sides of the actual instruments, with them being at the correct angles and figured out the correct dimensions from here (remember to give yourself some lee-way here, hence the 11.5cm volcas shown below are each given 11.7mm).  This give you a nicer edge without risk of the Volca overhanging.


Now draw this out on paper...  using the edge of the paper as an exact 90 degree angle (as I'm sure this'll be straighter than anything I could ever cut.


With the paper cut out (use only one piece of paper and simply reverse it for the other-side, you'll save time and get the exact duplicate), now mark out the outline on the wood.































Lovely! Now mark the other one out. 

TIP: Make sure you use the 90 degree angle of the wood, unless you have some quality cutting equipment (again, the people cutting this have better equipment than me, so I'm relying on them to cut straight.  Not the best method really, but what can you do)






With both sides marked, it's now time to cut them out.  To make this slightly easier while using a tablesaw, I'll cut the board into more manageable pieces (you might not need to do this if you're using a saw).











Cutting the wood into more manageable sized pieces...














Then cut out the main bits














At the intersection of the two Volcas, it's almost impossible to cut accurately...











...But with a little patience you can achieve an acceptable result















Cutting the 9mm wood: Use this picture to help cut the board. The length should be the same with as the Volca and the width can be shorter than a volca, as long
as it can sit on the wood without tipping over.


I used: 19.4cm x 9.8cm











The edges will be rough after cutting so we'll sand them down











I used a sander but sand paper will also work.










To smarten up the badly cut intersection, I used these files that you can get in Maplin.


























Once all this was complete the boards came out looking pretty good:


























































Here's a little gif of the preceding steps;















Now we need to think where to sit the board that will hold up the Volcas.  To do this I marked out a line underneath the Volcas while positioned correctly on the board.














Remember the board needs to be 9mm otherwise it'll split , unless maybe you're using smaller screws than me then you might get away with it.  












Roughly draw out the 9mm board outline using a ruler - making sure it won't overhang or anything.

You only need to mark out one board for this.

Use a ruler to find two centre spots for the
two screw slots (look at the picture if that doesn't make sense!).  Remember the distances for later.









Now secure the two sides together using tape.  Make sure they're tight and don't move.











 Also mask where the drill holes will be.  This'll help prevent the wood from splintering.
















With them secured, drill through both pieces at once.


















Photo of all four drill holes successfully drilled.






 



Hopefully you've remembered the distances of the holes, because you need to now mark the same on the two pieces of 9mm wood



















Now carefully drill the exact centres of the wood.  This will create a guiding line for the screw.















Now put the screw in the sides, but don't go through all the way yet;
















With the screws just barely poking through the sides line up the 9mm wood
















Then slowly turn the screws

Tip:  only give a few turns on each side of the screw before changing to the other screw so they go through evenly and at the same time.




 





 Go slowly so you stay precise and don't split the board


















It should be looking almost finished by now, we just need to do the same with the other side.








Now just add the volcas!  You may have to loosen one side to get the volcas in, if this is the case then at least they'll be snug and won't fall out (be careful you don't over tighten it and squash the machines!).  

If you've left too much room you have two options; you can either sand down the side of one end of the 9mm board until the fit, or secure them in place with some double sided velco.



I personally think these stands looks pretty snazzy as is, but you could easily varnish them now if you so wish.

I hope this guide helps somebody!