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School Rhythmer Peg Matrix

Here are some photos showing the construction of the peg matrix from my School Rhythmer drum machine project: Basically, it involves micro-switches, wires and diodes arranged in columns and rows, creating an 8 x 5 matrix The columns carry the trigger signals from the step sequencer - there are only eight steps - while the rows carry the trigger signals to each of the five drum sounds. When a peg is inserted, it closes the associated micro-switch so that the particular drum sound is triggered at that step. The diodes isolate each switch from the matrix. Without these, any trigger signal would dissipate throughout the whole matrix triggering every drum sound that has a peg inserted along its row, regardless of the current step. The rest is 'mechanical'. I used micro-switches as a cost effective solution. An alternative might be 3.5mm jack plugs and sockets, such as the switching type that make/break a circuit when a plug is inserted. A further idea would be to use tact switches w...
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Ganged Switch Wiring

Just an image to show how to wire ganged switches as an alternative to using a potentiometer with an Arduino, or similar. This allows the user to instantly jump to a desired setting/option with precision. Here are some ganged switches (the six blue buttons) to select patterns on a build of jan ostman's O2 Minipops drum machine: The dark grey button to the left selects between banks for a total of 12 patterns. Note: A simpler (but less speedy) option would be to use a rotary switch. As in the build below:
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Audiowerkstatt trigger2midi2trigger cable

 
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Rotary Speaker - isolation cabinet - Part 4

Part 4 Here's the control box... At it's heart are the guts of a Pioneer MA-12 mic mixer with a spring reverb: I kept the electronics and discarded the case. I made some small adaptations - removing the unnecessary features such as the tape/source selection and associated inputs and outputs, and adding wiring to bring the controls off the PCB for mounting in the new casing. The mic that I installed in the rotary-isolation cabinet is one of these... ...a National electret condensor mic. I'd separated the mic from the power unit thing, which takes an  LR44 1.5v button cell battery, in order to install that part in the control box. Luckily, by tracing the PCB of the MA-12 and testing with a multi-meter, I could find a suitable point to tap power for the mic and so do away with the need for batteries. The above, however, forms only one half of the unit - the output side of the things. The other side is the input and speed control for the rotor....
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Rotary Speaker - isolation cabinet - Part 3

Part 3 A lot of my projects end up in the living room so I typically try to make them part of the 'furniture and fittings' and I tend to have a 'Fisher-Price' approach to interior decor - colourful/playful. The wood I'd used for the isolation cabinet were off-cuts, leftovers and recycled bits, which were all fairly rough so I filled the worst of the old screw holes, scrapes and nicks with dowels and filler.  However, I didn't have the energy, time or enthusiasm for marathon sanding to achieve a smooth finish. Instead, I went with a plaster medium paint which I applied with a roller. This filled and covered over the remaining imperfections reasonably well to leave a nice textured surface. I then painted the two parts - blue for the upper section, beige below, followed by a few coats of water based varnish and was pleased with end result. I added some wooden handles to the upper section so that it can be easily lifted off and pu...
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Rotary Speaker MKIII - isolation cabinet - part 2

Part 2 Concrete We live in a small 'council flat' in Tokyo. There are neighbours above, below and to either side. They're decent folk and I don't want to push it by making too much noise. Nonetheless, I'm sure I disturb them from time to time with my music and DIY activities. They probably can't tell the difference between the two... That's one reason to embark on an isolation cabinet. The other is a question of sound balance since I generally do everything at low volume. The problem is I need to have the rotary speaker significantly louder in order to mic it up to get a healthy signal into the mix. Therefore, unless the speaker is in another room (which I don't have), it will just drown everything else out. This got me thinking that perhaps an isolation cabinet could be the answer? There are acoustic challenges with this approach - not least the way an enclosed space (unless expertly designed) affects the sound in an undesirable way. Typically ...
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Rotary Speaker MKIII - isolation cabinet - Part 1

Part 1 First, a little background... If you don't know what a rotary speaker is, Google "Jimmy Smith" or "Leslie speaker". Constructing rotary speakers is an intermittent hobby of mine. In 2011 I built my first from salvaged parts - a motor from a tape deck spinning a coffee filter over an old Fostex speaker, the speed adjusted by a PC fan controller. Here it is: It garnered a favourable response on YouTube, so I embarked on a more elegant approach, still using salvaged parts but with a little more thought and care going into the design. It took a couple of years to get round to making it but here's the result: It hasn't received as many views or comments as the first - not that surprising since I make next to no effort to promote my online presence but I feel it was a step forward... One issue with these things is they have to be mic'ed up to record the effect. So I got to thinking that some kind of isolation could be a solution....
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