I wanted to build an original, hands on percussion creation environment where I could create drum sounds different from anything I had heard before. The machine can be run from mains but for safety I will carry out all the work using the 9 volt battery power. I wanted to build something robust, versatile and practical as well as interesting.
These are fantastic project machines as they are very much the lowliest of the roland drum machines, but are still roland machines nonetheless. Unmodified they offer that great 80's mono drum sound, but very little versatility with regards to the variety of sounds you have to interact with and how you interact with them, as well as having a typically unintuitive 80's interface. I felt that it was important not to lose this originality, so I made the decision to build modular mod boxes, enabling the machine to stand alone when neither of the modules are connected. These additional modules provide an excellent method of manipulating the beats, while avoiding the clunky, awkward and ineffective 505 interface. It also kept the appearance of the machine standard and removed much of the risk of ruining the casing. I used two DB25 connecters/cables mounted on the casing to make the connections to the external modules.
There were a wide variety of bends I discovered in the machine that I wanted to work into it, but in the end it came down to which were the most influential on the sound, and which were the most cost effective, and a few compromises. I also continued to think about the stand alone nature of what I aimed to do throughout. I experimented with glitching different chips such as the sequencer, but this ended up giving the machine a sort of brain damage which required a full hard reset, so it wasn't practical. I was also going to fit a pause switch, but after experimenting with it, I couldn't find any way for this to be musically applicable, so I chose not to fit it.
This was a difficult project, as it required a lot of wiring at a level above my ability, but I feel my knowledge of working with electronic musical circuits and even 9 volt circuits in general has advanced a great deal. I feel the machine I've created has achieved just what I wanted, it allows me to interact with the circuit, creating interesting and abstract environments, and original, individual sounds which are very difficult to replicate. It puts you right in the moment where you catch just the right sound. Before it was a good machine, its a great machine now.
This was the drum machine in stock standard condition, fully assembled, before any of the work started.
Below is the top side of the circuit board initially visible when you lift the top of the machine off. This is useful to reference the components over which bends can be found.
This is the side of the circuit board where the majority of the project work will take place. It is by contacting this circuit board that I will find all of the bends.
IC3 Chip Glitch
A closer shot of the IC3 chip. This is going to form the core bend of which I will be working on. The idea was to solder up to 25 of these pins to a contact point on an external module, but one issue I faced that is difficult to demonstrate with this picture, is exactly how small and close together these connections are, so I had to settle for only 11 connections. This still leaves us while a wide variety of attainable sound combinations.
Below is the DB25 connecter used to connect the chip pins to contact points on the external module. This was the original ideal number of connections, with all 25 connections on the DB25 connector filled.
Below: The ribbon cable wired to the underside of the IC3 chip.
Below: This is the connecter mounted on the case of the 505
Above: The DB25 cable connected the first module
Below: This is the IC3 glitch control panel. Basically, each of these screws represents an IC3 pin. Any number of these screws can connect to each other in any order, and different combinations of effects can be achieved.
Below is the wiring of the first module.
Pitch Bend
Also wired through the first connecter and into the first module, is the simple pitch bend. This simply involves a body contact point over the R39 resistor of the circuit. This is an interesting feature and ties in directly to my hands on design, as it allows the user to directly interact with the circuit board. This is perfectly safe as the machine only carries 9 volts, either using 9 volt batteries or a 9 volt wall adapter.
Above is the R39 connection over which the connection will be wired
Below is the wired connection.
Individual Channel Controls
This is the only component of the 2nd module. It involves using 8 switches, with an On-Off-On function, to offer the user the ability to set each channel to mute(on), normal level (off), and overdrive (on). This offers the user interesting dynamic control over every channel of the drum machine. Below is the location of the 8 channels of the machine on the circuit board.
Above are all 24 connections of the channels wired through the connector.
Above are the two connecters mounted to the 505 case.
The finished second module.
2nd module wiring.
.... And the finished instrument, all fully wired and working!
Some footage of the machine being performed in fully modded form.
By Scott Walker
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