The Beginning

Today I'm starting the blog which is dedicated to the development of an analog drum synthesizer. I was asking myself for a long time if I really should start this since there are already too many blogs out-there (in my opinion) with doubtful content sometimes. Anyway, this is about building a analog drum computer. A drum computer is a device on which rhythms can be programmed, it is one of the basic ingredients for all sorts of electronic music. There are some famous examples of drum computers such as the tr-808 from roland which is unfortunately not produced anymore. My own design will be heavily influenced by the tr-808 although i never had an example in my hands. I'm mainly doing this because the tr-808 is considered to be a classic and it looks cool too. And i've player around with the virtual version of it (Propellerheads rebirth). So whats my motivation for building a drum computer? If you just want to create beats then you probably use a pc and a software drum machine. There are some good ones out there for free (for instance propellereads rebirth. Thats not a i want to do with is. I'm rooted in 'live played' music and i'm a guitar and piano player for a long time so i don't really get along well with creating music by clicking on virtual buttons on a computer screen. I'm happier with a hardware instrument which is quickly started and easy to use (one button - one function, no menus). Well in this case a hardware groovebox could do the job so why still build a drum computer myself?
First: building an instrument is fun, and, once finished, a deeply satisfying experience.
Second: There are almost no drum computer diy projects on the web. With this project i hope some give something back to the synth diy community of which i benefitted a lot during my first synth diy projects. I will post some information on these later on.
Third: A self-built instrument is very easy to use is the since you built it the way you want to have it.

Basic Concept

Before starting the first sketch of a schematic i put up a list of general features the drum synth should have. The basic concept is a step sequencer based drum computer with analog sound generator circuitry. The pattern control and programming is done with atmega8 microcontrollers. These are chosen because they are relatively cheap and they can be programmed with very little extra hardware required. The following sound modules will be built:
->Bass Drum
->Snare Drum
->Open and Closed Hi-Hat
->Tom
->Crash
The sequencer should have 16 steps, it should support 4 running modes:
->forward (the standard one)
->backward
-> forward followed by backward
-> random
Beside a clock is supports also a manual advance mode. A 'swing'-mode which enlarges every second note period is not planned currently. The sequencer will be able to control eight instruments whereof six are integrated in the drum synth. The sequencer will have a trigger output to control external equipment. One instrument control line is reserved for a digital sample player which might be added later on. Each trigger pulse will have a normal and an accentuated mode, the amount of accent will be tunable for each sound module separately.

There will be the possibility to store 4 patterns in the internal eeprom of the atmega8's. It won't feature a 'song-mode', i.e. the ability to store a sequence of patterns since it is designed as simple instrument which will be played as 'life' as possible. But we'll see, maybe i add that later on. However it supports playing one pattern while programming another one, as many things else this is shamelessly copied from the tr-808. Thats it so far. Next i will some sound clips of the prototypes of the snare and bass drum modules since i already built as well as some information on my finished synth projects, schematics etc. Beside electronics i play music solo and in a band.