Hi-Hats Concept

The hi-hats sounds are based on 'true' white noise coming from a transistor based noise source - a little tip about transistor based noise source: use PNP transistors as a noise source (i use standard 2N3906 types) instead of the normally used NPN transistors, i compared the noise level of some 2N3904 (NPN) and 2N3906's and found out that the noise level fluctuates a lot for the 2N3904 but for the 2N3906 the average noise level is much higher and it fluctuates less - the noise is then fed through a decay-only controlled VCA. The envelope has two decay times, one for the 'closed' case and one for the 'open' one. For each triggering the envelope is restarted. The noise is then filtered with a 12dB high-pass filter. Thats it!

Snare Drum Concept

Lately i was working heavily on the sequencer software, fortunately a basic version of it now works! for me debugging is a painfully boring yet demading task which is don't like at all. Especially because digital circuits are not likely (at least this one was not) to show any funnly behaviour when working incorrectly. Debugging analog sound circuits can be very inspiring and funny since in general malfunctioning circuits tend to make some sound which is of course is not what you expect, sometimes even better than that.
Lets come to the snare dum concept. The sound source is six oddly detuned square wave oscillators which should make a 'grainy' noise sound. This sound is then fed through a normal decay only evelope controlled VCA. An additional 6dB high pass filter is added to be able to shape the sound a little bit.

Writing Software and Burning Atmega8

Currently i've finished the controller hardware part and the software. At the moment i'm trying to test the software. Problem is that i've managed to burn four Atmega8 microcontrollers while trying to program them. For those of you not familiar with Atmel's microcontroller see Wikipedia or AVR freaks. Unfortunately things get expensive quickly once you burned some of them. So i spent hours testing the boards where the atmega's were mounted but couldn't find any errors. Since i've done all my programming with a cheap home-built programmer in the end i suspected the programmer to damage the atmega's. So i forced myself to spend 80 euros for a 'real' programmer (the avr dragon) with this i hope to prevent damaging more micros and even bringing to life the 'dead' ones. The software will be published (und GPL) once working.

Some photos of the case

The case in the beginning (unmodified). The plastic separators have to be taken out.
Some plastic separators melted out... was a long and tedious work
LED and rotary switches mounted, staring the wiring of the user interface components
The switches are wired the leds not (yet)
front view (note that the paper layout gets glued over the switches again once finished), probably the layout for the 'upper' part isnt finished yet.

Bass Drum Module Demo Video

Hello everyone

My first video demonstrating the bass drum module of my drumsynth is finished, have fun ;-)

Bass Drum Module - Concept and Layout

Lately i started working on the sound-modules themselves rather than the 'computer'-part controlling the entire thing. I started with the bass drum module because it is one of the most inportant modules. When working with software drum synth or synthesizers in general i always found it difficult to create a bass-drum sound which is punchy and pumping at the same time. Another important aspect for this project is that the electronic should be as simple as possible and the electronics should be buildable with cheap and easy to find parts.

The core of bass drum modules is a 40106 hex inverted-based oscillator. Normally this oscillator is used to create rectangle-wave signals. However one can also get something like a triangle-wave signal when using the voltage at the input rather than the output of the hex inverter. The frequency of this oscillator is controlled with a decay envelope and a pot.
The output the goes into a voltage controller amplifier. The volumes is controlled with a simple envelope which consists of a decay envelope signal and a square pulse signal summed up. The idea is to have a punchy attack, done with the decay-envelope and some kind of a compression effect, done with the square pulse.
The schematic of this layout is shown below. At the moment the module is built and being tested, sound clips and/or vids following soon, stay tuned!!