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The woodwind VCO board during prototyping. See details below!

September 2nd, 2007.
I have now completed the testing of the new module and I'm happy to report that it works exactly as intended. Naturally, I had to make some changes to make it work but it was really only minor things. 
OK, so now you're itching to know what the module does. Well, the clarinet in the picture above is a hint. 
The new module is a waveshaper that is mainly intended to mimic the behaviour of woodwind instruments. It is inspired by the vintage german wind synth Variophon. You can read all about the theory on the Variophon homepage. 
According to the theory, the proper way to emulate a reed instument is with triangular pulses where you can adjust the up and down slopes. For some reason, the Variophon used rectagular pulses instead. Probably because it was easier to implement in electronics. Because of this, I just had to test it the proper way, with triangular pulses. And in my circuit the pulse widths are even voltage contolled. To be able to emulate the Variophon, I added rectagular pulse too. And as an added bonus I even added a double pulse, where you can voltage control the width of the positive and negative pulses separately. The circuit diagram for the complete circuit is here.
The circuit can be driven from any VCO with squarewave or sawtooth output and basically works like a linear VC-AD envelope shaper. You could actually use it as just that. The pulse width is independent of the oscillator frequency, which is according to the reed instrument theory. This is where this circuit differs from ordinary pulse width modulation. If you set the up slope slower than the VCO frequency, the circuit will perform frequency division. This can be heard in the last sound clip.
A separare page for this module is forthcoming. In the meantime you can listen to the module in the following sound clips. The patch: Minimoog VCO clone > Woodwind waveshaper > Minimoog VCF clone > Minimoog VCA clone + reverb.

Triangle pulse Double pulse Single pulse Double pulse LFO modulation Double pulse+VCF resonance Sweeping up-PW  

August 23rd, 2007.
Good news! I have finally completed the board layout and etched the board for a new module that I designed over a year ago. I will tell you more about it, when I have found out if it will work or not. It's an entirely new design, so you never know if it will work or not. 

August 11th, 2007.
Because of health issues, I have unfortunately not been able to work on the Bergfotron in a long time. I hope to continue some day, but currently I can't say when. I have some interesting things in the works but I have to cut back computer usage, for health reasons. At least I have now updated my e-mail address, which somebody pointed out was outdated. I thought I had already updated it, that's why it was wrong for so long. I'm sorry about that. 

February 18th, 2006.
Finally a new module! I designed this circuit several years ago, but I haven't got around to test it before. It is a voltage controlled bandpass filter, where you can voltage control all parameters (center frequency, Q-factor and resonance amplitude). The filter will only do resonances and not cuts. It is intended to imitate the formants in acoustic instruments, but could be used for other things as well.
Why voltage control? Well, first of all you can sweep the parameters. But it can also be used to introduce note scaling or other subtle effects. You could also interface it to some patch storage system.
So far, I have a prototype module that works the way I want. I'm planning on building a triple module and to provide circuit board layout for that. In the meantime, here is the schematic diagram.

The Bergfotron with Kenton Pro Solo and Morrison Digital Trumpet in front.

January 4th, 2006.
The midi interface on the Bergfotron  didn't quite manage all the continous controller data that a wind controller generates. Therefore I have replaced it. I now use the Pro Solo II from Kenton, which I have integrated into the Bergfotron (see picture).
The Pro Solo copes with the wind controller data but it turned out that it lacks smoothing of aux controller data. This means that there was annoying zipper noise on the breath contol CV (aux 1 output set to CC2). Therefore I added an analog 24 dB/octave low pass filter that cuts at 50 Hz. This removed the zipper noise completely.
It really sounds excellent, playing the Bergfotron from a wind controller. Even a simple one-oscillator VCO>VCF>VCA patch can sound terrific. Just route the breath CV to control the VCA and then some to the filter cutoff. Stay tuned for a sound clip...

13 may 2005.
I have been working on this small stand-alone synthesizer for a long time. It's now fully functional. Only some cosmetic additions are left to do. Lately I have had very little time to work on synth projects though.
It is basically a clone of the Pearl Syncussion SY-1. But I have designed a number of additions that expand the sonic possibilities considerably. More details to come...

The new Bergfotron percussion synthesizer.

1 december 2004.
This time I'm going to show you how I modified my wind controller to improve the ergonomics. The wind controller is my main instrument and I use it to control digital synths and sometimes also the Bergfotron, via the midi interface. Read more in the new wind controller section.

My modified Steiner Midi EVI.

5 november 2004.
It was almost a year since the last update of this site. I suppose you all think that I have lost interest in synths and stopped working on the Bergfotron. Well, I do have periods of high and low tide, when it comes to my hobbies. But the truth is that I have worked quite a lot on a new DIY synth project, that is separate from the Bergfotron. I haven't yet decided in what form that will enter in these pages. 
There have been some work done on the Bergfotron too, though. I decided to remove the built-in speaker system, as I don't use it in the studio and it made the synth too heavy to move. This also means that I have moved the transformers to the main unit. They were originally mounted in the floor unit. The latter now only serves as storage for cables etc. when the synth is packed up for transport. The speaker grilles on the sides now serves as vents, which definitely are needed. I used steel mesh grilles for the vents, which I took from a broken ghetto blaster, that I found in a dumpster.

The transformers are now moved to the main case. Note the protective cover 
over the parts that carry mains voltage.