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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.