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I post articles with text, photos and videos about the amazing AMSynths analog synthesizer modules.
You can buy them at www.amsynths.co.uk

Friday, 23 September 2011

AM8071 Snow Fall VCF

IntroductionBack in the late Winter of 2009/2010 there were heavy snow falls in south east England for the first time in many years. During this "white out" I designed a diode ladder voltage controlled filter similar to the ones that appeared in a number of analog synths in the 1970's, and named this new module "Snow Fall". In 2009 I had already built a number of prototype 4-pole diode filters from the EMS VCS3, Roland SH-3 and the Practical Electronics Minisonic 2. I improved the designs with modern components and added a fifth pole and slew delay on the CV input. This AM8071 protptype was very sucessful and delivered a great sounding and flexible VCF.

During Summer of 2011 the prototype was worked up into a production design using the new AMSynths panel design which has a mix of rotary and slide pots, with momentary push buttons. The production units were launched on 20 September 2011 and this EuorRack module is available to purchase from AMSynths web site.

AM8071 Module
The filter is a Diode Ladder Low Pass with a cutoff rate equivalent to 18dB per octave in 4-pole mode, and 24dB in 5-pole mode, thanks to the characteristics of diodes. The filter has a large Frequency rotary control with smaller rotary controls for adjusting Resonance and Resonance CV (QCV) which enables voltage control of Q. The filter has a maximum Q of 20 and will self oscillate at higher settings. There are 30mm slide potentiometers for adjusting two signal input levels and two frequency CV amounts. There are five input jacks and one output.
The module uses momentary push buttons to control slew and slope rather than clumsy toggle switches. The enables analog switches placed close to the filter to activate these functions (keeping the analog signal path short) and for green LED's to show the status - on or off.

AMSynths PanelThe panel is professionally manufactured in 1.6mm thick alumnium in Germany with black lettering. The module is EuroRack sized and fully compatible with many other EuroRack modular synthesizer systems such as Doepfer.

More Information

Visit the AM8071 web page on my web site for more information.


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