Dual Filter page 1

under construction



Mad Science Lab Dual Filter

Operation and Sound Files





Starting at the middle of the top of this picture

There are 2 seperate filters. Each one has 2 audio inputs with a volume knob to adjust the level going into the unit. At the 3 o"clock position you will get a good signal for synthesizer equipment. Higher setting are good for line level stereo equipment. I have allowed for a little bit of gain here so you can overdrive the filter , which distorts in a very musical way.

At the very top are the 2 outputs , one for each filter. In and Out cables are away from controls.

The Dual Filter also has two low frequency oscillators to produce sine, square, and triangle waveforms. Total of 6 waveforms. The speed of the LFOs can be adjusted from .017 Hz to 40 Hz with the LFO Rate knobs on the upper left portion of the unit. A LED visually shows the rate of the LFO. The lowest frequency is about one cycle per minute.

The frequency and resonance can be manually controlled by the larger knobs at the bottom of the unit.

However things get real interesting when you use the LFOs to modulate the filter cutoff and resonance


Dual Filter Sound Files (All files in mp3 format, please feel free to use without permission)

Unfiltered synth sound This is a Prophet 5 synth playing a single note with the filter cutt off set all the way up. This means the sound is not being altered. This shows what the signal originally sounded like.

Filtered Synth sound This is the above synth sound being processed by the filter. The oscillators are modulating the frequency cut off and the resonance of the filter. This creates a sweeping like sound and the use of both oscillators creates a varying pattern of the sweeping.

Filtered synth sound 2 Here the filter cut off is modulated to a greater extent so the the cut off frequency is effectively cutting most of the audio at its lowest position. The effect is that it chops up the audio. A single sine wave is used to modulate the frequency cut off of the filter and the amount of modulation is adjusted.

Filtered synth sound 3 This is a longer sample of a Prophet 5 synth. At first is is like the above sample except a series of notes are played. Towards the end of the sample the resonance is modulated and the LFO speed is adjusted to basically mangle the sound. This shows the level to which the filter can destroy sounds, if that is what you are into.

Drum Sounds

Filtered Drum sound 1 This sound is a simple drum beat with the LFO controlling the frequency cut off. The LFO is set for one cyle every 30 seconds. So , the beginning is silent anf the cut off is slowly raised by the LFO till after 30 seconds the filter is wide open. (not cutting of any frequencies) Note that it is not until half way through the sample before you hear the hi hats , which are at a higher frequency.

Filtered Drum sound 2 This is a longer sample where the LFO speed and amount are adjusted as the same drum beat plays. Subtle to very extreme at the end.


  Other sample sounds of a single oscillator and filter here (near bottom of page)  



Basic concept

The dual filter unit has 2 seperate low pass 4th order filters. These filters can allow low frequencies to pass while stopping higher frequencies from appearing at the output

  The Dual LFOs provide waveforms that are used to modulate the filter parameters.  
  Below Mad Science logo created using text objects  

Mad Science Labs is the outlet of strange and musical ideas of James Gideon

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