Presenting the MacBeth X-Series 'Backend' Filter! I have now departed from using the more common discrete transistor and op-amp based filters that I've used before. This filter and its associated parts have been designed with only passive components and discrete transistors. Why do this? Well I was curious as to what the sound might end up like! The filter is based on the classic design from the past- -both the 'ladder' and the differential amplifier which is part of the resonant feedback loop are now all transistor based as opposed to ladder thru differential amp thru op-amp gain or 'booster' stage. I've used three separate differential amplifiers to tap out the 1 pole, 2 pole and 4 pole responses. The result? The filter is exceptionally clean and noise free- but more so- not only is the bottom end fat and bold, and not only is the high end vibrant and bright- the middle has gained a deeper, wider character! I'm also putting the sound quality down to fact that like the original parts of old- I'm using 5% Tolerance 1/2 Watt Carbon Resistors as opposed to the smaller 1/4 Watt type and the tiny Surface Mount types that are appearing far more frequently in the new analogue synth designs. The capacitors that I'm using are basic ceramic and mylar types. The electrolytic capacitors are of the larger axial kind rather than the more common space saving, radial kind. So it's all kind of 'old school'. Below are some mp3 sound examples that you can hear to judge for yourself... 1. Oscillator 1 from the Dual Oscillator Module- 24dB/octave setting- resonance applied 2. Oscillator 1 from the Dual Oscillator Module -24dB/Octave setting- attack & resonance applied 3. Dual Oscillators that are in unison- then detuned and finally played in a lead fashion 4. Dual Oscillators played high and low, resonant 24dB/Octave filtering. 5. Dual Oscillator Module- 24dB/Octave setting- tight decay on Filter Envelope 6. Dual Oscillator Module- White Noise- 24dB/Octave setting- tight decay on Filter Envelope 7. Dual Oscillator Module with Glide- White Noise- 24dB/Octave setting- tight decay then medium attack sweep on Filter Envelope 'These sounds were recorded without MIDI and were played via the 1V/Octave and Gate Keyboard controller that is currently in development for the X-Series Modular Synthesizer. The Mixer/Filter/Dual VCAs/Dual EGs arrangement is called the 'Backend' because its architecture is similar to the post Oscillator section of some analog synths of days gone by...' 
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