Transistor Ladder

A-120 24dB Low Pass Filter

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The A-120 module is – the name “Low Pass 1” suggests it – something like the “mother of all Doepfer filters” (from a historical perspective, not from a technical perspective). The circuit is based on the famous 24 dB Moog transistor cascade (“ladder” filter). And this is actually the official mother of all synthesizer filters. … Read more

A-108 6/12/24/48dB Low Pass Filter

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Like the A-120, the A-108 filter is also based on the Moog transistor cascade, but uses not only 4 poles, but 8 and can therefore have a maximum slope of 48 dB. That sounds sensational at first, but in real synthesizer life it’s not that extremely spectacular. What is striking, however, is the fantastic and … Read more