18 thoughts on “Build An Analog Filter For $10

    1. A circuit without ICs is named “discrete”, ICs are just micro circuits composed of transistors, resistors, capacitors. For instance the TL072 which is a commonly used chip comports two operational amplifiers, each amplifier composed of 16 transistors, so 32 transistors for the whole chip. You could do a discrete TL072 but it would take nearly 100 solders for the transistors VS 8 pin to solder for the chip.

  1. I haven't looked at the actual schematics here, but the presence of ICs certainly does not mean it must be a digital circuit.

    There is a whole category of ICs that simply contain multiples of a regular analogue component. (eg an 8 pin IC that contains 4 completely seperate resistors). Or there are heaps of types of ICs that contain a small, commonly used circuit design, such as an op-amp. (for example a 347 IC op-amp contains 4, completely seperate, operational amplifier circuits in one neat package)

    1. Most IC’s are analog functions within. I build analog Drums and Synths all the time. IC format is a must for not having a build take up massive amounts of space or become to unworldly in matching transistors, etc.

  2. Regarding the misconception about ICs not being analog. There are two categories of analog circuits: discrete and integrated. A discrete circuit is built from individually packaged transistors, FETs, etc. Discrete analog circuits are generally regarded as being higher quality, with unique character, because the designer was probably intimately familiar with every aspect of the circuit. However, there was also plenty of crappy gear made with discrete analog.

    The other category of analog circuits involves IC's (chips), such as the familiar opamps, OTAs, etc. These are more convenient and compact to work with, and don't necessarily mean lower quality than discrete analog. Most commercial analog gear from the mid 70's til now uses ICs. Including highly regarded stuff like Moogerfooger… and it is surface mount as well. I would also like to end the misconception that surface mount is inherently sonically inferior.

  3. Regarding the misconception about ICs not being analog. There are two categories of analog circuits: discrete and integrated. A discrete circuit is built from individually packaged transistors, FETs, etc. Discrete analog circuits are generally regarded as being higher quality, with unique character, because the designer was probably intimately familiar with every aspect of the circuit. However, it is certainly possible to make crappy gear with discrete analog.

    The other category of analog circuits involves IC's (chips), such as the familiar opamps, OTAs, etc. These are more convenient and compact to work with, and don't necessarily mean lower quality than discrete analog. Most commercial analog gear from the mid 70's til now uses ICs.

    Vacuum tube (valve) circuits are also considered discrete.

  4. Probably opAmps. Analogue signal processing depends strongly on active filters that can be designed with OpAmps + passive circuit elements. Integrators, differentiators, etc all need opAmps, and it is efficient to build it around these instead of using transistors, given the near-ideal characteristics of opAmps (near-infinite input impedance. near-0 output impedance, etc. etc.)

  5. When I first started getting into DIY synth, one of my first thoughts was "wtf are all these chips doing in analog gear?" Now I know better, but yeah, it's counterintuitive.

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