RIAA Preamp Circuit Design

Here is an RIAA preamp circuit design for a magnetic cartridge using the Mitsubishi M5218 IC. This project also shows a DIY build that anyone can follow to make his or her own preamplifier. The op amp IC came from a salvaged board; however, there is still some old stock online. You can also use the NJM4558 IC, which is very cheap on eBay (ten for a pound). Although I have not tried it, almost any general-purpose frequency compensated op-amp IC has a chance of working in this circuit. You can also use an op amp with FET input in which case you will not require C3. As well as an active filter network within the feedback loop, there are also passive networks at the input and output to further "fine tune" the RIAA equalisation.

An advantage of this circuit is that it uses standard capacitor values that are cheaply and readily available. The two capacitors in the feedback loop may prove difficult to source but they are available if you search for them in different ways. For example, 0.0056 µF / 5.6 nF / 5600 pF are the same and sellers often list them in different ways. All else failing, you can always connect multiple capacitors together to make up the value.

To build this, you will need a strip-board with 36-tracks × 48-holes. Some ready-cut ones online are 36-tracks × 50-holes (95 mm × 127 mm), which could work. In this design, I am leaving plenty of room so that there is space if your capacitors turn out to be different size. As you can see, the build is almost symmetrical about the vertical axis; however, the IC pinout is not and therefore there are some subtle differences around the op amp inputs and output.

Components

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