RIAA Phono Preamplifier using LF353N

This phono preamplifier sounds amazing due to its precise RIAA transfer function characteristics with a deviation of only ±0.4 dB. My friend Rufus bought many expensive preamplifiers to go with his Oracle Delphi turntable but he just was not able to find anything that would give him the sharp treble and low bass he wanted. Therefore, I decided to build this because the problem with many expensive and cheap preamplifiers is that they fix the frequency response at the 20 Hz to 20 kHz range, and therefore using a high-end cartridge with a frequency response of 10 Hz to 25 kHz, just does not do it any justice. This preamplifier circuit provides a -3 dB frequency response of 10 Hz to 65 kHz, which is useful as many cartridges have much higher upper range.

For this circuit, I am using the LF353N dual operational amplifier IC, which has wide bandwidth and good frequency response. The JFET input impedance alone is 10,000,000,000,000 Ω, which allows us to connect the cartridge coil directly to the gate junction without requiring a decoupling capacitor that would otherwise reduce the sound accuracy. Thefore this circuit has only a 220 Ω resistor (R1) in the signal path. The input sensitivity of this circuit is 2.3 mV for every 47,000 Ω, making it ideal for moving magnet (MM), and high output moving coil (MC) cartridges.

The 5600 pF and 1600 pF capacitors are extremely small values and they may prove difficult to source, however many online electronics shops sell them. You can also look for 5.6 nF, and 1.6 nF, which can be found readily, however, the output capacitor has to be a metalized polyester film type if you want the best performance.

This circuit requires a split rail power supply for the operational amplifier IC, and this can be a down side as it is expensive to build, but worth the effort if you want great sound.

I have kept the build as simple as possible with minimum number of cuts to the tracks. You will need a 37-track × 47-hole strip-board for this build, and it is a standard size available online. Although I have listed the basic components, the rest such as connectors, and chip socket, is up to your discretion. Back in the 90s, it cost me less than ten pounds to build it, however today; you might need to see the bank manager due to inflation. If you click on the image, you will be able to see a clearer enlarged version that you can follow when building it.

There are four cuts under the LF353N IC, and using a chip socket will allow you to run a ground link from under the socket, otherwise you can always have a wire loop going over the IC. As you can see, the circuit is almost symmetrical around the vertical axis, but not entirely due to the IC pinout not being symmetrical. The component numbering is identical for both channels, which makes building simple.

Components