As an ongoing personal project, I am designing and building a custom record player system from the ground up.
The project integrates a regulated ± 20V power supply, RIAA equalized preamplifier, and a 5W Class AB audio amplifier, with the ultimate goal of producing a high-fidelity audio path, from the tonearm needle to the speaker, on a custom PCB.
I began with extensive component research, setting design requirements for both the power supply and audio circuitry. For the power supply, I specified a transformer with 15% voltage headroom and twice the expected current capacity, regulators with >3 V dropout margin and >65 dB ripple rejection, and bulk electrolytics sized at ~2000 µF per ampere with ripple ratings 1.5× the charging current. These ensured stable ±20 V rails with low ripple and noise.
For the audio circuitry, the requirements were that it accurately implement RIAA equalization while achieving at least 40 dB of overall gain from the phono cartridge input through the preamp to the speaker output. Component selection emphasized low-noise devices, RIAA capacitors within ±5% tolerance for equalization accuracy, and an amplifier topology capable of driving an 8 Ω load cleanly with low distortion and sufficient slew rate.
After setting these requirements and selecting components, I transitioned into LTspice. I first modeled each subcircuit individually, verifying their gain, frequency response, and stability. Once validated independently, I combined the modules into a full simulation to confirm that the circuit worked as intended.
Once everything was verified, the next phase was breadboarding, where I prototyped the power supply, preamp, and amplifier on breadboards. After thorough iterative refinement, the breadboarded system was able to successfully amplify the cartridge-level signals up to the speaker level.
Simulation and prototyping confirmed that the design spec was satisfied. For the power supply, the transformer provided 2×24 VAC secondaries, with bulk capacitors sized at 4700 µF per rail (two in parallel for ~9400 µF effective). Ripple Voltage was held far below 0.5 Vpp (sitting at 0.2Vpp), leaving ample margin above the regulators’ >3 V dropout. The LM317/LM337 regulators exhibited >65 dB ripple rejection at 120 Hz, producing clean, stable ±20 V outputs with simulated ripple below 2 mV RMS.
For the audio circuitry, LTspice simulations verified that the RIAA network adhered to the standard 75 µs, 318 µs, and 3180 µs time constants within ±0.3 dB across the 20 Hz–20 kHz band. The audio system achieved a total gain of ~806× (≈58 dB) from the preamp input to the audio amp output. This comfortably exceeded the 40 dB overall gain requirement between cartridge input and speaker output.
With the breadboard validated, I have now began developing a PCB in Altium Designer. I am planning to implement star grounding to isolate noisy and quiet return paths, domain separation between analog and power sections, short, wide traces for high-current rectifier and regulator paths, and compact component layout for the pre-amp network. I am also standardizing connectors using Molex Micro-Fit connectors for the Board to Board interface.
The project is still currently ongoing as I refine the schematic-to-PCB flow and prepare the design for fabrication.
