DM4LX

RIAA Preamp

Sep. 2019

RIAA preamp based on tubeland.de design (full kit available here) with balanced XLR driver.

Most components are already in my inventory, so I ordered only the bare PCB. I selected time constant critical capacitors within 1% tolerance with a LCR meter.

For the balanced XLR driver I chose LM833 low-noise audio op-amps.

The wiring was replaced with proper shielded coax cable (which I had to buy first, RG213 was too big 😉) for better noise performance:

Idle output noise dropped from 660 µV RMS to a little bit below 200 µV RMS (measurement bandwidth 10 Hz...100 kHz). The nominal output level is 1,55 V RMS which results in 78 dB SNR.