Discrete All-Transistor RIAA-Equalized MM Phono Preamplifier 2.

The discrete RIAA-equalized preamp project is based on the phono input stage of a vintage Sansui 8080DB/9090DB stereo receiver. The stereo receiver uses an obsolete BA312 chip; however, it can easily be modified to preserve the distinctive sound quality of the original design.

Internal to the BA312 is the first transistor that functions as a common emitter gain amplifier, while the subsequent Darlington-pair transistors further amplify the signal with high current gain.

To improve the S/N ratio of the preamp, five identical gain KSC1845 are paralleled. The Darlington pair transistors are also low-noise KSC1845. The RIAA network is connected from the emitter of the first transistor to the collector of the Darlington pair. All film capacitors used have a polypropylene dielectric. The resistors are all metal film with 1% tolerance.

A simple capacitance multiplier circuit was added at the preamp's power supply to further improve the audio quality of the preamp. This also ensures a lower noise level and reduced harmonic distortion while at the same time maintaining the receiver's classic sound signature.

The prototype was tested with four moving magnet phono cartridges: Gemini HDCN-15 Audio-Technica AT-XP3, Goldring E2, and AT-VM95E. Each cartridge was alternately mounted into a Sony direct drive PS-T3 turntable.

In conclusion, we appreciate your interest in the series about the RIAA-equalized moving magnet phono cartridge preamplifiers. We hoped you enjoyed watching the preamp projects that have been created and presented in this series.
BuildAudioAmps acknowledges you for sharing your comments throughout the series. We hoped that the knowledge we have shared will inspire you to learn more about high-fidelity audio reproduction.
"Like a broken record," BuildAudioAmps will keep on building audio-related projects.

[jim]

Looks like ~2nv/rt Hz or the equivalent noise of 200 ohm resistor. Perfect transistor matching with five 1845's should be around 1.4nv (3dB better or ~150r). ie The two quietest ones are doing all the heavy lifting, higher Hfe, lower Vbe.
Nice project! It would be interesting to try MPSA06 or 2N4403 (PNP)...
Also, your at the equivalent noise of two paralleled LM4562's 👍 {below vinyl surface noise}

[robertkovar]

switching DC-DC XL6009 (400kHz) for phono is act of brutality, :) you need low noise power supply - linear (capacitive multiplier or shunt )