Amplifier Circuit DiagramsAudio Circuit DiagramsPower Supplies

Multimedia RIAA Preamplifier Schematic Circuit Diagram

Preserving Vinyl Treasures: The Challenge of CD Availability

While some album titles once exclusive to vinyl are gradually making their way onto CDs, the transition is far from comprehensive. If you possess cherished vinyl records you wish to transfer to CDs, two key factors come into play. Firstly, CD preservation is simpler than safeguarding vinyl records, and secondly, the decline of turntables, even in fully-equipped Hi-Fi systems, is evident. Considering the realm of software and PCs, converting from vinyl to CD poses no significant hurdle. A plethora of programs, both paid and freeware, are readily accessible. These tools facilitate the remastering of vinyl records, albeit with varying levels of success, and effectively eliminate unwanted noise like pops and crackles.

Navigating the Sound Card Dilemma in Vinyl-to-CD Conversion

In this digital transition, these programs operate through your PC’s sound card. Herein lies a challenge. Most high-quality turntables feature a magnetic cartridge that typically delivers a low signal of a few mV. This cartridge signal necessitates specific frequency correction known as RIAA correction. While seasoned readers might recall RIAA’s significance, those from the CD generation might be unfamiliar with the term, possibly associating it with illegal music downloading on the internet.

Multimedia RIAA Preamplifier Schematic Circuit Diagram

Understanding RIAA Correction and Preamplifier Sensitivity

The intricate process of vinyl engraving necessitates high-boost frequency correction, adhering to the precise curve defined by the RIAA. Referred to as RIAA correction, this correction boosts lower frequencies, a task reversed by the magnetic cartridge’s preamplifier. However, this correction makes the preamplifier exceptionally sensitive to undesirable noises, including those from the mains power supply. Careful attention to grounding and shielding is crucial for the success of this project.

Simplified Preamplifier Design and Impedance Matching

The preamplifier’s schematic simplicity lies in its use of a low-noise dual operational amplifier, specifically the NE5532. Components like R7, R8, C8, and C9 are meticulously chosen to closely match the RIAA correction curve. With an impedance of 47 kΩ, tailored to magnetic cartridges, and a gain of 35 dB at 1,000 Hz, the preamplifier can deliver the few hundred mV output typically required by PC sound card line inputs.

Shielded Wiring and Power Supply Options

To avoid hum issues, shielded wiring between the cartridge and the amplifier is crucial. The assembly is best housed in a metal casing linked to an electrical ground. Regarding power supply, three options are presented. A purist might opt for a noise-free 9-V battery, eliminating components outlined with dotted lines. Alternatively, utilizing the PC’s 12 V positive voltage through a Y-connector offers a more elegant solution, albeit with occasional signal noise. Finally, connecting a 12 V mains adapter to the +12-volt point in the drawing provides additional filtering, ensuring enhanced performance for audiophiles.


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