Printed Circuit Board # 8
AWA Universal Classic Moving Magnet Phono Preamplifier
(PC Board Only)
The “AWA Universal Classic Moving Magnet Phono Preamplifier PC Board” is designed for the do-it-yourself audio enthusiast who has an advanced knowledge of vacuum tube electronics and low-level circuitry layout. With this board, you can build several varieties of moving-magnet phono stages from classic designs (C22, 7c, SP3), or use it to construct your own circuit design. The circuit consists of 2 voltage gain stages, and a cathode follower for each channel to drive the input of your line-level preamp (using dual-triode tubes such as 12AX7, 12AU7, 7025, ECC82, & ECC83). There are ample component footprints to allow for many NFB RIAA network designs, as well as footprints for cartridge loading resistance and capacitance.
The voltage gain tubes have common filament wiring (F1, F2, F3), whereas the cathode follower (V3) has separate filament connections (F4, F5, F6) for biasing it to a positive voltage as required in several designs, and may be wired for either 6.3V or 12.6V.
Each tube has a separate B+ high voltage supply terminal (V1=E3, V2=E4, V3=E5) such that each stage may be supplied its own operating voltage if desired. This PC board requires an external power supply. AWA sells several power supply boards that may be used with this preamp; a single regulated high-voltage power supply board, or a board specifically designed for this project, with 2 regulated filament supplies, and 2 regulated B+ supplies, incorporating on-board power transformers. The builder may also copy the power supply used in a classic design.
The PCB was laid out to fit 1/2-watt resistors in low level areas, and larger sizes where a higher power resistor is required. The supplied database gives component values for the classic 7c, C22 and SP3a preamplifiers; it’s up to the builder to select the component grade used. The capacitor footprints are large enough to accommodate many “audio-grade” capacitors. The layout of this board is such that it minimizes crosstalk between channels, and results in a good-sounding phono preamp that will satisfy the most demanding “vinyl enthusiast”.
This project is designed for the advanced DIYer, and should only be attempted if you understand the fundamentals of vacuum tube electronics, layout of low-level circuitry, and possess the ability to fabricate a metal chassis.
PCB #8 is being offered in the AWA Store for $ 30.00 including shipping to a US address. If you wish an AWA Member discount or require shipping to non-US address, please request a quote using the form at the bottom of this page.
A detailed description of the PCB #8 preamplifier project is available by clicking on the button to the right.
This offering is for the bare PCB only and additional components are required.
PCB Info Help
If you have any questions, contact the staff at AWAHelpDesk@antiquewireless.org.
To request an AWA Membership discount or shipping information for Non-US shipping, utilize the form below. Be sure to specify the PCB Item # and the quantity of each board in your request.