This appears to be a magnetic phono preamplifier circuit. It’s designed to preamplify the weak signal from a magnetic phono cartridge before feeding it to a main amplifier. Here’s a breakdown of its potential functionalities:
Stages (Possible Configuration):
- Input Transformer (T1): Steps up the weak signal voltage level from a magnetic phono cartridge.
- Input Resistor (R1): Part of a potential voltage divider circuit at the input, influencing impedance and signal level (see note below).
- Input Capacitor (C1): Blocks DC voltage from the cartridge/transformer while allowing the AC audio signal to pass.
- Gain Stage Tube (V1: 12AX7): Amplifies the weak signal from the input transformer.
- Cathode Bypass Capacitor (C2): Improves AC signal fidelity and stability in the gain stage.
- Grid Resistor (R2): Sets the input impedance of the triode section and affects gain.
- Plate Resistor (R3): Along with the grid resistor, sets the gain of the triode amplifier stage.
- Plate Capacitor (C3): Blocks DC voltage from the plate of the triode while allowing the AC audio signal to pass through.
- Output Capacitor (C4): Blocks DC voltage at the output while allowing the AC audio signal to pass. Prepares the signal for the next stage of the amplifier (not shown in this schematic).
Important Notes:
- This is a simplified explanation based on the visible components in the schematic. A complete understanding of the preamplifier’s operation would require the entire circuit diagram and component values.
- The value of the input resistor (R1) might be crucial for proper cartridge loading. Consult the specifications of your specific phono cartridge to determine the recommended load impedance.
- Building a tube circuit requires expertise and knowledge to handle high voltages safely. Always follow a verified and complete schematic diagram for accurate component selection and assembly instructions.
Additional Context from Image:
The text “THAY TJOE SHE 701” on the schematic might not directly correspond to a commercially available brand or model of preamplifier. It’s possible:
- Custom Design: The schematic could represent a custom-designed magnetic phono preamp circuit, potentially built by someone named Thay Tjoe She or a company with that name.
- Internal Design Reference: In some cases, such alpha-numeric codes within schematics might be internal reference designations used by the manufacturer and not indicative of a consumer product name.
