HIFI preamp XA-100 PCB board
XA-100 series pre-amplifier board
A100 series board, the circuit structure is a fully symmetrical diamond-shaped differential circuit, the sound characteristic is sweet. Based on the A100 series pre-amplifier boards, the XA-100PRE series pre-amplifier boards are now being launched.
It can be used as a single-ended signal amplification, can be used as a smooth signal amplification, and can be used as a voltage drive stage for pure post-amplification.
The size of the board is: length 18CM, width 15CM
2. Power supply situation: The board does not contain a power supply. When using an external power supply, the motherboard needs 8 regulated power supplies for independent power supply. With the ground wire, there are a total of five sets of terminals, which can be directly crimped with a screwdriver. The voltage used is as follows:
(1) If the pre-stage signal is amplified:
Main power supply voltage: ±24V,
The auxiliary voltages are: ±15V1, ±15V2, respectively for the left and right channel buffer voltage,
Secondary voltage: ±15V, voltage for servo operational amplifier.
(2) Voltage drive stage as a pure post-amplification circuit:
Main power supply voltage: ±45V,
The auxiliary voltages are: ±15V1, ±15V2, respectively, for the left and right channel buffer voltages,
Secondary voltage: ±15V, voltage for servo operational amplifier.
Supporting power supply board link: XA-100PRE PSU, the connection between the amplifier board and the power supply is shown in the figure:
3. Regarding volume control:
(1) Traditional voltage divider type volume control circuit can be used, generally the volume potentiometer is connected before the input signal. The wiring diagram is as follows:
(2) Using parallel shunt volume control circuit, you can connect the volume potentiometer before the input signal, or connect the volume potentiometer to the signal output terminal. The wiring diagram is as follows:
4. Introduction to the use of components:
The triode uses the European very low-noise audio dedicated tubes, BC550 and BC560 from Philip Holland, each pair of tubes has been strictly tested and matched, and the matching accuracy is within 1%. The field tube is K170\J74, which have been strictly tested and matched. The accuracy is within 0.5%, and the decoupling capacitor is Nichicon FG plus RIFA film capacitor, and the sound is extremely clear and transparent.
5. Board use:
(1) It can be used as a single-ended signal amplification. This is the default usage and the board does not need to be changed.
(2) It can be used as a smooth signal amplification. In this application, several resistors need to be changed. Specific installation instructions can be provided.
(3) It can be used as a pure post-voltage drive stage (supports single-ended and stable two modes), and specific installation instructions can be provided.