Radoslav Borisov borissov

Optimizing Gain and Power Supply Noise

The PP500 phono preamplifier, built around the JRC4580 op-amp, originally uses 3.3 kΩ resistors and 4.7 µF capacitors in the feedback network. While this design is stable, it can result in a lower output level when used with medium-output MM cartridges such as the Audio-Technica AT3600L, and the stock power section is highly susceptible to interference.

To optimize both the gain and power filtration, a comprehensive modification was applied. In the feedback network, after iterative testing with different values (1 kΩ, 2 kΩ, and 2.5 kΩ), a 4.7 kΩ resistor in parallel was selected as the perfect sweet spot—balancing high clarity with the necessary volume output. This was combined with an upgraded 10 µF capacitor to optimize the low-frequency response and ensure proper RIAA correction.

Significant improvements were also made to the power supply stage to eliminate noise. The stock 1000 µF filtering capacitor was replaced with a much larger 2200 µF unit, byp

The PP500 phono preamplifier, built around the JRC4580 op-amp, originally uses 3.3 kΩ resistors and 4.7 µF capacitors in the feedback network. While this design is stable, it can result in a lower output level when used with medium-output MM cartridges such as the Audio-Technica AT3600L.

To increase the gain and improve the low-frequency response, a parallel RC modification was applied. In this case, a 1.5 kΩ resistor in parallel with the original 3.3 kΩ resistor, combined with a 10 µF capacitor in series, was added. This effectively adjusts the feedback loop, increasing the overall gain while maintaining the low-frequency cutoff around 10 Hz, ensuring

After prolonged use and numerous issues with the Keychron K8 in Bluetooth mode, I concluded that the problem was entirely hardware-related after exhausting all possible software solutions.

Upon opening the keyboard, I noticed that the Bluetooth module was placed in a highly unsuitable location—sandwiched between the aluminum case on top and the battery underneath. This positioning severely impacted signal strength, leading to frequent connection drops and input issues.

To improve connectivity, I decided to relocate the antenna by extending it using a blue wire from a Cat6 Ethernet cable, which was the best option available at the time. While the wire’s dimensions and properties might not be ideal, a Wi-Fi antenna from an old laptop or router would likely be a better choice.

After encountering error E9 (a problem with the locking mechanism) on my Beko washing machine, I replaced the locking mechanism, but the error persisted. Upon further investigation, I concluded that the issue was with the main control board. After removing the board and conducting a visual inspection, I discovered charred components. I ordered a new T2 transistor and new R21 and R50 resistors. After replacing the locking mechanism and the components on the board, the machine is working like new again.

![Added new T2 transistor and new R21 and R50](https://gist.github.com/user-attachments/assets/21794909-9d09-4062-b171-f

PARTS LIST:

Bluetooth Audio Receiver [XY-BT-Min]

The Bluetooth Audio Receiver is a versatile device designed to facilitate wireless audio streaming from various compatible devices such as smartphones, tablets, and laptops. By leveraging Bluetooth technology, it enables seamless connectivity and high-quality audio transmission, eliminating the need for cumbersome cables. This receiver is perfect for upgrading conventional wired audio systems to modern wireless setups, offering enhanced convenience and flexibility in audio configurations.

DC-DC Power Module [B0505S-1W]

The B0505S-1W 5V to 5V Converter DC-DC Power Module is a specialized power conversion solution featuring ground noise isolation capabilities. It efficiently converts a 5V input voltage to a stable 5V output while effectively isolating ground noises, ensuring clean and reliable power delivery. This module is particularly valuable in applications where noise interference can degrade system performance, such as audio equipment, sensit

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