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Radoslav Borisov borissov

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borissov / Micro_Phono_PP500_Preamp.md
Created October 28, 2025 18:30
Enhancing the PP500 Phono Preamp with a Parallel Feedback RC Modification

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

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borissov / keychron_bt_antenna_mod.md
Last active October 29, 2025 07:36
Keychron K8 Bluetooth Fix

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.

Keychrone K8

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.

Keychrone Bluetooth Module

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borissov / beko_pcb_repair.md
Last active August 24, 2024 08:26
E9 PCB repair

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.

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

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borissov / mvcc.js
Created March 9, 2024 19:40
Simple MVCC Example
class MVCCDatabase {
constructor() {
this.data = {};
this.versions = {};
}
async read(key, transactionId) {
// Simulate read operation with MVCC
if (this.versions[key]) {
const version = this.versions[key].find(v => v.transactionId <= transactionId);
@borissov
borissov / bluetooth.md
Last active February 18, 2024 11:50
Bluetooth on old subwoofer

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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borissov / trash.hosts
Last active September 2, 2023 05:55
Аn easy way to block gambling websites. Feel free to add.
127.0.0.1 inbet.com
127.0.0.1 8888.bg
127.0.0.1 palmsbet.com
127.0.0.1 sesame.bg
127.0.0.1 winbet.bg
127.0.0.1 bet365.com
127.0.0.1 efbet.com
127.0.0.1 bwin.com
127.0.0.1 betway.bg
127.0.0.1 betmarketland.bg
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borissov / vim_convert_php_array.vim
Last active January 8, 2020 11:01
Hot key to convert PHP Array to short syntax ([]) exclude build-in functions and work with multiple lines arrays
autocmd FileType php,phtml nmap <buffer><F6> /\%\([a-zA-Z0-9_]\)\@<!\(array\)\( \)*\((\)<CR>ma%r]`adwr[
autocmd FileType php,phtml imap <buffer><F6> <Esc><F6>i
if(window.location.host === 'www.imot.bg'){
document.querySelector('a.next').style.width = '30%';
document.querySelector('a.prev').style.width = '30%';
console.log('cjs working');
}
if(window.location.host === 'www.strava.com'){
function calculateAndAddCalories(htmlString) {
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borissov / bootable_linux_usb.sh
Last active July 19, 2020 09:08
Always forget the commands for creating bootable USB..Burn Linux ISO to USB drive.
#!/bin/bash
sudo fdisk -l
sudo dd bs=4M if=/path/to/iso of=/dev/sdX status=progress && sync
#osx
diskutil list
sudo dd bs=4m if=/path/to/iso of=/dev/sdX && sync
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borissov / opener_for_pgcli_mycli.sh
Created March 6, 2019 07:11
Wrapper to open ".env" files with MyCLI or PgCLI. Search in parent directories.
#!/bin/bash
function dbe() {
local slashes=${PWD//[^\/]/}
local directory="$PWD"
for (( n=${#slashes}; n>0; --n ))
do
if [ -f "$directory/.env" ]; then
echo -e "Load file:\\033[0;31m$(readlink -f -- "$directory/.env") \\033[0m"
while read p; do