The Samsung K4B2G1646F is a 2Gb DDR3L SDRAM memory component designed for high-speed performance, offering data rates up to 1866Mb/sec/pin. Available in a 96-ball FBGA package and organized as 128Mb x 16 I/Os x 8 banks, it is optimized for use in various applications requiring efficient data storage and retrieval. The device supports both 1.35V (DDR3L) and 1.5V (standard DDR3) power supplies, ensuring compatibility with a wide range of system requirements. Key features include an 8-bit pre-fetch architecture, programmable CAS latency, on-die termination (ODT), and internal self-calibration through the ZQ pin. The component also adheres to JEDEC standards and is compliant with RoHS, ensuring it is free of lead and halogen. Suitable for commercial and industrial temperature ranges, the K4B2G1646F offers robust performance for various demanding applications.

This project is a Smart Thermostat design using an ESP32 module for WiFi connectivity and a BME680 sensor for environmental monitoring. The user interface includes an E-ink display and an encoder for settings adjustment. Power is managed through a USB-C connector with a 3.3V regulator. #referenceDesign #project #ESP32 #ESP32WROOM #RF #WIFI #MCU #thermostat #referenceDesign #edge-computing #edgeComputing #espressif #template #reference-design

This is a reference design of the Bluetooth Low-Energy (BLE) temperature sensor. It uses an ESP32-MINI-1 microcontroller to connect to an SHT31-DIS-B2.5KS sensor. The sensor can be powered through connector J15, and additional components provide voltage regulation and derbiaising. Temperature data can be accessed via BLE. #referenceDesign #simple-embedded #espressif #template #reference-design

This is a reference design of the Bluetooth Low-Energy (BLE) temperature sensor. It uses an ESP32-MINI-1 microcontroller to connect to an SHT31-DIS-B2.5KS sensor. The sensor can be powered through connector J15, and additional components provide voltage regulation and derbiaising. Temperature data can be accessed via BLE. #referenceDesign #simple-embedded #espressif #template #reference-design

This document provides a detailed guide to building a relay circuit that uses a Raspberry Pi to control a buzzer. The relay acts as a switch, allowing the Raspberry Pi to turn the buzzer ON and OFF through GPIO pins.

Small, inexpensive AI pendant. Records sound after user presses a button. Indicate behavior with RGB LED. Onboard processing and cloud connectivity through mobile phone tethering.

Short for GPAD by the Public Invention is a general purpose alarm device (with software) as a module for medical devices (and others). It is based on the Arduino Uno Atmega328 design and may similarly become extensible through headers and shields. #internetOfThings #smartHomeDevices

This is a LoRa-based door and window sensor incorporating a microcontroller unit (MCU). It features a reed sensor, LED indicators, a AAA non-rechargeable battery, and a booster IC for constant voltage. The MCU is linked to peripherals through nets, ensuring optimal performance #LoRa #MCU #ReferenceDesign #project #referenceDesign #simple-embedded #seeed #seeed-studio #template #reference-design

This project is a TCS3200D-TR color sensor circuit utilizing resistors, capacitors, LEDs, a JST connector, and a transistor for control. The color sensor allows for precise color identification and its output is accessible through a JST connector. #industrialSensing #colorSensor #referenceDesign #osramusa #template #reference-design

This is a Garage Security System Reference Design, employing a Photon microcontroller to process sensor triggers, signaling through a buzzer and LEDs, powered by an HLK-PM03 power supply. #referenceDesign #edge-computing #edgeComputing #particle #template #iot #system #security

10kΩ, Through Hole Trimmer Potentiometer 0.5W Side Adjust Bourns, PV36X mpn = 3296W-1-201

A semiconductor light source that emits light when current flows through it.

10kΩ, Through Hole Trimmer Potentiometer 0.5W Side Adjust Bourns, PV36X mpn = 3296W-1-201

Bipolar (BJT) Transistor NPN 230V 15A 30MHz 150W Through Hole TO-3P(L) #CommonPartsLibrary #TransistorBJT #2SC5200

Through Hole straight socket strip, 01x20, 2.54mm pitch, single row #connector #pinsocket #tht

"This is what makes time travel possible." —Doc Brown In order to travel through time, the vehicle integrated with the flux capacitor needed to be traveling at 88 mph (140.8 km/h), and required 1.21 gigawatts of power (1,210,000,000 watts)

Time-to-Digital converter plug-on module (shield) for Raspberry Pi B+. The board utilizes a TDC7200 (TI) with a time resolution of ~50ps. The Start/Stop inputs to the TDC can be configured with JP2 from either external signals or coming from the RPi's GPIO5 pin in case a timing signal is present at this pin from another plug-on board on the same RPi. Start and Stop signals can be configured from different signals (coming from the input connectors) or the same source (setting "common" on JP3) either supplied from the Start input connector or GPIO5. Read-out of the TDC chip is done through the RPi's SPI bus.

GCT_USB4105_REVA USB-C (USB TYPE-C) USB 2.0 Receptacle Connector 24 (16+8 Dummy) Position Surface Mount, Right Angle; Through Hole In Stock None Global Connector Technology None https://pricing.snapeda.com/search/part/USB4105/?ref=eda USB4105 Aliases: undefined

Through hole straight pin header, 1x04, 4 pin, 4-pin, horizontal, angled, 2.54mm pitch, 6mm pin lenght single row

This project is a Smart Thermostat design using an ESP32 module for WiFi connectivity and a BME680 sensor for environmental monitoring. The user interface includes an E-ink display and an encoder for settings adjustment. Power is managed through a USB-C connector with a 3.3V regulator. #referenceDesign #project #ESP32 #ESP32WROOM #RF #WIFI #MCU #thermostat #referenceDesign #edge-computing #edgeComputing #espressif #template #reference-design

The Junior line-following robot, equipped with photoresistors and an operational amplifier, is capable of detecting and following lines with precision. This compact and efficient robot uses photoresistors to capture contrast information on the ground and, through the operational amplifier, quickly processes this data to adjust its trajectory. It's an ideal tool for introducing students to the world of robotics and engineering. // El robot seguidor de línea Junior, equipado con fotoresistencias y un amplificador operacional, es capaz de detectar y seguir líneas con precisión. Este robot compacto y eficiente utiliza las fotoresistencias para captar la información de contraste en el suelo y, mediante el amplificador operacional, procesa rápidamente estos datos para ajustar su trayectoria. Es una herramienta ideal para introducir a estudiantes en el mundo de la robótica y la ingeniería.

The HOTCHIP HT4936S is a sophisticated mobile power management integrated circuit designed by Hotchip, optimized for portable power solutions that require efficient charging and power management capabilities. This advanced component integrates features for charging and discharging through a common port, automatic load detection for boost startup and shutdown, four-light battery level indication, and a low battery alert functionality. The HT4936S stands out for its ability to manage 1A input/output with minimal external components, leveraging synchronous rectification to enhance efficiency and reduce thermal footprint. Additionally, it supports a versatile charging protocol accommodating both 4.20V and 4.35V batteries, and is packaged in a compact SOP16 form factor, ensuring a low-cost, space-efficient solution for a wide range of mobile power applications including power banks, backup power supplies, and lithium battery chargers. It incorporates protection features against battery overcharge, over-discharge, and thermal overload, thereby ensuring reliable operation across a range of conditions. Furthermore, the HT4936S facilitates direct LED drive and includes an NTC thermistor input for temperature monitoring, making it an all-encompassing solution for power management in consumer electronics.

This is a reference design of the Bluetooth Low-Energy (BLE) temperature sensor. It uses an ESP32-MINI-1 microcontroller to connect to an SHT31-DIS-B2.5KS sensor. The sensor can be powered through connector J15, and additional components provide voltage regulation and derbiaising. Temperature data can be accessed via BLE. #referenceDesign #simple-embedded #espressif #template #reference-design

"This is what makes time travel possible." —Doc Brown In order to travel through time, the vehicle integrated with the flux capacitor needed to be traveling at 88 mph (140.8 km/h), and required 1.21 gigawatts of power (1,210,000,000 watts)

Sensor using through hole LDR and power with SMT LED Resistors and PZT3904

This project is a Smart Thermostat design using an ESP32 module for WiFi connectivity and a BME680 sensor for environmental monitoring. The user interface includes an E-ink display and an encoder for settings adjustment. Power is managed through a USB-C connector with a 3.3V regulator. #referenceDesign #project #ESP32 #ESP32WROOM #RF #WIFI #MCU #thermostat #referenceDesign #edge-computing #edgeComputing #espressif #template #reference-design

A passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. See https://en.wikipedia.org/wiki/Inductor

Through Hole straight pin header, 01x04, 2.54mm pitch, single row #connector #pinheader #tht

This project is a Battery Management System (BMS) built around STMicroelectronics' STC3115AIQT battery monitor IC. It uses I2C for communication, features alarm management, and supports battery charging. The power supply, battery connection points, and debug interface are facilitated through connectors. #project #Template #charger #monitor #reusable #module #batterycharger #template #bms #STC3115 #stm

3 Position Wire to Board Terminal Block Horizontal with Board 0.197" (5.00mm) Through Hole #screwblock #connector #commonPartsLibrary

"This is what makes time travel possible." —Doc Brown In order to travel through time, the vehicle integrated with the flux capacitor needed to be traveling at 88 mph (140.8 km/h), and required 1.21 gigawatts of power (1,210,000,000 watts)

Here is a simple USB powered lamp that can be used to light your desktop during power failures. The circuit operates from the 5 Volt available from the USB port. The 5V from the USB port is passed through current limiting resistor R2 and transistor Q1. The base of transistor Q1 is grounded via R1 which provides a constant bias voltage for Q1 together with D2. The diode D1 prevents the reverse flow of current from battery. C1 is used as a noise filter. Two white LED’s are used here for the lamp, you can also use a 2 V torch bulb instead of LED’s. LED D3 indicates connection with USB port.

This is an NFC card that works from the solar. On the board, there are two solar panels that accumulate energy through the controller in the supercapacitor. The NFC controller itself can be programmed via the microcontroller on the board #solar #nfc #stm32 #iot

A semiconductor light source that emits light when current flows through it.

This project is a TCS3200D-TR color sensor circuit utilizing resistors, capacitors, LEDs, a JST connector, and a transistor for control. The color sensor allows for precise color identification and its output is accessible through a JST connector. #industrialSensing #colorSensor #referenceDesign #osramusa #template #reference-design

"This is what makes time travel possible." —Doc Brown In order to travel through time, the vehicle integrated with the flux capacitor needed to be traveling at 88 mph (140.8 km/h), and required 1.21 gigawatts of power (1,210,000,000 watts)

This project is a reference design for the VCNL3040 sensor interfaced via I2C. It includes a VCNL3040 ambient light sensor, a voltage regulator (AP2112K-3.3TRG1), an I2C level shifter using BSS138 MOSFETs, and necessary support components. Circuit interfaces through a JST connector. All components are powered by a 3.3V power source. #referenceDesign #industrialsensing #vishay #template #reference-design

Sensor using through hole LDR and power with SMT LED Resistors and PZT3904

This is an Energy Meter project leveraging an ATTiny85 microcontroller (U1) to sense current through an ACS712 module (U2). It displays the data in real-time on an OLED display (OLED1) and interacts with three buttons (NEXT, MENU, OK). This compact energy meter is suitable for edge computing and low-power Internet of Things (IoT) applications #project #keypad #arduino #attiny85 #ISP #referenceDesign #edge-computing #edgeComputing #microchip #template #reference-design

Connector Header Through Hole 2 position 0.079" (2.00mm) 01x02 JST B2B PH K

This is an Energy Meter project leveraging an ATTiny85 microcontroller (U1) to sense current through an ACS712 module (U2). It displays the data in real-time on an OLED display (OLED1) and interacts with three buttons (NEXT, MENU, OK). This compact energy meter is suitable for edge computing and low-power Internet of Things (IoT) applications #project #keypad #arduino #attiny85 #ISP #referenceDesign #edge-computing #edgeComputing #microchip #template #reference-design

sEMG-DAQ is a wearable 6 channel data acquisition unit for capturing surface electromyographic (sEMG) signals from human arm muscles using SJ2-3593D jack connectors while conditioning, digitizing, processing and transmitting them as sEMG data to an external AI accelerated board through an SM12B-SRSS IDC connector where AI models are run for various applications including robotic control, muscle signals medical assessment and gesture recognition. The board leverages an INA125P instrumentation amplifier together with filter stages utilizing LM324QT op-amps for conditioning and an STM32G4A1VET6 microcontroller for the digitization, processing and data transmission of the signals. Since AI models can only be as good as the data, the design of such a DAQ is necessary to ensure clean, reliable and real-time data for AI applications requiring sEMG data. The board also has USB-FS and JTAG to cater for debugging. The power (5V) is fed through a screw terminal and is regulated by two LDK320AM LDO regulators to offer 5V, 3.3V and 1.8V to meet the requirements of various components on the board.

Datasheet-driven MFRC522 RFID reader PCB intended to replicate RC522 module behavior at 13.56 MHz with a 3.3 V nominal supply, 2.5 V to 3.3 V operating range, and RC522-style 8-pin host header compatibility. The MFRC522 datasheet is the authoritative source for pin usage, power rail relationships, oscillator requirements, reset/IRQ handling, and antenna interface topology. AVDD, DVDD, and TVDD must be tied to the same 3.3 V rail; PVDD must be equal to or lower than DVDD; unused MFIN must be tied to SVDD or PVSS; SVDD must be tied to a valid supply if not used independently. The design must use a 27.12 MHz crystal meeting CL 10 pF and ESR <= 100 ohms, local 100 nF decoupling on each MFRC522 supply grouping plus bulk capacitance, and an RF front-end based on the MFRC522 application diagram and reference reader matching/tuning network. PCB priorities are short crystal and RF connections, compact placement of decoupling capacitors at supply pins, solid ground reference, and protected antenna region with minimal digital routing through the RF area.

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TECHNICAL ASSIGNMENT AND DESIGN GUIDE Active Three-Way Crossover on NE5532 Powered by AM4T-4815DZ and Amplifiers TPA3255 (Updated Version) 1. GENERAL PURPOSE OF THE DEVICE The goal of the development is to create an active three-way audio crossover for one channel of a loudspeaker system, working with the following drivers: LF: VISATON W250 MF: VISATON MR130 HF: Morel MDT-12 Each frequency range is amplified by a separate power amplifier: LF: TPA3255 in PBTL mode (mono) MF + HF: second TPA3255 in stereo mode (one channel for MF, the other for HF) The crossover accepts a single linear audio signal (mono) and divides it into three frequency bands: Range Frequency Range LF 0 – 650 Hz MF 650 – 2500 Hz HF 2500 Hz and above Filter type: Linkwitz–Riley 4th order (24 dB/oct) at each crossover point (650 Hz and 2500 Hz). The crossover must provide: minimal self-noise; no audible distortion in the audible range; stable operation with NE5532 at ±15 V power supply; easy adjustment of the level for each band, as well as the overall level (via the input buffer). 2. FILTER TYPES AND BASIC OPERATING PRINCIPLES Each filter is implemented as two cascaded Sallen–Key 2nd order (Butterworth) stages, resulting in a final 4th order LR4 filter. Topology: non-inverting Sallen–Key, optimal for NE5532. For all stages: Cascade gain: K ≈ 1.586 This provides a Q factor of 0.707 (Butterworth), which in combination gives a Linkwitz–Riley 4th order. 3. COMPONENT VALUES FOR FILTERS 3.1 Universal Parameters RC chain capacitors: 10 nF, film capacitors, tolerance ≤ 5% Resistors: metal-film, tolerance ≤ 1% The gain of each stage is set by feedback resistors: Rf = 5.9 kΩ Rg = 10 kΩ K ≈ 1 + (Rf / Rg) ≈ 1.59 The circuit should allow for the installation of a small capacitor (10–47 pF) in parallel with Rf (footprint provided) for possible stability correction (not mandatory to install in the first revision). 3.2 650 Hz Filters (Low-frequency boundary for MF) These are used for the division between W250 and MR130. LP650 — Low-frequency Filter 2nd Order R1 = 24.9 kΩ R2 = 24.9 kΩ C1 = 10 nF C2 = 10 nF Two stages: LP650 #1 and LP650 #2. HP650 — MF High-frequency Filter 2nd Order Same values: R1 = 24.9 kΩ R2 = 24.9 kΩ C1 = 10 nF C2 = 10 nF Two stages: HP650 #1 and HP650 #2. 3.3 2500 Hz Filters (Upper boundary for MF) These are used for the division between MR130 → MDT-12. LP2500 — High-pass MF Filter R1 = 6.34 kΩ R2 = 6.34 kΩ C1 = 10 nF C2 = 10 nF Two stages: LP2500 #1 and LP2500 #2. HP2500 — High-frequency Filter Same values: R1 = 6.34 kΩ R2 = 6.34 kΩ C1 = 10 nF C2 = 10 nF Two stages: HP2500 #1 and HP2500 #2. 4. OPERATIONAL AMPLIFIERS The NE5532 (dual op-amp, DIP-8 or SOIC-8) is used. A minimum of 4 packages (8 channels) for filters: NE5532 Function U1A, U1B LP650 #1, LP650 #2 (LF) U2A, U2B HP650 #1, HP650 #2 (Lower MF cut-off) U3A, U3B LP2500 #1, LP2500 #2 (Upper MF cut-off) U4A, U4B HP2500 #1, HP2500 #2 (HF) Additionally: U5 — input buffer / preamplifier (both channels) If necessary, an additional NE5532 (U6) for the balanced input (see section 6.2). All NE5532 should have local decoupling for power supply (see section 5.1). 5. CROSSOVER POWER SUPPLY AM4T-4815DZ DC/DC module is used: Input: 36–72 V, connected to the 48 V power supply for TPA3255 amplifiers. Output: +15 V / –15 V, up to 0.133 A per side. Maximum output capacitance: ≤ 47 µF per side (according to the datasheet). 5.1 Power Filtering Input (48 V): RC variant (simpler, acceptable for the first revision): R = 1–2 Ω / 1–2 W C = 47–100 µF (for 63 V or higher) LC variant (preferred for improved noise immunity): L = 10–22 µH C = 47–100 µF The developer may implement LC if confident in choosing the inductance and its parameters. Output +15 V and –15 V (general filtering): Electrolytic capacitor 10–22 µF per side 100 nF (X7R) per side to GND Local decoupling for NE5532 (REQUIRED): For each NE5532 package: 100 nF between +15 V and GND 100 nF between –15 V and GND Place as close as possible to the op-amp power pins (short traces). Additional local filtering for power lines: For each NE5532, decouple from the ±15 V main rails: Either 4.7–10 Ω resistor in series with +15 V and –15 V, Or ferrite bead in each rail. After this component, place local capacitors (100 nF + 1–4.7 µF) to ground. 6. INPUT TRACT: INPUTS, BUFFER, ADJUSTMENT 6.1 Unbalanced Input (RCA / Jack / Linear) The main mode is the unbalanced linear input, for example, RCA. Input tract structure: RF-filter and protection: Signal → series resistor Rin_series = 100–220 Ω After resistor — capacitor Cin_RF = 470–1000 pF to GND This forms a low-level RF filter and reduces high-frequency noise. DC-block (low-pass HP-filter): Capacitor Cin_DC = 2.2–4.7 µF film in series Resistor to ground Rin_to_GND = 47–100 kΩ Cut-off frequency — negligible in the audio range but removes DC. Input buffer / preamplifier (NE5532, U5): Non-inverting configuration. Input — after DC-block. Gain: adjustable, e.g., Rg_fixed = 10 kΩ (to GND through trimmer) Rf = 10–20 kΩ + footprint for trimmer (e.g., 20 kΩ) The gain should be in the range of 0 dB to +10…+12 dB. Possible configuration: Rg = 10 kΩ fixed Rf = 10 kΩ + 10 kΩ trimmer in series. This allows adjusting the overall level of the crossover according to the source and amplifier levels. Buffer output: A low-impedance output (after NE5532) This signal is simultaneously fed to the inputs of all filters: LP650 (LF) HP650 → LP2500 (MF) HP2500 (HF) 6.2 Balanced Input (XLR / TRS) — Optional, but laid out on the board The board should allow for a balanced input, even if it’s not used in the first revision. Implementation requirements: XLR/TRS connector (L, R, GND) or separate 3-pin header. Simple differential receiver on NE5532 (extra U6 package or use one channel of U5 if sufficient). Circuit: classic instrumentation amplifier or differential amplifier: Inputs: IN+ and IN– Output — single-ended signal of the same level (or slightly amplified), fed to DC-block and buffer (or directly to the buffer if integrated). Switching between balanced/unbalanced mode: Implement using jumpers / bridges or adapters: Either switch before the buffer, Or use two separate pads, one of which is unused. All balanced input grounds must be connected to the same AGND point as the unbalanced input to avoid ground loops. 7. LEVEL ADJUSTMENT OF BANDS (BEST METHOD) The level adjustment of each band (LOW, MID, HIGH) is required to match the sensitivity of the speakers and amplifiers. Recommended method: After each full filter (after LP650×2, MID-chain HP650×2 → LP2500×2, HP2500×2), install: A passive attenuator: Series: Rseries (0–10 kΩ, adjustable) Shunt: Rshunt to GND (10–22 kΩ, fixed or adjustable) For simplicity and reliability: Implementation on the board: For each band (LOW, MID, HIGH) provide: Pad for multi-turn trimmer 10–20 kΩ as a divider (between signal and ground) in the "level adjustment" configuration. If adjustment is not needed — install a fixed divider (two resistors) or simply use a jumper. It is preferable to use: For setup: multi-turn trimmers 10–20 kΩ, available on the top side of the board. Nominals for the initial configuration can be selected through measurements, but the PCB should have flexibility. This provides: Accurate balancing of band volumes without interfering with the filters; Flexibility for fine-tuning to the specific characteristics of the speakers. 8. INPUTS AND OUTPUTS OF THE CROSSOVER (FINAL) 8.1 Inputs 1× Unbalanced linear input (RCA or 3-pin header) 1× Balanced input (XLR/TRS or 3-pin header) — optional, but space must be provided on the board. Input impedance (unbalanced after RF-filter): 22–50 kΩ. The input tract must be implemented using shielded cables. 8.2 Outputs Outputs to amplifiers: Output Signal LOW OUT After LP650×2 (LF) MID OUT After HP650×2 → LP2500×2 (MF) HIGH OUT After HP2500×2 (HF) Each output: Series resistor 100–220 Ω (prevents possible oscillations and simplifies cable management). A nearby own AGND pad (ground output), so the signal pair SIG+GND runs together. Outputs should be compactly placed on 2-pin connectors (SIG+GND) or 3-pin (SIG+GND+reserve). 9. PCB DESIGN REQUIREMENTS 9.1 Board Number of layers: 2 layers Bottom layer: solid analog ground (AGND). 9.2 Component Placement Key principles: RC chains of each filter (R1, R2, C1, C2, Rf, Rg) should form a compact "island" around the corresponding op-amp. If elements are placed too far apart, the filter will not work correctly (calculated frequency and Q will shift). Feedback tracks (Rf and Rg) should be as short and direct as possible. The AM4T-4815DZ module should be placed: Far from the input buffer, Far from the first filter stages, If necessary, make a "cutout" in the ground under it to limit noise propagation. Place the input connector, RF-filter, and buffer on one side of the board, and the output connectors on the opposite side. 9.3 Ground The entire audio circuit uses one analog ground: AGND. Connect AGND to the power ground (48 V and amplifiers) at one point ("star"). The star should be implemented as: One point/pad where: The ground of the input, The ground of the filters, The ground of the outputs, The ground of the DC/DC. Avoid long narrow "ground" jumpers — use wide polygons with a single connection point. 9.4 Placement of Output Connectors Group LOW/MID/HIGH compactly. Each should have its own GND pad nearby. Route the SIG+GND pairs as signal pairs, avoiding large loops. 10. ADDITIONAL ELEMENTS: PROTECTION, TEST POINTS 10.1 Test Points (TP) Be sure to provide test points (pads): TP_IN — crossover input (after buffer) TP_LOW — LF filter output TP_MID — MF filter output TP_HIGH — HF filter output TP_+15, TP_–15, TP_GND — power control This greatly simplifies debugging with an oscilloscope. 10.2 Power Protection On the 48 V input — it is advisable to provide: Diode/scheme for reverse polarity protection (if possible), TVS diode or varistor for voltage spikes (optional). 10.3 Possible Stability Correction Pads for small capacitors (10–47 pF) in parallel with Rf in buffers and, if necessary, in some stages — in case of stability issues (this can be not installed in the first revision, but footprints should be provided). 11. BILL OF MATERIALS (BOM) Operational Amplifiers: NE5532 — 4 pcs (filters) NE5532 — 1–2 pcs (input buffer and balanced input) Total: 5–6 NE5532 packages. Resistors (1%, metal-film): 24.9 kΩ — 8 pcs 6.34 kΩ — 8 pcs 10 kΩ — ≥ 12 pcs (feedback, buffers, etc.) 5.9 kΩ — 8 pcs 22 kΩ — 1–2 pcs (input, auxiliary chains) 47–100 kΩ — several pcs (DC-block, input) 100 kΩ — 1 pc (if needed) 100–220 Ω — 4–6 pcs (outputs, RF, protection) 4.7–10 Ω — 2 pcs for each op-amp or group of op-amps (power filtering) — quantity to be clarified during routing. Trimmer Resistors: 10–20 kΩ multi-turn — one for each band (LOW, MID, HIGH) 10–20 kΩ — 1–2 pcs for the input buffer (overall gain adjustment). Capacitors: 10 nF film — 16 pcs (RC filters) 2.2–4.7 µF film — 1–2 pcs (input DC-block) 10–22 µF electrolytic — 2–4 pcs (DC/DC outputs) 1–4.7 µF (X7R / tantalum) — 1 pc for local power filtering (optional). 100 nF ceramic X7R — 10–20 pcs (local decoupling for each op-amp) 470–1000 pF — 1–2 pcs (RF filter on the input) 10–47 pF — optional for stability correction (Rf). Power Supply: AM4T-4815DZ — 1 pc Inductor 10–22 µH (if LC filter) — 1 pc R 1–2 Ω / 1–2 W — 1 pc (if RC filter). Connectors: Input (RCA + 3-pin for internal input) Balanced (XLR/TRS or 3-pin header) Outputs LOW/MID/HIGH — 2-pin/3-pin connectors. 12. TESTING RECOMMENDATIONS 12.1 First Power-up Apply ±15 V without installed op-amps. Check with a multimeter: +15 V –15 V No short circuits in the power supply. Install the op-amps (NE5532). Apply a sine wave of 100–200 mV RMS (signal generator). Check with an oscilloscope at TP: LP650 — should pass LF and roll off everything above 650 Hz. HP650 — should roll off LF, pass everything above 650 Hz. LP2500 — should roll off above 2500 Hz. **HP250 0** — should pass everything above 2500 Hz. 12.2 Phase Check The Linkwitz–Riley 4th order should give a flat frequency response when summed at the crossover points. This can be verified with REW/Arta. 12.3 Noise Check If there is noticeable "shshsh" or whistling: Check: Grounding layout (star) Placement and filtering of AM4T-4815DZ Presence and proper installation of all 100 nF and local filters. 13. FINAL RECOMMENDATIONS FOR BEGINNERS Do not rush, build the circuit step by step: input → buffer → one filter → test, then continue. Check component values at least twice before soldering. Filters should be routed as compact "islands" around the op-amp, do not stretch R and C across the board. Always remember the rule: "The feedback trace should be as short as physically possible." Before ordering the PCB, make a "paper prototype": print at 1:1, cut it out, place real components to check everything fits.