# tol s ## Description Preamplificador dual de bajo ruido para contrabajo con dos canales piezo independientes: canal UP con sensor LDTM-028K y canal DOWN con dos LDT0-028K en paralelo, alimentado con batería de 9 V y usando exclusivamente OPA1642. Incluye buffers de entrada de ultra alta impedancia (>=20 MOhm), control de ganancia independiente, filtrado HPF 20-30 Hz y LPF 15-18 kHz, ecualización activa de 3 bandas por canal, protección contra inversión de polaridad, filtrado RF en entradas, desacoplo 100 nF + 10 uF por rail por amplificador, topología de star ground, salidas SMA separadas compatibles con Fishman Presys Blend 301, objetivo de consumo total <5 mA, impedancia de salida <3.5 kOhm, nivel nominal de salida 0.25 V RMS y máximo 1 V RMS sin distorsión. Diseño listo para PCB y fabricación con enfoque de ruido mínimo. ## Project Details - **Owner:** 8rony - **Created:** 3/18/2026 - **Last Updated:** 3/18/2026 - **Visibility:** Public - **Power Requirements:** Batería 9 V, consumo total objetivo <5 mA - **System Architecture:** flowchart TD BT1[9V Battery] --> D1[Reverse Protection] D1 --> VCC[VCC 9V Rail] VCC --> VREFGEN[VREF Divider and Buffer U15] VREFGEN --> VREF[VREF 4.5V] J1[SMA IN UP] --> UPBUF[U1 Input Buffer] UPBUF --> UPGAIN[U2 Gain] UPGAIN --> UPHPF[U3 HPF and Bass EQ] UPHPF --> UPEQ[U4 Mid and Treble EQ] UPEQ --> UPOUT[U5 LPF and Output] UPOUT --> J3[SMA OUT UP] J2[SMA IN DOWN] --> DNBUF[U9 Input Buffer] DNBUF --> DNGAIN[U10 Gain] DNGAIN --> DNHPF[U11 HPF and Bass EQ] DNHPF --> DNEQ[U12 Mid and Treble EQ] DNEQ --> DNOUT[U13 LPF and Output] DNOUT --> J4[SMA OUT DOWN] VCC --> DECOUPLE[Bulk and Local Decoupling] VREF --> UPBUF VREF --> UPGAIN VREF --> UPHPF VREF --> UPEQ VREF --> UPOUT VREF --> DNBUF VREF --> DNGAIN VREF --> DNHPF VREF --> DNEQ VREF --> DNOUT - **Reliability Target (MTBF):** Ruido mínimo, SNR objetivo >=75 dB - **Compliance:** HPF 20-30 Hz, LPF 15-18 kHz, entrada >=20 MOhm, salida <3.5 kOhm, 0.25 V RMS nominal, 1 V RMS máximo sin distorsión - **Role:** Preamplificador dual piezo para contrabajo - **Domain:** Audio analógico de bajo ruido - **Operating Voltage:** 9V - **Role Details:** Canal UP para slap/agudos con LDTM-028K; canal DOWN para graves/cuerpo con 2x LDT0-028K en paralelo; star ground; trazas cortas en nodos de alta impedancia; protección de polaridad; filtro RF; desacoplo 100 nF + 10 uF por rail por OPA1642 - **Manufacturer Part Number:** Primary active device: OPA1642 only ## Key Components ### BT1 — [967](https://www.flux.ai/cherepanyadima/967~d6.md) - Manufacturer Name: Keystone Electronics - Role Details: 9V battery clip input to preamplifier - Manufacturer Part Number: 967 - Datasheet URL: https://www.keyelco.com/userAssets/file/K75p36.pdf - Package: Through Hole - Role: Battery Connector - Part Type: Connectors **Pins:** - NEG [pin NEG] - POS [pin POS] ### D1 — [1N5819HW-7-F](https://www.flux.ai/jecstronic/1n5819hw-7-f~x5v.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Primary series Schottky reverse-polarity protection for 9V battery input - Manufacturer Part Number: 1N5819HW-7-F - Role: Reverse Protection - Package: SOD-123 - Datasheet URL: https://www.diodes.com/assets/Datasheets/ds30217.pdf - Part Type: Diode - Manufacturer Name: Diodes Incorporated **Pins:** - A [pin 2] - K [pin 1] ### D2 — [SP0502BAHT](https://www.flux.ai/kicad-part-library/sp0502baht~nla.md) - Datasheet URL: http://www.littelfuse.com//media/files/littelfuse/technical%20resources/documents/data%20sheets/sp05xxba.pdf - Manufacturer Part Number: SP0502BAHT - Package or Case Code: SOT-23 - Package: SOT-23 - Manufacturer Name: Texas Instruments Inc. - Role Details: ESD clamp for UP input SMA connector - Role: UP Input ESD **Pins:** - A [pin 3] - K [pin 1] - K [pin 2] ### D3 — [SP0502BAHT](https://www.flux.ai/kicad-part-library/sp0502baht~nla.md) - Datasheet URL: http://www.littelfuse.com//media/files/littelfuse/technical%20resources/documents/data%20sheets/sp05xxba.pdf - Package or Case Code: SOT-23 - Role: UP Output ESD - Manufacturer Part Number: SP0502BAHT - Package: SOT-23 - Manufacturer Name: Texas Instruments Inc. - Role Details: ESD clamp for UP output SMA connector **Pins:** - A [pin 3] - K [pin 1] - K [pin 2] ### D4 — [1N5819HW-7-F](https://www.flux.ai/jecstronic/1n5819hw-7-f~x5v.md) - Role: Reverse Protection - Datasheet URL: https://www.diodes.com/assets/Datasheets/ds30217.pdf - Part Type: Diode - Manufacturer Name: Diodes Incorporated - Manufacturer Part Number: 1N5819HW-7-F - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Series Schottky reverse-polarity protection for DOWN-side power entry **Pins:** - A [pin 2] - K [pin 1] ### D5 — [SP0502BAHT](https://www.flux.ai/kicad-part-library/sp0502baht~nla.md) - Package or Case Code: SOT-23 - Role Details: ESD clamp for DOWN input SMA connector - Manufacturer Part Number: SP0502BAHT - Datasheet URL: http://www.littelfuse.com//media/files/littelfuse/technical%20resources/documents/data%20sheets/sp05xxba.pdf - Role: DOWN Input ESD - Manufacturer Name: Texas Instruments Inc. **Pins:** - A [pin 3] - K [pin 1] - K [pin 2] ### D6 — [SP0502BAHT](https://www.flux.ai/kicad-part-library/sp0502baht~nla.md) - Package or Case Code: SOT-23 - Role: DOWN Output ESD - Manufacturer Part Number: SP0502BAHT - Datasheet URL: http://www.littelfuse.com//media/files/littelfuse/technical%20resources/documents/data%20sheets/sp05xxba.pdf - Role Details: ESD clamp for DOWN output SMA connector - Manufacturer Name: Texas Instruments Inc. **Pins:** - A [pin 3] - K [pin 1] - K [pin 2] ### J1 — [SMA-J-P-H-ST-EM1](https://www.flux.ai/jecstronic/sma-j-p-h-st-em1~0a1.md) - Datasheet URL: http://suddendocs.samtec.com/catalog_english/sma.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Connector - Package: Connector - Manufacturer Name: Samtec Inc. - Role Details: SMA_UP input for LDTM-028K - Role: Input Connector - Manufacturer Part Number: SMA-J-P-H-ST-EM1 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J2 — [SMA-J-P-H-ST-EM1](https://www.flux.ai/jecstronic/sma-j-p-h-st-em1~0a1.md) - Datasheet URL: http://suddendocs.samtec.com/catalog_english/sma.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Connector - Role Details: SMA_DOWN input for dual LDT0-028K parallel source - Role: Input Connector - Manufacturer Name: Samtec Inc. - Manufacturer Part Number: SMA-J-P-H-ST-EM1 - Package: Connector **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J3 — [SMA-J-P-H-ST-EM1](https://www.flux.ai/jecstronic/sma-j-p-h-st-em1~0a1.md) - Role Details: SMA_OUT_UP output - Manufacturer Name: Samtec Inc. - Manufacturer Part Number: SMA-J-P-H-ST-EM1 - Package: Connector - Role: Output Connector - Part Type: Connector - Datasheet URL: http://suddendocs.samtec.com/catalog_english/sma.pdf - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J4 — [SMA-J-P-H-ST-EM1](https://www.flux.ai/jecstronic/sma-j-p-h-st-em1~0a1.md) - Part Type: Connector - Package: Connector - License: https://creativecommons.org/licenses/by/4.0/ - Datasheet URL: http://suddendocs.samtec.com/catalog_english/sma.pdf - Manufacturer Part Number: SMA-J-P-H-ST-EM1 - Role Details: SMA_OUT_DOWN output - Manufacturer Name: Samtec Inc. - Role: Output Connector **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### U1 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Manufacturer Name: TI(德州仪器) - Role: UP Buffer - LCSC Part Number: C201728 - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - Role Details: Ultra-high-impedance input buffer for LDTM-028K UP channel - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Package: SOIC-8 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U10 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID - Manufacturer Name: TI(德州仪器) - Role: DOWN Gain - Role Details: Non-inverting gain stage with 1x to 10x range for DOWN channel - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - LCSC Part Number: C201728 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U11 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Role Details: DOWN channel HPF and bass EQ active stage - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Role: DOWN HPF/EQ1 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U12 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Manufacturer Name: TI(德州仪器) - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Role Details: DOWN channel mid and treble EQ active stage - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role: DOWN EQ2 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U13 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role: DOWN LPF/Output - Role Details: DOWN channel final low-pass and output buffer stage - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U14 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - Role: DOWN Spare/Bias Buffer - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role Details: Reserved OPA1642 section for future trim or auxiliary buffering on DOWN side **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U15 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - LCSC Part Number: C201728 - Role: Vref Buffer - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - Manufacturer Name: TI(德州仪器) - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Role Details: Buffered 4.5V midrail reference for both audio channels **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U16 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Role: Supply Monitor/Spare - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Role Details: Reserved OPA1642 section not used in main audio path - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U2 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Role: UP Gain - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Package: SOIC-8 - Role Details: Non-inverting gain stage with 1x to 10x range for UP channel **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U3 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Role: UP HPF/EQ1 - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Package: SOIC-8 - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID - Role Details: UP channel HPF and bass EQ active stage **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U4 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Role: UP EQ2 - Package: SOIC-8 - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID - Role Details: UP channel mid and treble EQ active stage **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U5 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Manufacturer Name: TI(德州仪器) - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - LCSC Part Number: C201728 - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID - Role: UP LPF/Output - Role Details: UP channel final low-pass and output buffer stage - Package: SOIC-8 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U6 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Package: SOIC-8 - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role Details: Reserved OPA1642 section for future trim or auxiliary buffering on UP side - Role: UP Spare/Bias Buffer - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U7 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role Details: OPA1642 dedicado a buffers, ganancia, EQ y salida; único amplificador operacional permitido en el diseño - Manufacturer Part Number: OPA1642AID - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Role: Audio Op-Amp - Manufacturer Name: TI(德州仪器) - LCSC Part Number: C201728 - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Package: SOIC-8 **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U8 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Manufacturer Name: TI(德州仪器) - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - Part Type: Operational Amplifier - LCSC Part Number: C201728 - Package: SOIC-8 - Role Details: OPA1642 dedicado a buffers, ganancia, EQ y salida; único amplificador operacional permitido en el diseño - Role: Audio Op-Amp - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Manufacturer Part Number: OPA1642AID **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] ### U9 — [OPA1642AID](https://www.flux.ai/lcsc/opa1642aid~jev6.md) - Product Info Url: https://lcsc.com/product-detail/Audio-OpAmps_TI_OPA1642AID_OPA1642AID_C201728.html - Manufacturer Part Number: OPA1642AID - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010332_Texas-Instruments-OPA1642AID_C201728.pdf - Role Details: Ultra-high-impedance input buffer for parallel LDT0-028K DOWN channel - Role: DOWN Buffer - Part Type: Operational Amplifier - Package or Case Code: SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL - LCSC Part Number: C201728 - Manufacturer Name: TI(德州仪器) **Pins:** - -INA [pin 2] - +INA [pin 3] - OUTA [pin 1] - V- [pin 4] - V+ [pin 8] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/8rony/tol-s~yf](https://www.flux.ai/8rony/tol-s~yf).* --- *Generated from [https://www.flux.ai/8rony/tol-s~yf](https://www.flux.ai/8rony/tol-s~yf)*