# McIntosh C28 Style Preamplifier ## Description McIntosh C28 style audio preamplifier with line-level input stage, active gain and tone control sections, low-impedance output buffer, and dual-rail analog power architecture for classic hi-fi performance with room for modern refinements. ## Project Details - **Owner:** ronichapo - **Created:** 4/23/2026 - **Last Updated:** 4/23/2026 - **Visibility:** Public ## Key Components ### IC1 — [NE5532AP](https://www.flux.ai/adrian95/ne5532ap~hm.md) - Manufacturer Name: Texas Instruments - Package: PDIP-8 - Role Details: Stereo input buffer and gain stage for left and right line-level inputs - Part Type: Integrated Circuit - Manufacturer Part Number: NE5532AP - Role: Input Buffer - License: https://creativecommons.org/licenses/by/4.0/ - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fne5532 **Pins:** - 1IN- [pin 2] - 1IN+ [pin 3] - 1OUT [pin 1] - 2IN- [pin 6] - 2IN+ [pin 5] - 2OUT [pin 7] - VCC- [pin 4] - VCC+ [pin 8] ### IC2 — [NE5532AP](https://www.flux.ai/adrian95/ne5532ap~hm.md) - Package: PDIP-8 - Manufacturer Name: Texas Instruments - Role: Tone Control - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fne5532 - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Integrated Circuit - Role Details: Stereo active Baxandall-style bass and treble control stage - Manufacturer Part Number: NE5532AP **Pins:** - 1IN- [pin 2] - 1IN+ [pin 3] - 1OUT [pin 1] - 2IN- [pin 6] - 2IN+ [pin 5] - 2OUT [pin 7] - VCC- [pin 4] - VCC+ [pin 8] ### IC3 — [NE5532AP](https://www.flux.ai/adrian95/ne5532ap~hm.md) - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fne5532 - License: https://creativecommons.org/licenses/by/4.0/ - Role: Output Buffer - Manufacturer Part Number: NE5532AP - Part Type: Integrated Circuit - Package: PDIP-8 - Manufacturer Name: Texas Instruments - Role Details: Stereo low-impedance output buffer for line outputs **Pins:** - 1IN- [pin 2] - 1IN+ [pin 3] - 1OUT [pin 1] - 2IN- [pin 6] - 2IN+ [pin 5] - 2OUT [pin 7] - VCC- [pin 4] - VCC+ [pin 8] ### IC4 — [NE5532AP](https://www.flux.ai/adrian95/ne5532ap~hm.md) - Package: PDIP-8 - Manufacturer Name: Texas Instruments - Role Details: Reserved dual op-amp for optional filter, balance, loudness, or phono refinement stage - License: https://creativecommons.org/licenses/by/4.0/ - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fne5532 - Part Type: Integrated Circuit - Role: Future Expansion - Manufacturer Part Number: NE5532AP **Pins:** - 1IN- [pin 2] - 1IN+ [pin 3] - 1OUT [pin 1] - 2IN- [pin 6] - 2IN+ [pin 5] - 2OUT [pin 7] - VCC- [pin 4] - VCC+ [pin 8] ### J1 — [RCJ-2221](https://www.flux.ai/adrian95/rcj-2221~dgn.md) - Role: I/O Connector - Manufacturer Part Number: RCJ-2221 - Package: RCA jack - Role Details: Unbalanced audio RCA connector for line-level input or output - License: https://creativecommons.org/licenses/by/4.0/ - Connector Type: Audio / Video Connectors - Manufacturer Name: Same Sky (Formerly CUI Devices) - Part Type: Connector - Datasheet URL: https://www.sameskydevices.com/product/resource/rcj-22.pdf - Connector Gender: Female - Package or Case Code: RCJ2221 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J2 — [RCJ-2221](https://www.flux.ai/adrian95/rcj-2221~dgn.md) - Package: RCA jack - Connector Gender: Female - Package or Case Code: RCJ2221 - Manufacturer Part Number: RCJ-2221 - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Unbalanced audio RCA connector for line-level input or output - Connector Type: Audio / Video Connectors - Role: I/O Connector - Datasheet URL: https://www.sameskydevices.com/product/resource/rcj-22.pdf - Part Type: Connector - Manufacturer Name: Same Sky (Formerly CUI Devices) **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### Q1 — [BC550CBU](https://www.flux.ai/jecstronic/bc550cbu~23e.md) - Manufacturer Part Number: BC550CBU - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Transistor - Manufacturer Name: onsemi - Datasheet URL: https://rocelec.widen.net/view/pdf/wnpm8l45kj/ONSM-S-A0003590719-1.pdf?t.download=true&u=5oefqw - Role Details: Q1 left-channel low-noise input NPN, modern substitute for 2N3565 / BC550C - Role: Low-Level Input Transistor - Package: TO-92 **Pins:** - B [pin 2] - C [pin 1] - E [pin 3] ### Q3 — [BC546BTA](https://www.flux.ai/lcsc/bc546bta~jtca.md) - Manufacturer Part Number: BC546BTA - Package: TO-92 - Part Type: Bipolar Transistors - BJT - JLCPCB Part Class: Extended Part - Role Details: Q3 left-channel input NPN, modern substitute for 2N3392 / BC546B - Package or Case Code: TO-92-3_L4.9-W3.7-P2.54-L - Manufacturer Name: onsemi(安森美) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2410010400_onsemi-BC546BTA_C258143.pdf - Role: Low-Level Input Transistor - Product Info Url: https://lcsc.com/product-detail/Transistors-NPN-PNP_ON-Semicon_BC546BTA_ON-Semicon-ON-BC546BTA_C258143.html - LCSC Part Number: C258143 **Pins:** - B [pin 2] - C [pin 1] - E [pin 3] ### Q5 — [BC639](https://www.flux.ai/lcsc/bc639~j5ld.md) - Role Details: Q5 left-channel driver/output NPN, modern substitute for 2N3392 / BC639 - LCSC Part Number: C2991984 - JLCPCB Part Class: Extended Part - Manufacturer Part Number: BC639 - Package: TO-92 - Part Type: Bipolar Transistors - BJT - Role: Driver Transistor - Package or Case Code: TO-92-3_L4.5-W3.5-P1.27-L - Manufacturer Name: CJ(江苏长电/长晶) **Pins:** - B [pin 3] - C [pin 2] - E [pin 1] ### Q7 — [MJE340G](https://www.flux.ai/lcsc/mje340g~nxeg.md) - Role Details: Q7 left-channel high-voltage NPN, modern substitute for 2N3440 / MJE340 - Package or Case Code: TO-225-3_L7.6-W2.8-P2.54-L - Part Type: Bipolar Transistors - BJT - JLCPCB Part Class: Extended Part - Role: High-Level Output Transistor - Datasheet URL: https://www.lcsc.com/datasheet/lcsc_datasheet_2011181236_onsemi-MJE340G_C898406.pdf - Manufacturer Name: onsemi(安森美) - Manufacturer Part Number: MJE340G - Package: TO-225-3 - Product Info Url: https://lcsc.com/product-detail/Pre-ordered-Products_ON-Semiconductor-ON-MJE340G_C898406.html - LCSC Part Number: C898406 **Pins:** - B [pin 3] - C [pin 2] - E [pin 1] ### VR1 — [PRM162-K420K-103B1](https://www.flux.ai/adrian95/prm162-k420k-103b1~pzx.md) - Part Type: Variable Resistor - Datasheet URL: https://www.bourns.com/docs/Product-Datasheets/PRM16.pdf - Manufacturer Part Number: PRM162-K420K-103B1 - Package: Panel - Package or Case Code: PRM162K415K103B1 - Role: Volume Control - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Dual-gang stereo volume control between input buffer and tone stage - Manufacturer Name: Bourns Inc. **Pins:** - CCW_1 [pin 1] - CCW_2 [pin 4] - CW_1 [pin 3] - CW_2 [pin 6] - MH1 [pin MH1] - MH2 [pin MH2] - WIPER_1 [pin 2] - WIPER_2 [pin 5] ### VR2 — [PRM162-K420K-103B1](https://www.flux.ai/adrian95/prm162-k420k-103b1~pzx.md) - Package or Case Code: PRM162K415K103B1 - Role Details: Dual-gang stereo treble control in active feedback network - Role: Treble Control - Manufacturer Name: Bourns Inc. - License: https://creativecommons.org/licenses/by/4.0/ - Package: Panel - Manufacturer Part Number: PRM162-K420K-103B1 - Datasheet URL: https://www.bourns.com/docs/Product-Datasheets/PRM16.pdf - Part Type: Variable Resistor **Pins:** - CCW_1 [pin 1] - CCW_2 [pin 4] - CW_1 [pin 3] - CW_2 [pin 6] - MH1 [pin MH1] - MH2 [pin MH2] - WIPER_1 [pin 2] - WIPER_2 [pin 5] ### VR3 — [PRM162-K420K-103B1](https://www.flux.ai/adrian95/prm162-k420k-103b1~pzx.md) - Part Type: Variable Resistor - Role Details: Dual-gang stereo bass control in active feedback network - Role: Bass Control - Datasheet URL: https://www.bourns.com/docs/Product-Datasheets/PRM16.pdf - Manufacturer Part Number: PRM162-K420K-103B1 - Package: Panel - Package or Case Code: PRM162K415K103B1 - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: Bourns Inc. **Pins:** - CCW_1 [pin 1] - CCW_2 [pin 4] - CW_1 [pin 3] - CW_2 [pin 6] - MH1 [pin MH1] - MH2 [pin MH2] - WIPER_1 [pin 2] - WIPER_2 [pin 5] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/ronichapo/mcintosh-c28-style-preamplifier~wa](https://www.flux.ai/ronichapo/mcintosh-c28-style-preamplifier~wa).* --- *Generated from [https://www.flux.ai/ronichapo/mcintosh-c28-style-preamplifier~wa](https://www.flux.ai/ronichapo/mcintosh-c28-style-preamplifier~wa)*