Building McIntosh C28

2:51

Looking into schematic components.

Analyzing the schematic.

Looking for "Left channel low level stage BOM only: list Q1 Q3 Q5 Q7, R19 through R49, R85 R86, and capacitors associated with the left low level stage with exact values, types, and any substitute part notes." in C28_BOM_DIY-%D7%A8%D7%A9%D7%99%D7%9E%D7%AA-%D7%A8%D7%9B%D7%99%D7%91%D7%99%D7%9D-%D7%9E%D7%9C%D7%90%D7%94-%D7%A7%D7%9C%D7%95%D7%93-98ffbe6a-0b85-41a0-b472-e4da1fb9a5fd.xlsx

Looking for "Left channel low level stage only: extract transistor designators, resistor designators and values, capacitor designators and values, and exact connectivity or signal flow for the left channel." in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Searching for components.

Finished searching for components.

Looking for "For the LEFT channel only, list exact connections to Q1: what connects to base, collector, and emitter, including resistor and capacitor designators and numbered nodes." in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Looking for "For the LEFT channel only, list exact connections to Q3: what connects to base, collector, and emitter, including resistor and capacitor designators and numbered nodes." in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Looking for "For the LEFT channel only, list exact connections to Q5 and Q7: what connects to each base, collector, and emitter, including resistor and capacitor designators and numbered nodes." in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Looking for "For the LEFT channel only, list every numbered interface node 24 25 28 29 30 31 32 and 1 2 3 4 5 6 7 8 with the components directly attached to each node." in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Thinking deeply about your request.

Planning preamplifier rebuild.

Clarifying project documents.

Creating a high-level plan.

Working on your request.

Analyzing the schematic.

Evaluating circuit inspections.

Working on your request.

Searching the project.

Searching for assets and documents.

Searching 2 domains.

Looking for project assets.

Searching 2 domains.

Search complete — 50 results across 2 domains.

Preparing implementation details.

Outlining the requirements process.

I've made a plan, and started work on it.
5 days

Started implementing a plan

#Goal

- Rebuild the left-channel low-level stage of the McIntosh C28 preamplifier by removing the modern NE5532-based front end and replacing it with the discrete, transistor-based topology derived from the uploaded low-level-stage PDF and BOM spreadsheet.

#Implementation plan

1. Analyze the Current Schematic

1. Locate the existing left-channel NE5532 op-amp based circuitry in the current project.

2. Identify and mark the components that conflict with the desired C28 discrete stage.

2. Remove or Isolate Conflicting Circuitry

1. Remove or isolate the modern left-channel structure to prevent interference with the new design.

3. Integrate C28-Derived Left-Channel Stage

1. Refer to the uploaded low-level-stage PDF and BOM spreadsheet to identify all specific components, specifically the discrete transistors (e.g., Q1, Q3, Q5, Q7) and their supporting resistors and capacitors.

2. Add the identified discrete components into the project schematics for the left-channel low-level stage.

3. Wire the added components according to the connectivity and topology shown in the reference documents.

4. Verification and Documentation

1. Review the updated left-channel schematic for correctness against the C28 reference, ensuring that all connections and part values match the BOM.

2. Document the changes made, explaining the transition from the modern NE5532 circuitry to the discrete C28-based left-channel stage.

#Success criteria

- All conflicting modern op-amp components in the left-channel are removed or isolated.

- The discrete transistor-based left-channel low-level stage is accurately built according to the provided PDF and BOM, with correct parts and wiring.

- The schematic reflects a faithful C28-derived left low-level discrete stage ready for production.

5 days

Task completed.

0:19

5 days

Execution stopped due to insufficient credits.

6:52

Accessing knowledge base.

Looking for "left channel low level stage Q1 Q3 Q5 Q7 R19 R21 R23 R25 R27 R29 R31 R33 R35 R37 R39 R41 R43 R45 R47 R49 C7 C9 C11 C13 C15 C17 C18 values and substitutions" in C28_BOM_DIY-%D7%A8%D7%A9%D7%99%D7%9E%D7%AA-%D7%A8%D7%9B%D7%99%D7%91%D7%99%D7%9D-%D7%9E%D7%9C%D7%90%D7%94-%D7%A7%D7%9C%D7%95%D7%93-98ffbe6a-0b85-41a0-b472-e4da1fb9a5fd.xlsx

Started: analyzing schematic and extracting left-stage parts

Searching for components.

Finished searching for components.

Looking for "left channel exact wire connections for R19 R21 R23 R25 R27 R29 R31 R33 R35 R37 R39 R41 R43 R45 R47 R49 C7 C9 C11 C13 C15 C17 C18" in low-level-stage-48f8121a-6ea7-4e91-8ff5-f365059467f1.pdf

Analyzing the schematic.

5 days

Execution stopped due to insufficient credits.

5:31

Analyzing the schematic.

5 days

No changes applied.

0:04

5 days

Applied changes.

nets {

net unnamed = C24:P2;

net unnamed = VR2:CW_2;

net unnamed = J1:3, J2:3, C4:P2;

net unnamed = C24:P1;

net unnamed = IC2:2OUT;

net unnamed = R10:P1, IC2:1OUT;

net unnamed = R6:P2;

net unnamed = C16:P1, IC3:VCC-, IC4:VCC-;

net unnamed = C27:P1;

net unnamed = C7:P2;

net unnamed = IC3:VCC+, IC4:VCC+;

net unnamed = IC2:1IN-;

net unnamed = VR1:CCW_1, GND:GND, VR3 CCW_2 - R16 P2:GND, VR2:CCW_1, R4 P2 - J2 1:GND, J2:1, C16:P2;

net unnamed = R10:P2;

net unnamed = VR1:CW_1;

net unnamed = IC2:VCC+;

net unnamed = R4:P2;

net unnamed = R4:P1;

net unnamed = C4:P1;

net unnamed = R14:P1;

net unnamed = J2:2;

net unnamed = VR2:WIPER_1;

net unnamed = IC2:1IN+;

net unnamed = VR1:CW_2;

net unnamed = C27:P2;

net IN_L = J1:2;

net unnamed = R11:P2;

net unnamed = VR1:WIPER_2;

net unnamed = C22:P2;

net unnamed = IC2:2IN+;

net unnamed = C11:P1;

net unnamed = IC2:VCC-;

net unnamed = R3:P1;

net unnamed = IC2:2IN-;

net unnamed = C17:P1;

net unnamed = IC3:2IN-;

net unnamed = VR2:WIPER_2;

net unnamed = C11:P2;

net IN_R = J1:1;

net unnamed = VR1:CCW_2;

net unnamed = VR2:CW_1;

net unnamed = C7:P1;

net unnamed = IC3:2OUT;

net unnamed = R11:P1;

net unnamed = R6:P1;

net unnamed = IC3:2IN+;

net unnamed = R3:P2, IC3:1IN-;

net unnamed = C22:P1;

net unnamed = IC3:1OUT;

net unnamed = R14:P2;

net unnamed = VR1:WIPER_1;

net unnamed = VR2:CCW_2;

net unnamed = R13:P1;

net unnamed = IC3:1IN+;

net unnamed = R13:P2;

net unnamed = C17:P2;

}

5 days

Applied changes.

5 days

0:07

I hit an issue removing the old front end in one large batch, so I am decomposing the edit into smaller verified steps and continuing with the C28 rebuild.
5 days

Applied changes.

5 days

Applied changes.

5 days

Added 28 components

0:07

Added 1x BC550CBU as Q1 (Pins: C, B, E)

Added 1x BC546BTA as Q3 (Pins: B, E, C)

Added 1x BC639 as Q5 (Pins: B, E, C)

Added 1x MJE340G as Q7 (Pins: E, B, C)

Added 17x Generic Resistor as R19, R21, R23, R25, R27, R29, R31, R33, R35, R37, R39, R41, R43, R45, R47, R49, R85 (Pins: P2, P1)

Added 7x Generic Capacitor as C7, C9, C11, C13, C15, C17, C18 (Pins: P1, P2)

5 days

R9 P2 - IC2 1IN-
IC2 1OUT - R9 P1
R7 P2 - IC3 2IN-
R9 P2 - IC2 1IN-
IC2 2OUT - R11 P1
IC2 1OUT - R9 P1
R12 P2 - IC2 2IN-
IC2 2OUT - R11 P1
R11 P2 - IC2 2IN-
R10
Resistance
22kΩ
R11
Resistance
22kΩ
R9
Resistance
22kΩ
R8
Resistance
10kΩ
R12
Resistance
22kΩ
VR3 CCW_2 - R16 P2


  • Ground
    A common return path for electric current. Commonly known as ground.
  • Net Portal
    Wirelessly connects nets on schematic. Used to organize schematics and separate functional blocks. To wirelessly connect net portals, give them same designator. #portal
  • Power Net Portal
    Wirelessly connects power nets on schematic. Identical to the net portal, but with a power symbol. Used to organize schematics and separate functional blocks. To wirelessly connect power net portals, give them the same designator. #portal #power
  • Generic Resistor
    A generic fixed resistor ideal for rapid circuit topology development. Its footprint automatically adapts based on the selected package case code—supporting 0402, 0603, 0805, 1203, and many other standard SMD packages, as well as axial horizontal and vertical configurations. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard resistor values: 1.0 ohm, 10 ohm, 100 ohm, 1.0k ohm, 10k ohm, 100k ohm, 1.0M ohm 1.1 ohm, 11 ohm, 110 ohm, 1.1k ohm, 11k ohm, 110k ohm, 1.1M ohm 1.2 ohm, 12 ohm, 120 ohm, 1.2k ohm, 12k ohm, 120k ohm, 1.2M ohm 1.3 ohm, 13 ohm, 130 ohm, 1.3k ohm, 13k ohm, 130k ohm, 1.3M ohm 1.5 ohm, 15 ohm, 150 ohm, 1.5k ohm, 15k ohm, 150k ohm, 1.5M ohm 1.6 ohm, 16 ohm, 160 ohm, 1.6k ohm, 16k ohm, 160k ohm, 1.6M ohm 1.8 ohm, 18 ohm, 180 ohm, 1.8K ohm, 18k ohm, 180k ohm, 1.8M ohm 2.0 ohm, 20 ohm, 200 ohm, 2.0k ohm, 20k ohm, 200k ohm, 2.0M ohm 2.2 ohm, 22 ohm, 220 ohm, 2.2k ohm, 22k ohm, 220k ohm, 2.2M ohm 2.4 ohm, 24 ohm, 240 ohm, 2.4k ohm, 24k ohm, 240k ohm, 2.4M ohm 2.7 ohm, 27 ohm, 270 ohm, 2.7k ohm, 27k ohm, 270k ohm, 2.7M ohm 3.0 ohm, 30 ohm, 300 ohm, 3.0K ohm, 30K ohm, 300K ohm, 3.0M ohm 3.3 ohm, 33 ohm, 330 ohm, 3.3k ohm, 33k ohm, 330k ohm, 3.3M ohm 3.6 ohm, 36 ohm, 360 ohm, 3.6k ohm, 36k ohm, 360k ohm, 3.6M ohm 3.9 ohm, 39 ohm, 390 ohm, 3.9k ohm, 39k ohm, 390k ohm, 3.9M ohm 4.3 ohm, 43 ohm, 430 ohm, 4.3k ohm, 43K ohm, 430K ohm, 4.3M ohm 4.7 ohm, 47 ohm, 470 ohm, 4.7k ohm, 47k ohm, 470k ohm, 4.7M ohm 5.1 ohm, 51 ohm, 510 ohm, 5.1k ohm, 51k ohm, 510k ohm, 5.1M ohm 5.6 ohm, 56 ohm, 560 ohm, 5.6k ohm, 56k ohm, 560k ohm, 5.6M ohm 6.2 ohm, 62 ohm, 620 ohm, 6.2k ohm, 62K ohm, 620K ohm, 6.2M ohm 6.8 ohm, 68 ohm, 680 ohm, 6.8k ohm, 68k ohm, 680k ohm, 6.8M ohm 7.5 ohm, 75 ohm, 750 ohm, 7.5k ohm, 75k ohm, 750k ohm, 7.5M ohm 8.2 ohm, 82 ohm, 820 ohm, 8.2k ohm, 82k ohm, 820k ohm, 8.2M ohm 9.1 ohm, 91 ohm, 910 ohm, 9.1k ohm, 91k ohm, 910k ohm, 9.1M ohm #generics #CommonPartsLibrary
  • Generic Capacitor
    A generic fixed capacitor ideal for rapid circuit topology development. You can choose between polarized and non-polarized types, its symbol and the footprint will automatically adapt based on your selection. Supported options include standard SMD sizes for ceramic capacitors (e.g., 0402, 0603, 0805), SMD sizes for aluminum electrolytic capacitors, and through-hole footprints for polarized capacitors. Save precious design time by seamlessly add more information to this part (value, footprint, etc.) as it becomes available. Standard capacitor values: 1.0pF, 10pF, 100pF, 1000pF, 0.01uF, 0.1uF, 1.0uF, 10uF, 100uF, 1000uF, 10000uF 1.1pF, 11pF, 110pF, 1100pF 1.2pF, 12pF, 120pF, 1200pF 1.3pF, 13pF, 130pF, 1300pF 1.5pF, 15pF, 150pF, 1500pF, 0.015uF, 0.15uF, 1.5uF, 15uF, 150uF, 1500uF 1.6pF, 16pF, 160pF, 1600pF 1.8pF, 18pF, 180pF, 1800pF 2.0pF, 20pF, 200pF, 2000pF 2.2pF, 22pF, 220pF, 2200pF, 0.022uF, 0.22uF, 2.2uF, 22uF, 220uF, 2200uF 2.4pF, 24pF, 240pF, 2400pF 2.7pF, 27pF, 270pF, 2700pF 3.0pF, 30pF, 300pF, 3000pF 3.3pF, 33pF, 330pF, 3300pF, 0.033uF, 0.33uF, 3.3uF, 33uF, 330uF, 3300uF 3.6pF, 36pF, 360pF, 3600pF 3.9pF, 39pF, 390pF, 3900pF 4.3pF, 43pF, 430pF, 4300pF 4.7pF, 47pF, 470pF, 4700pF, 0.047uF, 0.47uF, 4.7uF, 47uF, 470uF, 4700uF 5.1pF, 51pF, 510pF, 5100pF 5.6pF, 56pF, 560pF, 5600pF 6.2pF, 62pF, 620pF, 6200pF 6.8pF, 68pF, 680pF, 6800pF, 0.068uF, 0.68uF, 6.8uF, 68uF, 680uF, 6800uF 7.5pF, 75pF, 750pF, 7500pF 8.2pF, 82pF, 820pF, 8200pF 9.1pF, 91pF, 910pF, 9100pF #generics #CommonPartsLibrary
  • Generic Inductor
    A generic fixed inductor suitable for rapid circuit topology development. The footprint automatically adapts based on the selected package, supporting standard SMD sizes (e.g., 0402, 0603, 0805) as well as well-known inductor packages such as SDR1806, PA4320, SRN6028, and SRR1260. Standard inductor values: 1.0 nH, 10 nH, 100 nH, 1.0 µH, 10 µH, 100 µH, 1.0 mH 1.2 nH, 12 nH, 120 nH, 1.2 µH, 12 µH, 120 µH, 1.2 mH 1.5 nH, 15 nH, 150 nH, 1.5 µH, 15 µH, 150 µH, 1.5 mH 1.8 nH, 18 nH, 180 nH, 1.8 µH, 18 µH, 180 µH, 1.8 mH 2.2 nH, 22 nH, 220 nH, 2.2 µH, 22 µH, 220 µH, 2.2 mH 2.7 nH, 27 nH, 270 nH, 2.7 µH, 27 µH, 270 µH, 2.7 mH 3.3 nH, 33 nH, 330 nH, 3.3 µH, 33 µH, 330 µH, 3.3 mH 3.9 nH, 39 nH, 390 nH, 3.9 µH, 39 µH, 390 µH, 3.9 mH 4.7 nH, 47 nH, 470 nH, 4.7 µH, 47 µH, 470 µH, 4.7 mH 5.6 nH, 56 nH, 560 nH, 5.6 µH, 56 µH, 560 µH, 5.6 mH 6.8 nH, 68 nH, 680 nH, 6.8 µH, 68 µH, 680 µH, 6.8 mH 8.2 nH, 82 nH, 820 nH, 8.2 µH, 82 µH, 820 µH, 8.2 mH #generics #CommonPartsLibrary
  • Terminal
    Terminal
    An electrical connector acting as reusable interface to a conductor and creating a point where external circuits can be connected.
  • RMCF0805JT47K0
    47 kOhms ±5% 0.125W, 1/8W Chip Resistor 0805 (2012 Metric) Automotive AEC-Q200 Thick Film #forLedBlink
  • 875105359001
    10uF Capacitor Aluminum Polymer 20% 16V SMD 5x5.3mm #forLedBlink #commonpartslibrary #capacitor #aluminumpolymer #radialcan
  • CTL1206FYW1T
    Yellow 595nm LED Indication - Discrete 1.7V 1206 (3216 Metric) #forLedBlink

McIntosh C28 Style Preamplifier

McIntosh C28 Style Preamplifier thumbnail
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.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$29.45–$31.02

Digi-Key

$47.25–$48.66

LCSC

$46.14–$46.36

Mouser

$54.75

TME

$6.42

Verical

$25.14–$40.11

Controls