| Component | Value | Voltage Rating | Quantity | | :--- | :--- | :--- | :--- | | Resistor (R1) | 47kΩ (Input) | 1/4W | 2 | | Resistor (R2) | 100kΩ (Cin to GND) | 1/4W | 2 | | Resistor (R3) | 560Ω (Feedback to GND) | 1/2W | 2 | | Resistor (R4) | 47kΩ (Feedback loop) | 1/4W | 2 | | Resistor (R5) | 10Ω (Zobel) | 2W | 2 | | Resistor (R6) | 2.2Ω (Output inductor parallel) | 2W | 2 | | Capacitor (C1) | 1.8µF (Input coupling) | 50V (Film) | 2 | | Capacitor (C2) | 100pF (Feedback compensation) | 50V (Ceramic) | 2 | | Capacitor (C3) | 0.1µF (Zobel) | 100V (Polyester) | 2 | | Capacitor (C4) | 100µF (Bootstrap) | 100V (Electrolytic) | 2 | | Inductor (L1) | 1µH (Air core, 10 turns) | N/A | 2 |
Beware of Fakes: The STK411-210E is heavily counterfeited. Authentic Sanyo modules have a deep gray, textured epoxy back and laser-etched text (not painted). Fakes often use a shiny black resin and have rounded pins.
If you cannot find an original STK411-210E:
| Problem | Likely Cause | Fix | |-----------------------|---------------------------------------|------------------------------| | Oscillation (>10MHz) | Missing Zobel network or long outputs | Add 10Ω+100pF to ground | | Hum/buzz | Ground loop | Star ground, short inputs | | DC on output (>50mV) | Failed feedback cap (C_fb) | Replace 100µF electrolytic | | Thermal shutdown | Insufficient heatsink | Increase heatsink size, fan | | Low gain | Wrong feedback resistor values | Set Rf1/Rf2 = 22k/1k | stk411-210e circuit diagram
| Model | Power (6 Ω) | Voltage | THD | Package | |-----------|-------------|---------|-------|---------------| | STK411-110E| 2 × 15 W | ±22 V | 0.4% | Thin SIP-12 | | STK411-210E | 2 × 30 W | ±28 V | 0.4% | Thin SIP-12 | | STK411-310E| 2 × 40 W | ±32 V | 0.4% | Thin SIP-12 | | STK412-150E| 2 × 50 W | ±35 V | 0.08% | Thick SIP-12 |
The 210E is ideal for 30W/ch into 6Ω or 25W/ch into 8Ω.
Left Channel Path:
Right Channel Path:
Shared Power & Control:
To read any circuit diagram, you must first understand the pin functions. The IC uses a 22-pin SIP format. Pins are numbered left to right with the component side facing you. | Component | Value | Voltage Rating |
| Pin No. | Symbol | Function Description | | :--- | :--- | :--- | | 1 | IN+ (R) | Non-inverting input (Right Channel) | | 2 | VREF | Reference voltage (Decoupling) | | 3 | NF (R) | Negative feedback input (Right channel) | | 4 | GND | Signal ground | | 5 | VREF | Reference voltage (Internal bias) | | 6 | Bootstrap (R) | Bootstrap capacitor connection (Right) | | 7 | OUT (R) | Speaker output (Right channel) | | 8 | +Vcc | Positive power supply terminal (+V) | | 9 | -Vcc | Negative power supply terminal (-V) | | 10 | OUT (L) | Speaker output (Left channel) | | 11 | Bootstrap (L) | Bootstrap capacitor connection (Left) | | 12 | GND | Power ground | | 13 | NF (L) | Negative feedback input (Left channel) | | 14 | Mute | Mute control (via resistor to V-) | | 15 | Standby | Standby control (often tied to Vcc through resistor) | | 16 | IN- (L) | Inverting input (Left) – Not used in standard config | | 17 | IN+ (L) | Non-inverting input (Left channel) | | 18 | GND | Signal ground | | 19 | NC | No connection | | 20 | VREF | Reference | | 21 | VREF | Reference | | 22 | Muting | Secondary mute (often tied to Pin 14) |
Note: Early STK411-210E versions had 18 functional pins; later revisions use 22 pins, with pins 19-22 being duplicates of reference or mute lines.
The STK411-210E provides a simple yet robust solution for stereo amplifiers up to 20W per channel. The external circuit requires only a handful of passive components and a split power supply. Correct PCB layout and thermal management are critical for reliable operation. The circuit diagram presented here serves as a verified reference for prototyping or repairing audio equipment using this hybrid IC. Left Channel Path:
The STK411-210E belongs to a family of hybrid ICs that integrate pre-driver and output stages into a single multi-pin SIP (Single Inline Package). Unlike discrete transistor amplifiers, the STK411-210E provides consistent performance with minimal external components. Key features include: