The Modulus-286 is a 125 W, Class-AB, LM3886-based power amplifier with error correction provided by an LM4562 precision opamp. It delivers clear, precise, and fatigue-free sound; and distortion below 1 ppm even at full power. This third revision of the Modulus-286 features improved performance, in part due to the further optimized PCB layout.

Modulus-286 Rev. 3.0 is slightly smaller than its predecessor, but shares the same mounting hole locations, allowing for a direct replacement.

The wiring harness necessary for connecting to the Modulus-286 is included.

Technical Documentation

Data Sheet Design Documentation

• Description
• Key Specifications
• Circuit Topology

• Key Features

  • Fully assembled module made in Canada from parts sourced from authorized distributors in Canada and the USA.
  • World class performance ensured by an error correction circuit with local, low-noise power supply regulators.
  • Power supply agnostic by design. High performance is attained with unregulated power supplies and with switch mode supplies.
    
  • Differential (balanced) input which eliminates hum and ground loop issues. Can be used with single-ended (unbalanced) sources as well.
    
  • On-board EMI/RFI input filter and ESD protection.
  • Four-layer PCB optimized for high signal integrity. All ground management is handled on the PCB.

  Build difficulty (1-5): 1 (easy).

  The build video below shows you how to build a Modulus-286 stereo amplifier. Please watch the video to gauge the skills needed.
  

• The graph below shows the THD+N vs output power for the Modulus-286 Rev. 3.0 for 8 Ω and 4 Ω load. The sharp jumps in the graph are caused by range switching of the APx555 used for the measurement.

  

  The table below lists the key specifications for the Modulus-286 Rev. 3.0. For the full specifications, please see the data sheet on the Downloads tab.

  Parameter	Value	Notes
  Output Power	125 W	4 Ω, < 0.01 % THD+N
  Output Power	65 W	8 Ω, < 0.01 % THD+N
  THD	≤ -130 dBc (0.000032 %)	50 W, 8 Ω, 1 kHz
  Multi-Tone IMD Residual	≤ -140 dB Ref.: 50 W	AP 32-tone, 50 W, 8 Ω
  Total Integrated Noise and Residual Mains Hum	13.0 µV RMS	20 Hz - 20 kHz, A-weighted
  Gain	20 dB	26 dB selectable by jumper
  DC offset	≤ ±320 µV ≤ ±2 mV	Typical Guaranteed by design
  Finished Assembly Dimensions and Weight	101 × 60 × 40 mm 100 g	(W × D × H)
  Recommended power supply	Power-86 with 2x25 VAC, 200-300 VA power transformer for stereo
  All parameters are measured at a supply voltage of ±36 V DC.

• The block diagram of the Modulus-286 Rev. 3.0 is shown below.

  

  The Modulus-286 Rev. 3.0 uses an LM4562 to form a balanced composite amplifier with two LM3886 in parallel. An LM4562 is used for the differential input. 

  The differential input can be used both with differential signal sources (XLR) and with single-ended ones (RCA).

  The Modulus-286 is power supply agnostic by design. This is unique to the Neurochrome Modulus amplifiers. Due to the error correcting composite amplifier topology, the Modulus-286 performs as well on a traditional unregulated linear power supply or a switch mode power supply (SMPS) as it does on a well-regulated laboratory power supply.

  The PCB layout is crucial at the performance levels attained by the Modulus-286. The four-layer PCB employs differential signal routing and carefully designed copper pours and planes to ensure optimal circuit board performance.