Speaker protection board (balanced, stereo, dual-mono).

SKU: N/A Category:


The Guardian-686 is intended for use in bridged/balanced/BTL amplifiers, such as the Modulus-686. The Guardian-686 is a balanced, dual-mono version of the Guardian-86 circuit. The features of the Guardian-686 are listed below.

  • Balanced dual-mono construction – use with balanced/bridged/BTL amplifiers or stereo single-ended amplifiers. For a mono version, please see the Guardian-86.
  • Compatible with the Modulus-686 and similar balanced amplifiers, as well as stereo and dual-mono builds of the Modulus-86Modulus-286, LM3886 Done Right, and other amplifiers with single-ended outputs.
  • No relays! All switching is done with MOSFETs for the lowest distortion.
  • No relay contacts to wear, thus, no change in performance due to aging.
  • Adds no measurable distortion.
  • Floating photovoltaic MOSFET driver ensures consistent good performance throughout the full swing of the output signal.
  • 5-second delay on power-up. Output disabled when supply voltage falls below 22 V. This drop-out voltage may be changed by changing two zener diodes.
  • Input: Molex Mega-Fit connector for easy connection to the Modulus-286, Modulus-686, and LM3886 Done Right, and terminal blocks accepting up to AWG 10 (5.2 mm2) wire for use with the Modulus-86 and other amplifiers.
  • Output: Terminal blocks accepting up to AWG 10 (5.2 mm2) wire and four 4.3 mm diameter holes at ¾” (19 mm) pitch for direct mounting onto the speaker output terminals.
  • 2.50 × 3.25 inch footprint.
  • Gold plated circuit board. Designed and manufactured in Canada.

The full circuit description and additional details, please see the Guardian-686 description page.