Speaker protection with uPC1237

I was using IC uPC1237 for speaker protection in almost all my power amplifiers, because schematic is very easy to build with few external components.



Here is the latest version of the schematic that I use:

A transistor and LED were added to indicate when speakers are switched off.
The whole part with R1, R2, R3, R4, Q1 and J1 is optional and protection module will work without them.

The C1 value may be increased if there is false activation with high output signal level from amplifier. It is also preferable if C1 is non polar (bipolar), but these are harder to find, so if it is a polar, then put one with higher voltage - at least 50V
With these values of elements schematic will work with 24VAC, 32VDC, and will activate when there is more than ± 2VDC in output signal. Initial mute time will be around 3-4 seconds.
There are formulas in the schematic to calculate the values of the resistors for different supply voltages.

Bellow is a diagram how to connect speaker protection module with an amplifier.

A little older version of the protection module.

Here is a link for downloading an archive with PDF files of the project: DC Protection.rar
Use it on your responsibility.

UPDATE: 29.01.2019
The link for the project files is fixed and the archive include the latest version of PCB + Gerber files.