Two circuits from Elektor LFA150 amp project, for protecting speakers against DC in case of amp failure or one power supply polarity missing. Never used because I was given another mono amp from Elektor and could not gather all the parts to build a stereo amp quickly, then I thought to adapt DC protections from another Elektor project, but it did not work with different power supply voltages. Homemade PCB's. Not built with the best looking and rather small components like on Elektor's cover pages, sold as-is. Please make an offer.