Hello all, This is my first post in this forum. Hope can get some constructive help from the community. I did some testing with some radios which is actually a double ended circuit (BTL), meaning it has the spk+ and spk- port. When I want to connect it as a single ended circuit, meaning the spk - short to ground, the audio is muted. The only way for it to work is by adding a capacitor in line with the spk+ which is the DC blcok. I search through the internet and found similar information saying that the DC block is required in order to work. Can I know why ? what is the reason behind? Thanks, appreciate the view and help.