The conversion to the required analog signal must be the source device itself (TV, DVD player, game console, etc.) to make / support and thus spend an analog signal via the HDMI port, so that the connection to older devices such as AV or stereo Amplifiers also what is.
If the source device does not have this feature (sometimes carefully the setup and instructions scour) unfortunately has to a more expensive D / A converter (digital / analog converter) to be gripped which then the HDMI signal with an electronic system to a usable analog signal converts.
I go once assume, because know I will not do it and do not know now the HDMI signal circuits that has the converter for converting the signal via an additional power supply (PSU).
However, I do not rule out that already has the HDMI connector, a live wire for just such purposes. At least it would not be practical, provided that would incur no signal interference ...
That's all ... ;-)