The SSL may very well sound better/different when clocked externally but that suggests that the clock of the SSL isn't great at rejecting jitter. Don't forget that all of these products were designed and specced when clocked internally as well, not externally.
Re. What can clock to what and how, any digital device with a digital and wordclock output will happily feed another digital device a clock signal - The Hedd will clock to your SSL, your SSL will clock to your RME etc.
Regardless of my above comments having a clock distributor is no bad thing - they are great as a central source to clock all of your devices simultaneously rather than serially clock loads of digital devices to one another.
My point was please do not buy an external clock just to simply improve your sound! It's marketing rubbish and a technically flawed theory!
I say there needs to be better education of digital audio theory and clocking issues; there is a lot of discussion about analogue character and tone but what about good digital practise? This is always overlooked yet it is used by everyone (near enough). Set up your digital system correctly and you will bring the best (and maybe unveil the worst) out of your entire audio production setup.
...sorry, needed to get that off of my chest
