Well... We really put something like vowel in this case after "с" and "в". I would name it "eaten 'ы'". It goes from the lowest levels of throat. While saying "s" you begin to say "ы", but end it before it becomes distinguishable "ы" vowel. Tongue and teeth are saying "s" but throat is saying "ы".
There is no dependence on the following word.
It's better to hear...