The process of producing history necessarily involves raw materials; history can't be produced out of nothing. And what sources one looks at still determines what type of history you do more than the way you read those sources. This is not the same thing as saying that the source yields a clear and uniform meaning, which is rarely or never true.
As far as I see it, there are two motivations behind the act of studying history. The first is an interest in the material of history. Whatever one thinks about the existance or observability of the past "wie es eigentlich war," there exist traces, or signs, which come from the past, and that these are the materials which lie at the heart of the act of producing history. Most undergrads, most people in fact, assume that history is the sum total of all these materials, and that historians are interested in these for their own sakes. I can't deny a childlike fascination with looking at something that possibly no other living person has seen before.
The second motivation is an interest in the process of historical change. No one really knows what if anything lies at the heart of movement in history. Hegel thought he did. Others have ideas. But any answer to this question will always depend on the way in which you shape the materials of history into patterns, and thereby give them meaning. This is of course an entirely unconscious activity, most likely a linguistic one. See Hayden White on this.
There are times when one needs to ignore Hayden White and the postmodernists, though, and pretend that the past actually exists in an intelligable form. Nietzsche, as always, strikes a balance here by reminding us that it's all a fiction ("truths are illusions which we have forgotten are illusions") but that its a necessary fiction.
Go to the sources. They are true. They will do the work for you.