Be careful what you mean by "preamp". A Mesa Boogie Tri-Axis is considered a preamp as is a Neve 1073. (The Tri-Axis is a guitar preamp and the Neve 1073 is a mic preamp.) These are very different gadgets even if their principal function is to boost the gain of a low-level signal.
By mentioning guitar it's presumably you will want your circuit to overdrive or distort. Is this correct?
Brandon