Preamp to pedal

[wildebelor]

So I've seen a lot of preamp pedals that are in fact the preamp of a very famous amplifier in a pedal.
My question is, what is the process of getting it from preamp to pedal?
More specifically, what are the changes (if any) to the schematic in order to house it in a pedal?

If anyone cares to watch - this video has me a little stumped.
It claims to be an orange/matamp jfet emulator in a pedal
http://www.youtube.com/watch?v=DCmYwEOfoyA&list=UUGMPmA3eJCQDarO76GDJFDQ

I feel like in my mind, i'm just over complicating this for myself! 
Would really appreciate any help or input (HAHA GUITAR PUN) at all!

[aron]

One of the very first schematics that seem to have appeared and shared was Jack Orman's FET Preamp. You can do a search for it on this forum. It was renamed as the Mini Tubes Preamp. But it was definitely one of the first to embrace the concept or taking an amplifier schematic and then turning into a stomp box circuit.

[wildebelor]

So basically, I understand with a SS amp that there would be little changed in the preamp when transferring to an effect pedal because there aren't any tubes - am I right?
But when taking a tube driven amp and converting the preamp into a foot-friendly enclosure, one can either go the way of using the tubes as per the schematic or replacing them with jfets?

[aron]

Yes. Exactly.

[duck_arse]

the geezers doing the pedals "model" the characteristics of the valve amp stages. then they "emulate" the results with various biasing, clipping and filtering methods as applied to the basic characteristics of the jfets.

lots in the fetzer docs on the methods.