k so im have no idea how they work. all i really no is that they have different sections to them and you can get better tones out of them sometime.
can anyone explain how they work and how to set them up.
You basically need 2 units: a pre amp and a power amp.
Be prepared to pay a lot more than a normal head, but you generally get better sounds and they are more versatile.
Look at ENGL pre amps and Mesa Boogie power amps.
Jackson KV 2, Jackson COW 7 (both in B), Jackson Demmelition V
Bogner Überschall (blue rev)
Marshall 1960B Vintage (2x V30 & 2x G12T75)
TC Electronic G Major
BBE Sonic Maximizer 422A
Weber Mass 150w
ISP ProRackG
T.Racks Dinopower
Ventor pretty much summed it all up for you.

Your normal amp head has two parts... the preamp part, and the poweramp part. The preamp part is the part of the amp that defines your sound and tone, this is the part that handles your gain, your EQ, etc. The poweramp part is much simpler, this is literally the 'amplifier' part... the poweramp takes the signal your preamp creates, and then amplifies it (so it can be loud enough to be heard through speakers). This 'amplified' signal is then sent to your cab. (in a combo, the same thing happens, except instead of going off to your cab, it just goes directly into the connected speakers)

Racks are versatile... because you buy different preamps, and different poweramps, and hook them up together. You can sort of, "customize" your own amp, by doing different preamps into different poweramps. And you can get very creative with switching systems, and even use multiple preamps, multiple poweramps, etc.

But... this versatility comes at a price. For high-end preamps and poweramps, you can expect to spend at least $1,000 and more.

If you are truly interested... there are a number of companies that make quality rack gear. Mesa makes great poweramps in a number of varieties (ie, different power output, channels, etc). Mesa also makes some great pre's (Recto Pre, Tri Axis). And as Ventor points out, Engl also makes quite a few pre's (they have a cheap one that you can find for like ~$500... and an expensive one that's ~$2,500, and a few inbetween). Marshall also makes a nice pre, as does Soldano, ADA, and a number of other companies.

Do a search on UG for "rack", "rack gear", etc... you'll find a decent wealth of information to get you started and informed.
CyBerAliEn nailed it pretty spot on.

*quick note to him, I noticed you say you're getting an Engineering degree and you're in AZ, are you going to ASU Polytechnic? That's where I'm going next year. PM me or whatever if ya see this so we don't clutter up TS's thread Oh and damn, your rack is intense! lol*
Quote by Dave_Mc
I've had tube amps for a while now, but never actually had any go down on me
Quote by jj1565
maybe you're not saying the right things? an amp likes to know you care.

Best rack system i have ever seen is the Randall MTS and Poweramp section. 4 modules, two different power tubes and all switchable at the press of a button. Also you can link modules.

There is a video on you tube check it out.
i have a setup that i am looking to sell.

its a mesa 290 power and mesa formula pre. w/ 6 space rack and furman power conditioner. PM if interested