What do Oil Caps do and how do they effect sound?

Both solid state and tube amps produce a voltage. Current is what results when voltage is applied to a load, such as a loudspeaker. An amplifier might be capable of high voltage output under no load condition, but if it has little current delivery capability this voltage cannot be maintained into a load. Your preamp typically can output a signal of several volts, enough to play a speaker quite loudly, however if you hook it up to a speaker I doubt you would hear anything. The preamp can only deliver enough current to maintain the voltage into a load of several tens of thousands of ohms, not 4 or 8 ohms.

Tube amps have high "rail" voltage (plus and minus 400 volts or more) so that the output tubes can apply a high voltage to the primary winding of the output transformer. The output tubes cannot deliver a great deal of current. However, the output transformer is wound with a step-down turns ratio, so that the secondary output voltage is down to a handfull of volts, as appropriate for the speaker, but the necessary current capability is there. You might think of the output transformer as similar to the gearbox of a sports car, which permits a small engine reved up to 7000rpm, to accelerate the car from a standing start.

Correction in order here bomby:

"845 tube. This is a radio broadcasting type tube & the grid is biased at 1500V! "

No, sorry - not correct. max PLATE voltage on 845 is 1250v, and ASL doesnt' run them that hard. They would not bias the grid higher than the plate(!) and infact the grid is going to have about 70-80v of negative voltage applied, to run them in class A1.

And let's stop talking about 'rail' voltage w.r.t. tube amps - it's called B+. Rails apply to sand amps.

Eldartford makes a good point I was going to mention - B+ on tube amp is somewhat irrelavent in any case, since it's almost always going to go out through an OT, which has a massive step down ratio. (5000 : 8 or more)

The only situation which B+ would be used to drive speakers directly would be a high voltage transmitting tube output connected directly to the panel of an electrostatic loudspeaker. There were a few commercial attempts at this I think, none sold today that I know of. It's an idea which has a lot of merit but unfortunately is rather difficult to implement well, or at all. There are some more worthwhile and successful attempts being made by the DIY tube crowd, but that doesnt' apply to commercially available designs. Most of the time you would need a bigger tube that even 845 to do it as a SET amp (the only way it would be worth doing), meaning either a tube like a 212 or 849 or maybe 250/450TL, or else a more modern planar triode ala Eimac or Svet ceramic types possibly. (talking 1500-3500+v on the plate of those tubes)

-Ed

Thanks for all the wonderful response. It was a pleasure to read them all. This will definitely help me understand my new Cary tube preamp and also help me when deciding on a new amp and weather to go SS or Tube when the time comes.

Thanks for the correction Ed_sawyer. My bad for quoting the dealer without double-checking the info he gave me.

Bombaywalla, how did the ASL sound?