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

I've seen testing where oil caps did marvelously well in terms of passing a signal with minimal degradation. Don't ask me what brands they were, as the brands weren't mentioned. Having said that, many find oil caps to be soft, warm and musical sounding. It is possible that they sound less "accurate" because many folks that grew up listening to lower grade SS gear were used to listening to non-linear distortions, which resulted in high end emphasis or "false detail".

As to why SS gear is typically rated for higher power levels than tube based designs, it has to do with current capacity. SS gear can typically pass a LOT more current. Since wattage equals voltage multiplied by the current in the circuit, greater current capacity with the same voltage will result in more total power output. Too much current will typically "blow" a tube faster than it will a transistor. Whereas tubes "open up" and fail, a transistor can blow a few junctions and still keep operating. It might not work as well as it used to under extreme conditions, but it is still working. As such, tubes are typically more fragile and either "work" or "don't work" acceptably. This is especially true of power output tubes in amplifiers. Sean
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Bombaywalla: I have pulled apart dozens of high current RF transistors and found blown junctions in them. All of these were still working albeit at reduced output due to the loss of internal conductors.

Many transistors use several junctions in parallel to handle the current levels needed, so blowing a few simply reduces the gain and max current potential. In effect, they have compacted several transistors into one case and they are all working together to share the load. Blowing one of the internal junctions inside of a transistor is no different than running a dozen external transistors in parallel. One, two or three might fail, but the rest of the circuit will continue to work at reduced capacity. That is, so long as the transistors that failed blew open and not shorted. If the transistors are running in matched push-pull pairs, noticeable distortion may occur, but the circuit can be made to work again by simply deleting the the mate to the transistors that went south. Once again, it will not be as powerful, but it will work and should maintain a reasonable semblance of linearity.

As far as tubes go, they are in a continual state of decline once they are fired up. While most experience a very slow and gradual death, it is more likely for a tube to "pop" at random than for a transistor just to up and let loose. On top of this, it is not uncommon for a piece of equipment to experience major damage when a tube lets go. If you doubt this, try searching the archives here pertaining to tube failure and start reading about the fires that have resulted.

Other than that, i agree with everything that Albert had to say. High rail voltages are a must if you want realism. Then again, you have to have enough current to maintain that level of voltage when under load or the rails will sag. As such, unless you have a speaker that is of noticeably higher than average impedance across the band, at least a reasonable amount of current will be required from the output section in order to maintain linearity, dynamic headroom and a solid soundstage. As the voltage sags under load, so does the impact and spatial characteristics. Sean
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