Re: Question: Number of tubes & power output...
Dirfferent tubes have differnt usages. Tubes from different manufacturers can sound slightly different.
Preamp tubes are the small tubes. They take the millivolt output of the guitar's signal and amplify it to about the level of 1 volt. The 12A?7 tubes AU7, AT7, AY7, AX7 have different gain factors: a 12AU7, IIRC, has a gain factor of 20, while the commonly used 12AX7 has a gain factor of 100. Each of these tubes has two sections--two tubes in one.
Power tubes are the big bottles in your amp that do all the work, taking that 1 volt signal and making it become roughly 30 volts. EL34s are common in European amps, while the 6L6 and 6V6 types were the choice of many American companies. Another favorite of both sides of the Atlantic is the EL84. All of these tubes have different outputs, different operating parameters, and different tones and characteristics.
In many modern amps like Mesa Boogies and the Marshall TSL 2000, the preamp tube circuits are overdriven to produce a distorted sound. Back in the early days of tube guitar amps, there were no "master volume" circuits or "cascading preamps". In fact engineers worked very diligently to AVOID distortion. Tubes aren't the only part of the equation, though--the engineer has to make choices in his circuit design to best accomplish his goal.
When an amp is driven hard into distortion, lots of things start happening in that circuit. Single coil pickups, typically don't have the high output of a humbucker, so while the SC guitars stays cleaner at high volume, the HB guitar can overload the first input stages of the amp causing the tube to distort. The same thing happens to the amps power tubes, as voltages swing, the amp takes on a lively three-dimensional feel--if the engineer has done his job well with the rest of circuit. Some we like, some we don't. Some distortion is pleasing, often times it isn't.
Some of us become technical geeks, but try to remember that the technical specifications don't tell the real story about any musical instrument. Concentrate on the sound, the feel, the quality.
Does it meet your needs? Does it play with enough clean volume and headroom? Is the distortion pleasing?
And then you have to deal with the more mundane things, like how am I gonna pay for this? Can I read the knobs? Can I lift it? Will it fit in my car? Will my mom and dad kill me when they find out I took money out of my college fund to buy a guitar amp?
As you read more and more, the technical understanding will come, even though at times, it may seem like magic. Remember though, the real magic comes from the process of transforming your creativity and communicating your musical ideas to your audience. The guitar and the amp are just tools to accomplish that goal.
Bill
thanks Bill!
