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The Driver Tube;
The driver tube is the least understood tube in an amp. If you are putting in matched sets of output tubes (and you really should be) then you are wasting your time and money without a Driver Tube that has been picked for this special job.
Just about every amp with 2 or more output tubes uses a driver tube. Why it is so important is because this tube takes a single signal voltage, and splits it into two. There are actually 2 separate amplifiers in a 12AX7 and in a 12AT7. If each amplifier section in it are working at the same potential - great! But they hardly ever do... so, you need to find one.
As far as I know, no one markets a "driver tube" for musicians, however I do. That's because when I
purchase tubes, I sort them for where in the amp they would perform best. This symmetry in the driver tube allows the 'matched' output tubes to see the same input signal voltage levels, and in turn deliver matching output voltages. When all this and properly biased, the tubes will sound better and last longer. Be sure to read the section on matched sets to fully grasp this vital aspect of your amp.
Preamp Tubes V.S. Output Tubes;
This is where the tone really happens: in the preamp. Read more about that in "ABOUT PREAMP TUBES". Most amps don't depend on output tube distortion to generate the tone. There is an audible difference in the way preamp tubes distort and the way output tubes distort.
Preamp tubes are capable of much higher levels of distortion (safely), and tend to sound like a finer grit of sandpaper than the course distortion of an output tube. For amps that use EL34's (6CA7), EL84's (6BQ5) like Marshall and Vox; these tubes are likely to impart their own tone and or type of
distortion under normal operating conditions. For almost all Fender circuits you will find the 6L6/5881: this is a workhorse clean tube. When working properly, the output tubes do a good job of NOT imparting their own tone, or distortion. In some Marshall's, you'll find 6550's; these tubes are the big brother to the 6L6/5881. They extend the treble a fair amount, and by comparison can be shrill. They also allow you to hear what's going on in the Marshall preamp circuitry with much more detail. Its a good rig for most Metal genre's, as articulation is a key component to a great sound. Its also a great tube for jazz players. The classic Marshall tone is 3) 12AX7's with 4) EL34's for the Rock Arena, for the blues and proto-rock glean its the 40 to 50 Watt version (as above but only 2) EL34's.
Power Tubes;
Just to clarify, Output Tubes AKA "Finals" although they do a lot of work, are really not "Power" tubes, as they are often referred to. I'm too old to try to change the world, but, Power Tubes are rectifier tubes, and (almost never seen in audio) regulator tubes. In both cases "power tubes" refers to tubes that are part of the power supply. Output Tubes are not part of the power supply, so it doesn't make sense to call them "Power Tubes".
Examples of power tubes are 5AR4/GZ34, 5Y3, 5V4, 5U4, A03.
Examples of output tubes are 6L6, EL34, 6V6, EL84, 6550.
About Preamp Tubes;
First off, nobody's tubes sound any better than anyone else's. Its entirely a matter of taste. From one 12AX7 to another, you will hear differences in tone, dynamic range, and distortion characteristics, if you listen to them at clean, low volume settings. If you want to know what they are really doing behind your wall of distortion, first give them a critical low volume listening. If you lack the discipline to do this, then you will never learn what all the different tube qualities are. Its great that you like to play loud - whatever, I do too.
Tone; Some preamp tubes sound thin, some dark. Some lack midrange, some are rich and fizzy.
Dynamic range; Some are accurate, percussive tubes, others are compressed. One may sound too aggressive and the other too squishy. They both sound good, but one will perk your ears up and make you say "Yea, that's what I've been looking for, that's been the missing ingredient!" Compression is not a bad word. In tubes, the effect is so natural and transparent that you don't hear it as compression. It simply has a different feel, which is what you should be focussed on. It can tame the harshness of one amp, but add the punch needed for another amp.
Distortion characteristics; How quickly a tube is driven into clipping, and whether it then gets smoothly rounded off or generates harmonic overtones determines whether the tube simply compresses or goes into distortion. What that distortion sounds like is affected by the tonal characteristics of the tube, and if it is also audibly compressing. What range of notes gets distorted most easily has a great deal to do with your final product in terms of tone. This is because in guitar amps distortion is overtones, and overtones can be in an area where fundamental notes lay as well.
To hear the differences you need only one of each type, and listen to each one in the socket nearest the input jack. Here the preamp tubes' effect will be the most evident. Learning the way you can refine the tone of your amp with tubes is fun, inexpensive, and worthwhile.
