a tube primer for guitar and bass players - Guitar Amplifier Blueprinting

The Output Tubes – The Pentodes and Beam Pentodes
A typical pentode trace.
Many people believe that a 6L6 is a 6L6, an EL-34 is an EL-34, etc. This is far from the case. Each of these tubes have different sonic
features. Many folks ask the difference between an EL-34 and 6L6. In a nutshell, I guess one can say that the EL-34 has more of an
articulate mid-high and high end articulate response. If you like a lot of high end harmonic articulation and distortion with a high degree of
articulation, than perhaps this would be the preferred tube. In the case of the 6L6, there are stronger lows and mid-lows, and for mass
overall output, this may be the taste for you. Some folks love the 6550 and KT-88 tubes in amps if they get most of their tone and
distortion from pedals or effects. These tubes yield a lot of clean headroom.
Many ask me which is “more powerful” between the EL-34 and 6L6. Some feel the EL-34 is stronger, due to the 100 watt Marshall or
Hiwatt type amps of the past. This is not the case in reality. These amps at times had higher plate voltages, so at times produced more
wattage for a given tube type or tube set. A decade or so ago, Fender had an amp called the “75” that produced about 75 watts out of a
duet of 6L6’s, as one example.
There will be charts as we progress, that show the same types of tubes used in the same circuits using the same plate voltages and bias
voltages. The output is in milliamps. A tube with a higher reading, is more powerful than a tube with a lower reading. It is as simple as
that. This does not mean a higher number is “better” … there are many other aspects regarding tone. This is just a simple power
measurement for the folks asking me which tube is stronger. This does not indicate or mean that a higher current tube is better in any way.
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