RetiredUnit1
Well-known member
The main difference is that a champ uses a cathode bias for the power tube. This never needs adjustment as it is a RC, resistor capacitor combo. Normally used in amps with less power.A smaller amp has all the same parts as a bigger one. Building a champ won't be much different than a deluxe so get what you want
edited: another difference: the champ only has one power tube and is what is known as an open ended class A, so the output transformer is different since it has to feed from only one tube. Normally in a push pull the signal goes through a phase inverter. Half the signal goes to one side of the tubes, the other half goes to the other side. Since the phase is always up on either left or right there is always sound. Since it's very difficult to match tubes, there is always a bit of shimmer to a push pull tube amp. I'm not exactly sure how one tube works, something to read up on that I never bothered with, lol.
Larger amps use a negative polarity to keep the tubes running (usually) at 70% or less of their rated power. These used to have just a resistor in the days gone by that was calculated at spec. Newer tubes are so far out of spec that a trim pot is added while reducing the resistor to have a range above and below spec.
Not a huge difference but worth mentioning. Adjusting this trim pot is what is known as biasing the tubes. It's at the end of the document link I posted earlier for the instructions for the model 1987 plexi. So for anyone that ever wanted to know how to bias tubes, just read that last part of that doc. starting page 28
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