I'm focusing mostly on Nelson Pass' published plans because they're simple and therefore somewhat easier to build. Design elegance also tends to lead to better sound, since there are fewer elements corrupting the signal. Still, building an amp requires mechanical and electronic aptitude and usually a lot of time and effort finding parts. It's certainly easier to buy a commercial amp, but it's perhaps not as rewarding as building your own. All amps run pure Class A or heavily Class A biased Class AB. All plans have appeared in Audio Amateur magazine or it's successor audioXpress.
|Zen||1||Single-Ended||MOSFET||Moderate||10W||20%||Very Simple, Active Current Source, Capacitors on input and output|
|Son of Zen||1||Balanced Single-Ended||MOSFET||None||10-50W||5%||Balanced Power Differential Pair, no coupling capacitors, resistor current sources|
|Hoffman||2||Balanced Input, Single-Ended Output||MOSFET||Moderate||35W||20%||Current Sources for both stages, Split Power Supplies, No Capacitors on output|
|A40||4||Single-Ended Differential Pair Input, Voltage Gain Stage, Darlington Push-Pull Output||Bipolar||Moderate||40W||40%||No coupling capacitors, Current sourced input and voltage gain stages|
|A75||2 to 3||Balanced Input, Variable-to-none Cascode Driver, Push-Pull Output||MOSFET||Adjustable to None||75W (into 8 Ohms, 150W into 4 Ohms)||45%||Gain contribution of Cascode driver stage adjustable down to none, resulting in adjustable feedback and distortion characteristics ranging from a 2 to 3 stage design. Current sourced differential input.|