This circuit designed by Bruce and he has followed up his “OddWatt” project (EL84/6BQ5 Push-Pull) with the Oddwatt 225. The Oddwatt 225 is a scalable tube amplifier which will work with a number of octal tubes. In this build the driver stage is an SRPP with 6SL7 tubes and the output stage is a Class A UL SIPP with KT77 tubes. LM317 Regulators are used for the cathode CCS. source

When experimenting with tube amplifiers, you might be confused about the different modes of operation, like triode or pentode mode. Here is the developed circuits which you can build small Amplifiers based on 6P14/6BQ5/EL84 easily, and the output Power of 2.6 Watts is more than enough for home use. Also,the PCB included.With this PCB you can try out the different Modes by means of Jumper Wires.source

This is Push-Pull Class A based on 2A3 Stereo Amp.The input stage is comprised of a both halves of a 6SL7 octal dual hi-mu triode in a differential amp configuration with a 1ma constant current cathode load.The driver stage is comprised of a both halves of a 6SN7 octal dual medium-mu triode.source