Last year I made different Main stages and extra driving stages. This time I change my Projects into integrated amps with Driver and Volume control.

Here is my Project with PX25 here from Tungsram P27/500.

As Driver I use EF37a. I have quite a lot and different types.

The rectifier is GZ34.

The amp is completely silent and plays like a PX25 should do. Big soundstage with much details and very musical.

The C-core OPT are fitting very well and let the sound go deep enough.


The holes for the octal sockets have been there already, as i planned actually to change between PX25 and 300B. Now its just PX25 with EF37a, which could also just be switched with 6J7G.


PX25 and EF37a, is just a great combination.

First I had 6SJ7 in it, but then a friend brought me to the idea of 6J7G and so only the cap for the Grid and some soldering on the sockets and it was ready to put in 6J7G or EF37a, i also have STC  5A/157D, all this driving Pentodes are possible to use without any change intern.


The PX25 is running with 400V on the Anode and 29V on the Katode. Kathode resistor is 600 Ohm.

the EF37a is running with 125V on the Anode, 75V on Grid 2 and 2 V on the Kathode. Kathode resistor is 900 Ohm