SomeThing is not right with the crosstalk numbers. Either your methodology is flawed, or there is a problem with your Mini3.   I would inspect the soldering on the Mini3 with a loupe. High resistance at the phone jack or ground channel amp could elevate the crosstalk numbers.

Hook up your voltmeter to the power and measure the voltage with the power supply connected to the amp, then slowly and carefully move your hand close to the mosfets and observe the voltage. DO NOT TOUCH ANY EXPOSED WIRES!!!

Disconnect the power supply from the amp and measure the voltage at the power supply plug.

^Looking good there Pierre.   The volume knob turned out looking pretty nice, I think.   Did you get the high power supply voltage down, or is it still running about 68v or so?   I would like to see about 12v to 13v across the heaters. I'm not sure how they will last with almost...

is your power supply rated for 110vac input or 220vac?  

It would be easier if you did what Nikongod asks.   Then post your findings.

Measure resistance between RCA signal input jack(the center pin) and circuit ground.

Check the resistance between the input RCA jacks and ground.   68v is a bit high for your power supply. Is it 48v dc or ac?

Allow the tube heaters time to warm before taking measurements.    

Measure between the grid and cathode for voltage.   Measure voltage between the gate and source on the mosfets.

Your power supply is 48v?

Check some voltages and compare the 2 channels.   Power down and check the resistance from input RCA jacks to the grids, and to ground. Again, compare channels.

Yep, wire according to the diagram you posted earlier, while looking at the bottom of the socket.

Nikongod is right. The sockets should be wired looking at the bottom of the tube. They are backwards.

Quote: You are not finished in this pic? It looks like nothing connected to pin 1(plate) and a wire going to pin 9(should not be a wire on pin 9)   Up close pics would help.