PaulS said:
Could you do that by changing the OT on let say the valve Junior attenuating the signal to a lineout or headphone signal ????
It's not so much that you have to change the OT itself. The original Herzog (which is what I am referring to, not the H-Zog of later years) used a Hammond 145 series OT. The OT on a Herzog has a load resistor (6ohm 10 watt) and a 1meg pot (to adjust the output), and then into a DPDT switch (to add or remove the Herzog from the circuit).
Any small amp could be modified to work like a Herzog, it would just be a matter of playing around with the load resistor values etc, to match your circuit. The original Herzogs didn't have a footswitch to turn it on or off, but it could be added fairly easily.