There does seem to be some confusion here.
The PT-2 can deliver 60mA of DC high-voltage current. If you stay with the 50mA 2A3 current used in the Paramour, there is 10mA left, which is enough for a twin-triode shunt regulated driver - we'll have the new board set up for the 5670 in the Paramount so that's a good choice, but others can work.
If you raise the 2A3 current to 55mA, which is more optimal for the 3K impedance, then you have only 5mA left and can't shunt regulate the driver. Also, the BCP-15 cannot support more than 50mA of plate current. So I'd stick with the 50mA/300v of the original Paramour; the increased inductance of the BCP-15 goes a long way to make up for the slightly off-optimum operating point.
The SR45 replaced the 2A3 with a 45, cutting the output power in half. The 45 operates at 250v and needs only 36mA, so there is enough current left over (just barely) to shunt-regulate the entire amp, not just the driver stage. We produced a very limited run of semi-kits a couple years ago for this - semi-kit meaning that there was almost no manual and not much developmental testing. It was intended for advanced experimenters. We never saw enough potential sales to justify the full development effort, but we liked the sound so much we wanted to make something available to at least a few.
I posted a few minutes ago in the other thread, sorry for the confusion and I hope this note helps make sense of my other one!
