I requested preamp tube functions/positions for my amp & got this email: "Both pre-amp tubes are 12AX7s. The tube on the right (closest to the corner) is V1. V1 is the first tube in the signal chain and it feeds the tone controls. The tube on the left is V2. Half of V2 is a recovery amplifier for the reverb and effects loop. The other half is the split phase inverter (aka cathodyne phase inverter). " Does this make sense? Can 'half' a tube function as a PI?