Modified Fender Deluxe
 

I recently completed a modified Fender Deluxe tube guitar amp per the attached schematic. The main distinguishing feature of the mod is the phase splitter. Rather than using the traditional Schmidt long tail, I used a constant current source (Vishay J505 1.0 ma) splitter which provides considerable gain and an absolute perfect split. The Schmidt splitter provides unity gain and does a poor job as a splitter. Due to the extra gain, you will need a master volume between the recovery tube and the constant current splitter. Sounds absolutely great.

I thought the whole point was to have an unbalanced split to help generate the distorted valve sound you're after? - with many designs even having different resistor values to ensure it.

But even with a 'perfect' splitter, the output valves are going to have different gains anyway, so it's still not going to be accurately balanced.