> curious why folks like this simple CF, instead of a WCF.
The WCF would run half the power current, but when you add the gain stage demand it isn't much less total current.
Output impedance is the same.
Output drive is about the same, though the 2CF needs more power current to do it.
The WCF has poorer power supply rejection (though this may not matter when the 12AX7-b stage runs the same supply).
The WCF needs a high-voltage coupling cap, idling about 350V. (The caps in there may touch 400V at start-up but idle at only ~200V; the wax-paper will last a long time.)
The high-voltage WCF will normally need separate heater supplies top and bottom: here the top cathode is at +223V idle (and tries to go to +400V at start-up!) and may peak over 250V on signal, the bottom cathode stays near ground. Of course if Peafy used the same heater supply for 12AX7 and 12AU7, still the same problem. If the 12AU7 has its own heater supply, the CF is fine. The WCF should have separate top and bottom supplies, which is not possible in a single bottle.
The perfect WCF has darn near zero distortion, which was not the goal here. However if the WCF is not in perfect balance, distortion rises. Here it is not in balance (the grid voltage should be more like 170V instead of 215V) and small changes in bias may cause audible change of tone. The CF is never balanced which means large change of bias gives little change of tone.
If you really nail a perfect WCF it hard-clips both sides. This off-balance CF will clip one side before the other, a more musical way to overload.
The average road-tech does not know what a WCF is, but can recognize a CF and maybe fix what broke.
So for the cost of 2mA extra current you get a simpler quieter cheaper more-stable design.